Updated on 2024/05/27

写真a

 
NODA, Suguru
 
Affiliation
Faculty of Science and Engineering, School of Advanced Science and Engineering
Job title
Professor
Degree
Ph.D ( The University of Tokyo )
Profile
1994.03 Graduated from Department of Chemical Engineering, School of Engineering, The University of Tokyo (Bachelor).
1996.03 Graduated from Department of Chemical System Engineering, Graduate School of Engineering, The University of Tokyo (Master).
1996.03 Graduated from Department of Chemical System Engineering, Graduate School of Engineering, The University of Tokyo (Ph.D).
Ph.D Thesis "Generation and Reaction of Gas-Phase Hydroxyl Radicals at Gas-Solid Interfaces." Advisor: Prof. Masayoshi Sadakata.
1999.04 Assistant Professor, School of Engineering, The University of Tokyo.
(Belonged to Komiyama Lab. and Yaguchi-Okada Lab. at Department of Chemical System Engineering)
2007.06 Associate Professor, School of Engineering, The University of Tokyo.
(Belonged to Yaguchi-Noda Lab. at Department of Chemical System Engineering)
2012.09-now Professor, Faculty of Science and Engineering, Waseda University.
(2009.10-2013.03 Concurrent researcher, PRESTO, JST)

Research Experience

  • 2012.09
    -
    Now

    Professor, Waseda University

  • 2007.06
    -
    2012.08

    Associate Professor, The University of Tokyo

  • 2007.04
    -
    2007.06

    The University of Tokyo   The Graduate School of Engineering

  • 1999.04
    -
    2007.03

    The University of Tokyo   The Graduate School of Engineering

Education Background

  • 1996.04
    -
    1999.03

    The University of Tokyo   Graduate School of Engineering   Department of Chemical System Engineering  

    Ph.D course

  • 1994.04
    -
    1996.03

    The University of Tokyo   Graduate School of Engineering   Department of Chemical System Engineering  

    Master course

  • 1990.04
    -
    1994.03

    The University of Tokyo   Faculty of Engineering   Department of Chemical Engineering  

Professional Memberships

  • 2017.10
    -
    2023.09

    Science Council of Japan

  •  
     
     

    The Engineering Academy of Japan

  •  
     
     

    The Carbon Society of Japan

  •  
     
     

    The Fullerenes, Nanotubes and Graphene Research Society

  •  
     
     

    Materials Research Society

  •  
     
     

    The Japan Society of Applied Physics

  •  
     
     

    The Society of Chemical Engineers, Japan

▼display all

Research Areas

  • Nanobioscience / Chemical reaction and process system engineering

Research Interests

  • Materials Processing, Carbon Nanotubes, Graphene, Silicon Thin Films, Chemical Vapor Deposition, Physical Vapor Deposition

Awards

  • The Okuma Academic Encouragement Prize, Okuma Memorial Academic Prize 2020

    2020.11   Waseda University  

    Winner: Suguru Noda

  • Next-Generation Core Researcher

    2020.04   Waseda University  

    Winner: Suguru Noda

  • 平成29年度特別研究員等審査会専門委員(書面担当)表彰

    2018.08   日本学術振興会  

    Winner: 野田 優

  • 2016 EDS Paul Rappaport Award

    2017.12   IEEE Electron Devices Society   "A color-tunable polychromatic organic-light-emitting-diode device with low resistive intermediate electrode for roll-to-roll manufacturing"

    Winner: T. Tsujimura, T. Hakii, S. Noda

  • Teaching Award, Waseda University

    2016.04   Waseda University   "Material Process Engineering"

    Winner: NODA, Suguru

  • Teaching Award, Waseda University

    2014.04   Waseda University   "Material Process Engineering"

    Winner: NODA, Suguru

  • Distinguished Lecture in Chemical Engineering, Hiroshima University

    2014.04   Department of Chemical Engineering, Hiroshima University  

    Winner: NODA, Suguru

  • The SCEJ Award for Outstanding Young Researcher

    2006.03   The Society of Chemical Engineers, Japan   "Understanding Spontaneous Structure Evolution in Thin Film Processes and Rational Synthesis of Nanomaterials"

    Winner: NODA, Suguru

▼display all

 

Papers

  • Prior oxidation of Ni substrates increases the number of active sites in Ni3S2 obtained by sulfidation and enhances its multifunctional electrocatalytic activity

    Anantharaj Sengeni, Suguru Noda

    Journal of Materials Chemistry A   12 ( 10 ) 5793 - 5804  2024  [Refereed]

    Authorship:Last author

     View Summary

    Pre-oxidation of Ni substrates before sulfidation resulted in a highly active multifunctional anode catalyst capable of ensuring energy-saving hydrogen production by water-small molecule coelectrolysis.

    DOI

    Scopus

  • A stable full cell having high energy density realized by using a three-dimensional current collector of carbon nanotubes and partial prelithiation of silicon monoxide

    Tomotaro Mae, Kentaro Kaneko, Hiroki Sakurai, Suguru Noda

    Carbon     118663 - 118663  2023.11  [Refereed]

    Authorship:Last author, Corresponding author

    DOI

    Scopus

  • Prompt and effective purification for thin single wall carbon nanotubes by dry process using ferric chloride

    Yuki Kuwahara, Fahmida Nasrin, Mitsuharu Tabuchi, Hiromichi Kataura, Ryota Yuge, Suguru Noda, Takeshi Saito

    Carbon   213   118207 - 118207  2023.09  [Refereed]

    DOI

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  • Safe and damage-less dry-purification of carbon nanotubes using FeCl3 vapor

    Hideaki Tanaka, Takuma Goto, Kohki Hamada, Kei Ohashi, Toshio Osawa, Hisashi Sugime, Suguru Noda

    Carbon   212   118171 - 118171  2023.08  [Refereed]

    Authorship:Last author, Corresponding author

    DOI

    Scopus

    2
    Citation
    (Scopus)
  • Electrochemical Dealloying-Assisted Activity Enhancement: The Next Big Thing in Water Electrosplitting!

    Sengeni Anantharaj, Suguru Noda

    Nano Energy     108624 - 108624  2023.06  [Refereed]

    Authorship:Last author

    DOI

    Scopus

    8
    Citation
    (Scopus)
  • Stable and high-capacity SiO negative electrode held in reversibly deformable sponge-like matrix of carbon nanotubes

    Tomotaro Mae, Kentaro Kaneko, Mochen Li, Suguru Noda

    Carbon   209   118014 - 118014  2023.06  [Refereed]

    Authorship:Last author, Corresponding author

    DOI

    Scopus

    3
    Citation
    (Scopus)
  • Appropriate properties of carbon nanotubes for the three-dimensional current collector in lithium-ion batteries

    Kentaro Kaneko, Mochen Li, Suguru Noda

    Carbon Trends   10   100245 - 100245  2023.03  [Refereed]

    Authorship:Last author, Corresponding author

    DOI

    Scopus

    4
    Citation
    (Scopus)
  • The importance of carefully choosing vertex potentials in hydrogen underpotential deposition

    Sengeni Anantharaj, Suguru Noda

    Materials Today Energy   32   101234 - 101234  2023.03  [Refereed]

    Authorship:Last author

    DOI

    Scopus

    3
    Citation
    (Scopus)
  • Ambiguities and best practices in the determination of active sites and real surface area of monometallic electrocatalytic interfaces

    Sengeni Anantharaj, Pitchiah E. Karthik, Suguru Noda

    Journal of Colloid and Interface Science   634   169 - 175  2023.03  [Refereed]

    Authorship:Last author

    DOI

    Scopus

    8
    Citation
    (Scopus)
  • A tri-functional self-supported electrocatalyst featuring mostly NiTeO3 perovskite for H2 production via methanol–water co-electrolysis

    Sengeni Anantharaj, Mochen Li, Roshini Arulraj, Karthik Eswaran, Sara Fidha C. M., Rajini Murugesan, Arthanareeswari Maruthapillai, Suguru Noda

    Chemical Communications   59 ( 85 ) 12755 - 12758  2023  [Refereed]

    Authorship:Last author

     View Summary

    An extended hydrothermal treatment of Ni with restricted Te content resulted in a highly active tri-functional electrocatalyst performing the HER, OER, and MOR in alkaline medium.

    DOI

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    2
    Citation
    (Scopus)
  • The reference electrode dilemma in energy conversion electrocatalysis: “right vs. okay vs. wrong”

    Sengeni Anantharaj, Prince J. J. Sagayaraj, Manova Santhosh Yesupatham, Roshini Arulraj, Karthik Eswaran, Karthikeyan Sekar, Suguru Noda

    Journal of Materials Chemistry A   11 ( 33 ) 17699 - 17709  2023  [Refereed]

    Authorship:Last author

     View Summary

    A critical experimental analysis finding the answer to the question, ‘Can we use any reference electrode irrespective of its pH-compatibility?’.

    DOI

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    10
    Citation
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  • Controlled Nitrogen Doping in Crumpled Graphene for Improved Alkali Metal‐Ion Storage under Low‐Temperature Conditions

    Kyungbin Lee, Michael J. Lee, Jeonghoon Lim, Kun Ryu, Mochen Li, Suguru Noda, Seok Joon Kwon, Seung Woo Lee

    Advanced Functional Materials   33 ( 2 ) 2209775 - 2209775  2022.10  [Refereed]

    DOI

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    13
    Citation
    (Scopus)
  • How properly are we interpreting the Tafel lines in energy conversion electrocatalysis?

    Sengeni Anantharaj, Suguru Noda

    Materials Today Energy   29   101123 - 101123  2022.10  [Refereed]

    Authorship:Last author

    DOI

    Scopus

    53
    Citation
    (Scopus)
  • (Invited) Production and Functionalization of Carbon Nanotubes for Electrochemical Energy Storage Devices

    Suguru Noda

    ECS Meeting Abstracts    2022.07

    DOI

  • Systematic investigation of anode catalysts for liquid ammonia electrolysis

    Natsuho Akagi, Keisuke Hori, Hisashi Sugime, Suguru Noda, Nobuko Hanada

    Journal of Catalysis   406   222 - 230  2022.02

     View Summary

    Liquid ammonia is able to release hydrogen via electrolysis with a theoretical voltage of 0.077 V. However, the actual operation voltage is much higher (around 1–2 V) due to the large overpotential of the anodic reaction. We systematically investigated Pt, Ir, Ru, Ni, Co, Fe, Ta, and Ti as the anodic catalyst, and observed a volcano correlation when plotting the current density against the formation enthalpy of metal nitrides per nitrogen ΔfHMN (kJ/mol-N). ΔfHMN reflects the strength of metal-nitrogen bond, and Ru having a moderate ΔfHMN showed the highest catalytic activity. Then, the activity enhancement via microstructure control was examined. The sputtered Pt and Ni films having a columnar structure with a rough surface showed 7- and 13-times higher current density than the Pt and Ni plates, respectively. An anodic current density of 0.45 mA/cm2 was achieved for the sputtered Ni film at an anodic potential as low as 0.3 V vs H2/NH3.

    DOI

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    4
    Citation
    (Scopus)
  • Fast and stable hydrogen storage in the porous composite of MgH2 with Nb2O5 catalyst and carbon nanotube

    Kosuke Kajiwara, Hisashi Sugime, Suguru Noda, Nobuko Hanada

    Journal of Alloys and Compounds   893   162206 - 162206  2022.02  [Refereed]

     View Summary

    The MgH2-Nb2O5-carbon nanotube (CNT) composite was fabricated to accommodate the volume change of particles during the hydrogen storage cycles by holding the MgH2-Nb2O5 particles within the sponge-like matrix of the CNT. This allowed for preservation of the composite structure and led to more stable hydrogen sorption properties during 20 cycles, as compared to without CNT. To investigate this effect of CNT on the cyclic stability of MgH2-Nb2O5, CNT and expanded graphite (EG) were added to MgH2-Nb2O5 via ball milling. The MgH2-Nb2O5-CNT powder showed stable cyclic performance, similar to the MgH2-Nb2O5-CNT composite, whereas the MgH2-Nb2O5-EG powder exhibited cyclic degradation similar to MgH2-Nb2O5. From SEM-EDS, it was found that the C/Mg ratio of the surface of the MgH2-Nb2O5-CNT powder was higher than that of the MgH2-Nb2O5-EG powder. Thus, the fibrous CNT on the surface of the MgH2 particles could be responsible for the greater cyclic stability of the MgH2-Nb2O5-CNT composite.

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    36
    Citation
    (Scopus)
  • Ag Nanoparticle-Based Aerogel-like Films for Interfacial Thermal Management

    Sebun Munakata, Shunji Kobayashi, Hisashi Sugime, Shota Konishi, Junichiro Shiomi, Suguru Noda

    ACS Applied Nano Materials    2022

     View Summary

    A Ag aerogel-like film (referred to as aerogel hereafter), used as a thermal interface material with enhanced performance and thermal stability, is reported. An aerogel/foil/aerogel "monocomposite"is created by rapidly forming and depositing Ag nanoparticles on both faces of a Ag foil by the gas-evaporation and particle-deposition method in a few minutes. The monocomposite, having an aerogel of a low packing ratio (<10%) with a clean surface, exhibits low thermal resistance (18 mm2 K W-1) when sandwiched with Cu rods. The monocomposite exhibits excellent thermal stability and significantly reduced thermal resistance (3.0 mm2 K W-1) at 246 °C, keeping its low thermal resistance (2.8 mm2 K W-1) after the temperature is decreased to 51 °C; further, the resistance reduces to 2.1 mm2 K W-1 after 10 cycles of heating and cooling (100-200 °C). The Ag monocomposite, having high performance comparable to that of the benchmark In sheet and excellent thermal stability at a temperature higher than the melting point of In, will enable high-power and high-temperature operation of computing and power devices.

    DOI

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    1
    Citation
    (Scopus)
  • Dos and don’ts in screening water splitting electrocatalysts

    Sengeni Anantharaj, Suguru Noda

    Energy Advances    2022

     View Summary

    A perspective with an explicit account of the appropriate screening of water splitting electrocatalysts advocating dos and don’ts!

    DOI

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    26
    Citation
    (Scopus)
  • Layered 2D transition metal (W, Mo, and Pt) chalcogenides for hydrogen evolution reaction

    Sengeni Anantharaj, Suguru Noda

    Sulfide and Selenide Based Materials for Emerging Applications     495 - 525  2022

    DOI

  • Worrisome Exaggeration of Activity of Electrocatalysts Destined for Steady-State Water Electrolysis by Polarization Curves from Transient Techniques

    Sengeni Anantharaj, Subrata Kundu, Suguru Noda

    Journal of The Electrochemical Society   169 ( 1 ) 014508 - 014508  2022.01

     View Summary

    Cyclic and linear sweep voltammetry techniques substantially misjudge the performance of water splitting electrocatalysts due to their transient nature that forbids the interface from reaching a steady-state. This misjudgment leads to the potentially detrimental yet unwittingly falsified data accumulation in the literature that requires immediate attention. Alternatively, sampled-current voltammetry (SCV) constructed from steady-state responses is advised to be widely adopted for screening electrocatalysts that are actually destined for steady-state operations. To show that this exaggeration is universal, a well-characterized activated SS, coprecipitated Co(OH)2, and Pt foil electrodes are studied for OER and HER in 1.0 M KOH. The results urge that it is time to adopt a relatively more precise alternative technique such as SCV.

    DOI

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    39
    Citation
    (Scopus)
  • iR drop correction in electrocatalysis: everything one needs to know!

    Sengeni Anantharaj, Suguru Noda

    Journal of Materials Chemistry A   10 ( 17 ) 9348 - 9354  2022

     View Summary

    This perspective details every single aspects of iRu drop correction in controlled-potential electrocatalysis from fundamentals to the best practices.

    DOI

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    51
    Citation
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  • Layered 2D PtX2 (X = S, Se, Te) for the electrocatalytic HER in comparison with Mo/WX2 and Pt/C: are we missing the bigger picture?

    Sengeni Anantharaj, Suguru Noda

    Energy &amp; Environmental Science   15 ( 4 ) 1461 - 1478  2022

     View Summary

    A critical perspective that questions the use of PtX2 for the HER when we have a better performing Pt/C while analysing the potential ways in which PtX2 can actually be better than Pt/C.

    DOI

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    40
    Citation
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  • Efficient Methanol Electrooxidation Catalyzed by Potentiostatically Grown Cu–O/OH(Ni) Nanowires: Role of Inherent Ni Impurity

    Sengeni Anantharaj, Taiki Nagamatsu, Shohei Yamaoka, Mochen Li, Suguru Noda

    ACS Applied Energy Materials    2021.12

    DOI

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    11
    Citation
    (Scopus)
  • Why shouldn’t double-layer capacitance (Cdl) be always trusted to justify Faradaic electrocatalytic activity differences?

    Sengeni Anantharaj, Hisashi Sugime, Suguru Noda

    Journal of Electroanalytical Chemistry   903   115842 - 115842  2021.12

    DOI

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    51
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  • Controllable pore structures of pure and sub-millimeter-long carbon nanotubes

    Dong Young Kim, Ji Hoon Kim, Mochen Li, Suguru Noda, Jungpil Kim, Kwang-Seok Kim, Keun Soo Kim, Cheol-Min Yang

    Applied Surface Science   566   150751 - 150751  2021.11  [Refereed]

    DOI

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    10
    Citation
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  • The Significance of Properly Reporting Turnover Frequency in Electrocatalysis Research

    Sengeni Anantharaj, Pitchiah Esakki Karthik, Suguru Noda

    Angewandte Chemie International Edition    2021.09  [Refereed]

    Authorship:Last author

    DOI

    Scopus

    193
    Citation
    (Scopus)
  • Enhanced CO2-assisted growth of single-wall carbon nanotube arrays using Fe/AlO catalyst annealed without CO2

    Mochen Li, Kotaro Yasui, Hisashi Sugime, Suguru Noda

    Carbon   185   264 - 271  2021.09  [Refereed]

    Authorship:Last author, Corresponding author

     View Summary

    Controlling catalyst-particle formation is essential for the growth of single-wall carbon nanotube (SWCNT) arrays with improved alignment, areal mass, and height. We have previously reported the positive effect of CO2 on SWCNT growth via chemical vapor deposition, and in this study, we found its negative effect on catalyst-particle formation during annealing. A Fe (1 nm)/AlOx (15 nm) catalyst that was sputter-deposited on SiO2/Si substrates demonstrated a prolonged lifetime and enabled the growth of SWCNT arrays with better alignment, twice the height, and three times higher areal mass when the catalyst was annealed under 10 vol% H2/Ar without CO2 than with 1 vol% CO2. Detailed analysis indicated that the Fe particles could remain partially oxidized during annealing in H2 with mildly oxidative CO2, resulting in the bulk diffusion of Fe into the AlOx layer. In contrast, Fe is reduced sufficiently in H2 in the absence of CO2, thereby remaining on the AlOx surface and active for SWCNT growth. The findings of this study emphasize the importance of maintaining a highly reductive atmosphere during annealing to achieve active catalyst particles with a higher number density and longer lifetime.

    DOI

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    7
    Citation
    (Scopus)
  • High-energy-density Li–S battery with positive electrode of lithium polysulfides held by carbon nanotube sponge

    Yuichi Yoshie, Keisuke Hori, Tomotaro Mae, Suguru Noda

    Carbon   182   32 - 41  2021.09  [Refereed]

    Authorship:Last author, Corresponding author

    DOI

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    19
    Citation
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  • Carbon nanotube/silicon heterojunction solar cell with an active area of 4 cm2 realized using a multifunctional molybdenum oxide layer

    Xiaoxu Huang, Emina Hara, Hisashi Sugime, Suguru Noda

    Carbon    2021.08  [Refereed]

    Authorship:Last author, Corresponding author

    DOI

    Scopus

    8
    Citation
    (Scopus)
  • Thermal properties of single-walled carbon nanotube forests with various volume fractions

    JinHyeok Cha, Kei Hasegawa, Jeonyoon Lee, Itai Y. Stein, Asuka Miura, Suguru Noda, Junichiro Shiomi, Shohei Chiashi, Brian L. Wardle, Shigeo Maruyama

    International Journal of Heat and Mass Transfer   171   121076 - 121076  2021.06  [Refereed]

     View Summary

    Needs of a material for thermal management in reduced-sized electronic devices drive single-walled carbon nanotubes (SWCNTs) to be one of the most promising candidates due to their excellent thermal properties. Many numerical and experimental studies have reported on understanding thermal properties of the SWCNT for thermal device applications. In the present study, thermal diffusivity and conductivity of SWCNT forests in the axial direction with various volume fractions of SWCNTs were measured by laser flash analysis technique and the same properties of an individual SWCNT were derived. The volume fraction was controlled up to 25 vol% by biaxial mechanical densification which maintains SWCNT alignment. While the thermal diffusivity of SWCNT forests was almost constant, it increased when the volume fraction was higher than 17 vol%, suggesting that some SWCNTs, which did not serve as a thermal path in the case of lower volume fraction, were connected with the other SWCNTs. Through the increase of inferred thermal conductivity equivalent to an individual SWCNT after 17 vol%, we also realized that the enhancement of volume fraction of SWCNT forest diminished thermal boundary resistance in good agreement with the tendency inferred from the reported numerical data. (C) 2021 Elsevier Ltd. All rights reserved.

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    8
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  • Fluidized-bed production of 0.3 mm-long single-wall carbon nanotubes at 28% carbon yield with 0.1 mass% catalyst impurities using ethylene and carbon dioxide

    Mochen Li, Soichiro Hachiya, Zhongming Chen, Toshio Osawa, Hisashi Sugime, Suguru Noda

    Carbon   182   23 - 31  2021.05  [Refereed]

    Authorship:Last author, Corresponding author

    DOI

    Scopus

    8
    Citation
    (Scopus)
  • Numerical simulation of heat supply and hydrogen desorptionby hydrogen flow to porous MgH2 sheet

    Keisuke Yoshida, Kosuke Kajiwara, Hisashi Sugime, Suguru Noda, Nobuko Hanada

    Chemical Engineering Journal   421   129648 - 129648  2021.04  [Refereed]

    Authorship:Corresponding author

     View Summary

    We propose using hydrogen as a heat transfer medium to supply waste heat from hydrogen-driven devices to hydrogen storage tanks. In our model, MgH is used in the form of porous sheets, set in parallel in the tank, and heat is supplied via hot hydrogen flowed through the interspaces between the porous sheets. Feasibility of the hydrogen desorption reaction in this process was verified numerically. Hydrogen efficiently carried heat to the stack of porous MgH sheets via convective heat transfer and then carried heat into the porous MgH sheets via conductive heat transfer through the pores owing to its high thermal conductivity. We found that the hydrogen desorption is also fast enough to allow the supplied heat to be used efficiently to drive the endothermic hydrogen desorption reaction. It was understood that the thickness of the MgH sheet and hot hydrogen flow speed affected hydrogen desorption. These factors can be evaluated by using the dimensionless number of τ /τ which is the ratio of the space time to the time constant for heat transfer in the MgH sheet. Under τ /τ > 0.01 range, both the reaction and heat transfer are fast enough, the hydrogen desorption is limited by heat supply, and hydrogen desorption amount is proportional to the heat supplied to the reactor. The tank structure and operating conditions can be designed by using the dimensionless number of τ /τ . 2 2 2 2 s h 2 s h s h

    DOI

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    5
    Citation
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  • The Pitfalls of Using Potentiodynamic Polarization Curves for Tafel Analysis in Electrocatalytic Water Splitting

    Sengeni Anantharaj, Suguru Noda, Matthias Driess, Prashanth W. Menezes

    ACS Energy Letters   6   1607 - 1611  2021.03  [Refereed]

    Authorship:Corresponding author

    DOI

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    271
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  • Two‐Dimensional Polydopamine Positive Electrodes for High‐Capacity Alkali Metal‐Ion Storage

    Byeongyong Lee, Kyungbin Lee, Mochen Li, Suguru Noda, Seung Woo Lee

    ChemElectroChem   8 ( 6 ) 1070 - 1077  2021.02  [Refereed]

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    3
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  • Ultra-long carbon nanotube forest via in situ supplements of iron and aluminum vapor sources

    Hisashi Sugime, Toshihiro Sato, Rei Nakagawa, Tatsuhiro Hayashi, Yoku Inoue, Suguru Noda

    Carbon   172   772 - 780  2021.02  [Refereed]

    Authorship:Last author

     View Summary

    © 2020 Elsevier Ltd A carbon nanotube forest with a length of 14 cm grew with an average growth rate of 1.5 μm s−1 and a growth lifetime of 26 h. Several key factors to realize this unprecedented long growth such as catalyst conditions, growth conditions in chemical vapor deposition, and reactor system were clarified. It was found that the combination of the catalyst system of iron/gadolinium/aluminum oxide (Fe/Gd/Al2Ox) and the in situ supplements of Fe and Al vapor sources at very low concentration was crucially important. A cold-gas system, where only the substrate is heated while keeping the gas at room temperature, was employed to suppress unnecessary reactions and depositions. The long carbon nanotube forest enabled macroscopic measurements of the tensile and electrical properties of the carbon nanotube wires, and it gave several important insights for industrial applications of the carbon nanotubes in the future.

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    36
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  • “The Fe Effect”: A review unveiling the critical roles of Fe in enhancing OER activity of Ni and Co based catalysts

    Sengeni Anantharaj, Subrata Kundu, Suguru Noda

    Nano Energy   80   105514 - 105514  2021.02  [Refereed]

    Authorship:Last author, Corresponding author

     View Summary

    Electrocatalytic oxygen evolution reaction (OER) catalyzed by non-precious metals and their compounds in alkaline medium is an attractive area of energy research for the generation of hydrogen from water. The 3d transition metals, particularly, Ni and Co show better OER activity than others in alkaline medium. Ni and Co based oxygen-evolving catalysts (OECs) experience an enormous enhancement in the OER activity either by incidental or intentional Fe doping/incorporation. To account for this, different roles of Fe that it exerts when incorporated into these OECs are reported to be responsible. Unfortunately, the conclusions drawn in many related studies are often contradictory to one another. Important contradictory conclusions are: 1) a few studies claim Fe is the active site and Ni/Co are inactive while other studies claim Ni/Co and Fe act together in OER, 2) a few studies claim Fe stays unoxidized while a few shows evidence for the existence of Fe , and 3) a few studies suggest Fe is the faster site in Ni/Co OEC matrices for OER but fail to explain similar effects observed with other OER matrices. Many critical experimental and theoretical investigations have been made recently to reveal this magical Fe effect and the results of those studies are coherently presented here with critical discussion. This review is presented as it is inevitable to know the critical roles of Fe effect in Ni/Co based OECs to succeed in energy efficient hydrogen generation in alkaline medium. 3+ 4+ 3+

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  • Outstanding Low‐Temperature Performance of Structure‐Controlled Graphene Anode Based on Surface‐Controlled Charge Storage Mechanism

    Michael J. Lee, Kyungbin Lee, Jeonghoon Lim, Mochen Li, Suguru Noda, Seok Joon Kwon, Brianne DeMattia, Byeongyong Lee, Seung Woo Lee

    Advanced Functional Materials   31 ( 14 ) 2009397 - 2009397  2021.01  [Refereed]

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    41
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  • Strategies and Perspectives to Catch the Missing Pieces in Energy‐Efficient Hydrogen Evolution Reaction in Alkaline Media

    Sengeni Anantharaj, Suguru Noda, Vasanth Rajendhiran Jothi, Sung Chul Yi, Matthias Driess, Prashanth W. Menezes

    Angewandte Chemie International Edition    2021.01  [Refereed]

    Authorship:Corresponding author

     View Summary

    Transition metal hydroxides (M-OH) and their heterostructures (X|M-OH, where X can be a metal, metal oxide, metal chalcogenide, metal phosphide, etc.) have recently emerged as highly active electrocatalysts for hydrogen evolution reaction (HER) of alkaline water electrolysis. Lattice hydroxide anions in metal hydroxides are primarily responsible for observing such an enhanced HER activity in alkali that facilitate water dissociation and assist the first step, the hydrogen adsorption. Unfortunately, their poor electronic conductivity had been an issue of concern that significantly lowered its activity. Interesting advancements were made when heterostructured hydroxide materials with a metallic and or a semiconducting phase were found to overcome this pitfall. However, in the midst of recently evolving metal chalcogenide and phosphide based HER catalysts, significant developments made in the field of metal hydroxides and their heterostructures catalysed alkaline HER and their superiority have unfortunately been given negligible attention. This review, unlike others, begins with the question of why alkaline HER is difficult and will take the reader through evaluation perspectives, trends in metals hydroxides and their heterostructures catalysed HER, an understanding of how alkaline HER works on different interfaces, what must be the research directions of this field in near future, and eventually summarizes why metal hydroxides and their heterostructures are inevitable for energy-efficient alkaline HER.

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  • Pushing the Limits of Rapid Anodic Growth of CuO/Cu(OH)2 Nanoneedles on Cu for the Methanol Oxidation Reaction: Anodization pH Is the Game Changer

    Sengeni Anantharaj, Hisashi Sugime, Shohei Yamaoka, Suguru Noda

    ACS Applied Energy Materials   4 ( 1 ) 899 - 912  2021.01  [Refereed]

    Authorship:Last author, Corresponding author

     View Summary

    We recently reported the fastest anodization method (just 80 s) of all for accessing a denser array of Cu(OH)2-CuO nanoneedles on a Cu foil substrate by applying a constant potential of 0.864 V vs a reversible hydrogen electrode in 1.0 M KOH that delivered a better activity for the methanol oxidation reaction (MOR). In this study, we show that the strength of the KOH solution used for anodization alters the size, morphology, surface chemistry, electrochemical accessibility of Cu sites, and the subsequent MOR activity trend. Intriguingly, an increase in KOH solution strength shortens the time of anodization from 80 s (1.0 M KOH) to 20 s with 3.0 M KOH, which in turn drastically reduces to just 6 s with 6.0 M KOH. As of now, this is the shortest time ever achieved for the anodic growth of Cu-OH/O nanoneedles on a Cu substrate. A set of detailed and comparative physical and electrochemical characterizations reveal positive relationships between anodization pH and anodization current, the size of Cu-OH/O nanoneedles grown, rate of growth, electrochemical accessibility of Cu sites, and electrocatalytic MOR activity. Thus, this study provides a universal approach to control the size of Cu-OH/O nanoneedles, electrochemical accessibility of Cu sites, and their subsequent MOR activity.

    DOI

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    26
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  • High-performance solution-based silicon heterojunction solar cells using carbon nanotube with polymeric acid doping

    Rongbin Xie, Hisashi Sugime, Suguru Noda

    Carbon   175   519 - 524  2021.01  [Refereed]

    Authorship:Last author, Corresponding author

     View Summary

    Carbon nanotube (CNT)/n-Si heterojunction solar cells were fabricated based on solution processes. CNT film with high transparency of 90% and low sheet resistance of ∼115 Ω/sq was fabricated from commercially available CNT powder via dispersion-filtration process using poly(p-styrene-sulfonic acid) (PSS) as both dispersant and dopant. Heterojunction was then fabricated by attaching the CNT-PSS film onto an n-Si wafer. The CNT/n-Si solar cell showed an enhanced efficiency of 11.7% with the PSS-doping compared with the device without doping (7.7%). The device showed further improvements in efficiency to 14.1% with an antireflective coating layer of sulfonated polytetrafluoroethylene (Nafion) and stability to 1000 h in ambient air without additional protection. The solution-based strategies using polymeric acids for efficiency and stability enhancement will open new avenues for the low-cost CNT/Si heterojunction solar cells.

    DOI

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    8
    Citation
    (Scopus)
  • Performance enhancement of carbon nanotube/silicon solar cell by solution processable MoO

    Xiaoxu Huang, Rongbin Xie, Hisashi Sugime, Suguru Noda

    Applied Surface Science   542   148682 - 148682  2020.12  [Refereed]

    Authorship:Last author, Corresponding author

     View Summary

    © 2020 Elsevier B.V. Carbon nanotube/silicon solar cells have increasingly attracted attention owing to their high efficiency and cost-effectiveness. Herein, we demonstrated a significant improvement in the performance of the carbon nanotube/silicon solar cell by applying solution-processable MoOx. The MoOx acts as both an efficient chemical dopant and an anti-reflection coating, resulting in a reduction in the series resistance and an enhancement of the short-circuit current density of the cell. As a result, the power conversion efficiencies increased to 10.0%, which is a 39% increase from the pristine value (7.2%). The device showed considerable stability, maintaining the power conversion efficiency at 80% of its original value for two months in the air without any protective layer. The simple solution process at room-temperature in this study can lower the preparation cost and pave a way for the practical application of carbon nanotube/silicon solar cells.

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    13
    Citation
    (Scopus)
  • A review on recent developments in electrochemical hydrogen peroxide synthesis with a critical assessment of perspectives and strategies

    Sengeni Anantharaj, Sudhagar Pitchaimuthu, Suguru Noda

    Advances in Colloid and Interface Science   287   102331 - 102331  2020.12  [Refereed]

    Authorship:Last author, Corresponding author

     View Summary

    Electrochemical hydrogen peroxide synthesis using two-electron oxygen electrochemistry is an intriguing alternative to currently dominating environmentally unfriendly and potentially hazardous anthraquinone process and noble metals catalysed direct synthesis. Electrocatalytic two-electron oxygen reduction reaction (ORR) and water oxidation reaction (WOR) are the source of electrochemical hydrogen peroxide generation. Various electrocatalysts have been used for the same and were characterized using several electroanalytical, chemical, spectroscopic and chromatographic tools. Though there have been a few reviews summarizing the recent developments in this field, none of them have unified the approaches in catalysts' design, criticized the ambiguities and flaws in the methods of evaluation, and emphasized the role of electrolyte engineering. Hence, we dedicated this review to discuss the recent trends in the catalysts' design, performance optimization, evaluation perspectives and their appropriateness and opportunities with electrolyte engineering. In addition, particularized discussions on fundamental oxygen electrochemistry, additional methods for precise screening, and the role of solution chemistry of synthesized hydrogen peroxide are also presented. Thus, this review discloses the state-of-the-art in an unpresented view highlighting the challenges, opportunities, and alternative perspectives.

    DOI PubMed

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    54
    Citation
    (Scopus)
  • Chemical Leaching of Inactive Cr and Subsequent Electrochemical Resurfacing of Catalytically Active Sites in Stainless Steel for High-Rate Alkaline Hydrogen Evolution Reaction

    Sengeni Anantharaj, Hisashi Sugime, Suguru Noda

    ACS Applied Energy Materials   3 ( 12 ) 12596 - 12606  2020.11  [Refereed]

    Authorship:Last author, Corresponding author

     View Summary

    In this study, we show a simple two-step surface engineering method that uses chemical oxidation (using KOH and NaClO in 1:2 M ratio)-assisted leaching of metals (Cr, Mn, and Ni) from the surface and an electrochemical potentiostatic activation enabled resurfacing of only catalytically active Ni and Mn of the alloy. Such surface-engineered stainless steel 304 (SS-304-Ox-ECA) foils rich in Ni(OH)2 and multivalent Mn oxides were found to have a coarse texture with uniform nanostructures. As a result of leached Cr, resurfaced catalytically active sites improved roughness with nanotexturing and enhanced the charge-transfer ability. The SS-304-Ox-ECA foil has become a high-performance HER electrocatalyst that delivered 400 mA cm-2 higher current density at -0.8 V versus RHE and demanded 210 mV lower overpotential for a current density of 100 mA cm-2 than pristine SS-304 foils in 1.0 M KOH. A smaller Tafel slope (90 mV dec-1) and a higher double-layer capacitance (2Cdl = 0.784 μF cm-2) further justified that the activity enhancement is also due to the improved HER kinetics and increased electrochemical surface area. This catalytic electrode of high abundance and low cost is a promising candidate for cost-efficient hydrogen production from water.

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    20
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    (Scopus)
  • Surface amorphized nickel hydroxy sulphide for efficient hydrogen evolution reaction in alkaline medium

    Sengeni Anantharaj, Hisashi Sugime, Suguru Noda

    Chemical Engineering Journal   408   127275 - 127275  2020.10  [Refereed]

    Authorship:Last author, Corresponding author

     View Summary

    Non-oxide/hydroxide hydrogen evolution reaction (HER) catalysts undergo hydroxylation to a significant extent even under reductive condition when exposed to alkali. Actual role of such hydroxylation in alkaline HER electrocatalysis is not previously given any significance. In this study, we report an intriguing finding that nickel sulfide a well-known HER electrocatalyst when subjected to anodic potential cycling covering Ni and Ni redox couple led to accelerated hydroxylation accompanying surface amorphization. As a result, improved electrochemical surface, better HER kinetics, and better charge transfer were achieved that lowering the HER overpotential by 110 mV at 100 mA cm . This surface amorphized and hydroxylated nickel sulfide exhibited excellent stability upon both galvanostatic and potentiostatic electrolysis for over 50 h. Besides, it also showed a lower Tafel slope (120 mV dec ), higher relative ECSA in terms of 2C (3.85 µF cm ), and higher electrochemical accessibility for Ni sites (3.7 × 10 cm ) which further advocate the superiority of our way of improving HER activity of a non-oxide/hydroxide catalyst. Thus, this study open up new avenues for re-examining other non-oxide/hydroxide catalysts in alkaline HER for benefiting the energy and cost-efficient hydrogen generation. 2+ 3+ 2 -1 −2 17 −2 dl

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    65
    Citation
    (Scopus)
  • Boosting the Oxygen Evolution Activity of Copper Foam Containing Trace Ni by Intentionally Supplementing Fe and Forming Nanowires in Anodization

    Sengeni Anantharaj, Hisashi Sugime, Bozhi Chen, Natsuho Akagi, Suguru Noda

    Electrochimica Acta   364   137170 - 137170  2020.10  [Refereed]

    Authorship:Last author, Corresponding author

     View Summary

    Oxygen evolution reaction (OER) is the bottleneck for realizing energy-efficient hydrogen production through water electrolysis in both acid and alkali. Alkaline OER electrocatalyzed by Ni and Co hydroxides are well known which showed unexpected enhancement with the addition of Fe. We found that the commercially procured Cu foam containing trace amount of Ni (~1.5 wt.%) upon anodization formed Cu(OH) –CuO nanowires with conceivable formation of Ni(OH) and experienced a notable enhancement in its OER activity. When sufficient amount of Fe was intentionally supplemented during anodization, OER activity of the same was further improved. Specifically, as a combined result of anodization in KOH and in Fe supplemented KOH, overpotential at 50 mA cm was lowered by 153 mV. Such an activation also improved the kinetics of OER by lowering the Tafel slope by 100 mV dec . With these, it has been shown here that a moderately active OER catalyst i.e., Cu(OH) –CuO/Cu formed upon the anodization of Cu foam can be turned into a highly active catalyst just by utilizing the trace Ni that it already contains and intentionally supplementing sufficient amount of Fe. 2 2 2 −2 −1

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    17
    Citation
    (Scopus)
  • Nanotubes make battery lighter and safer

    Kaneko, K., Hori, K., Noda, S.

    Carbon   167   596 - 600  2020.10  [Refereed]

    Authorship:Last author, Corresponding author

    DOI

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    7
    Citation
    (Scopus)
  • Dispersing and doping carbon nanotubes by poly(p-styrene-sulfonic acid) for high-performance and stable transparent conductive films

    Rongbin Xie, Hisashi Sugime, Suguru Noda

    Carbon   164   150 - 156  2020.08  [Refereed]

    Authorship:Last author, Corresponding author

    DOI

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    21
    Citation
    (Scopus)
  • Ultrafast Growth of a Cu(OH)2–CuO Nanoneedle Array on Cu Foil for Methanol Oxidation Electrocatalysis

    Sengeni Anantharaj, Hisashi Sugime, Suguru Noda

    ACS Applied Materials & Interfaces   12 ( 24 ) 27327 - 27338  2020.06  [Refereed]

    Authorship:Last author, Corresponding author

     View Summary

    A swift potentiostatic anodization method for growing a 5-7 μm tall nanoneedle array of Cu(OH)2-CuO on Cu foil within 100 s has been developed. This catalytic electrode when screened for methanol oxidation electrocatalysis in 1 M KOH with 0.5 M methanol, delivered a current density as high as 70 ± 10 mA cm-2 at 0.65 V versus Hg/HgO which is superior to the performance of many related catalysts reported earlier. The observed activity enhancement is attributed to the formation of both Cu(OH)2-CuO nanoneedle arrays of high active surface area over the metallic Cu foil. In addition, the Cu(OH)2-CuO/Cu electrode had also exhibited excellent stability upon prolonged potentiostatic electrocatalytic oxidation of methanol while retaining the charge-transfer characteristics. Growth of such highly ordered assembly of Cu(OH)2-CuO nanoneedles within a minute has never been achieved before. When compared to its oxygen evolution reaction activity, the addition of 0.5 M methanol has lowered the overpotential at 10 mA cm-2 by 334 mV, which is significant. This encourages the use of methanol as a sacrificial anolyte for energy-saving production of H2 from water electrolysis.

    DOI PubMed

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    98
    Citation
    (Scopus)
  • Facile catalyst deposition using mist for fluidized-bed production of sub-millimeter-long carbon nanotubes

    Mochen Li, Maeda Risa, Toshio Osawa, Hisashi Sugime, Suguru Noda

    Carbon   167   256 - 263  2020.06  [Refereed]

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    12
    Citation
    (Scopus)
  • All-Soft Supercapacitors Based on Liquid Metal Electrodes with Integrated Functionalized Carbon Nanotubes

    Min-gu Kim, Byeongyong Lee, Mochen Li, Suguru Noda, Choongsoon Kim, Jayoung Kim, Woo-Jin Song, Seung Woo Lee, Oliver Brand

    ACS Nano   14 ( 5 ) 5659 - 5667  2020.05  [Refereed]

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    58
    Citation
    (Scopus)
  • Appropriate Use of Electrochemical Impedance Spectroscopy in Water Splitting Electrocatalysis

    Sengeni Anantharaj, Suguru Noda

    ChemElectroChem   7 ( 10 ) 2297 - 2308  2020.05  [Refereed]

    Authorship:Last author

    DOI

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    161
    Citation
    (Scopus)
  • Achieving Increased Electrochemical Accessibility and Lowered Oxygen Evolution Reaction Activation Energy for Co2+ Sites with a Simple Anion Preoxidation

    Sengeni Anantharaj, Hisashi Sugime, Bozhi Chen, Natsuho Akagi, Suguru Noda

    The Journal of Physical Chemistry C   124 ( 18 ) 9673 - 9684  2020.05  [Refereed]

    Authorship:Last author, Corresponding author

    DOI

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    34
    Citation
    (Scopus)
  • Nickel selenides as pre-catalysts for electrochemical oxygen evolution reaction: A review

    Sengeni Anantharaj, Suguru Noda

    International Journal of Hydrogen Energy    2020.05  [Refereed]

    Authorship:Last author, Corresponding author

    DOI

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    121
    Citation
    (Scopus)
  • Enhanced Lithium Storage of an Organic Cathode via the Bipolar Mechanism

    Tianyuan Liu, Ki Chul Kim, Byeongyong Lee, Shikai Jin, Michael J. Lee, Mochen Li, Suguru Noda, Seung Soon Jang, Seung Woo Lee

    ACS Applied Energy Materials   3 ( 4 ) 3728 - 3735  2020.04  [Refereed]

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    17
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  • Life Cycle Greenhouse Gas Emissions of Long and Pure Carbon Nanotubes Synthesized via On-Substrate and Fluidized-Bed Chemical Vapor Deposition

    Heng Yi Teah, Toshihiro Sato, Katsuya Namiki, Mayu Asaka, Kaisheng Feng, Suguru Noda

    ACS Sustainable Chemistry &amp; Engineering   8 ( 4 ) 1730 - 1740  2020.01  [Refereed]

    Authorship:Last author, Corresponding author

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    24
    Citation
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  • Electrolysis of ammonia in aqueous solution by platinum nanoparticles supported on carbon nanotube film electrode

    N. Hanada, Y. Kohase, K. Hori, H. Sugime, S. Noda

    Electrochimica Acta   341   136027 - 136027  2020  [Refereed]

    Authorship:Last author

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    28
    Citation
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  • Progress in nickel chalcogenides electrocatalyzed hydrogen evolution reaction

    Sengeni Anantharaj, Subrata Kundu, Suguru Noda

    Journal of Materials Chemistry A   8 ( 8 ) 4174 - 4192  2020  [Refereed]

    Authorship:Last author, Corresponding author

     View Summary

    Electrochemical water splitting powered by electrical energy derived from renewable sources is a green and faster way of producing bulk hydrogen with the highest purity. Unfortunately, the cost-inefficiency associated with energy loss (as overpotential) and costs of electrode materials have been forbidding this technology to surpass the currently dominant industrial process (steam reforming of hydrocarbons). With the recent evolution of transition metal chalcogenides, efficient commercial electrochemical water splitting is not too far. Transition metal chalcogenides are better in the hydrogen evolution reaction (HER) than pristine metals as they have negatively polarized chalcogenide anions with relatively lower free energy for proton adsorption. Moreover, chalcogenides are relatively easy to prepare and handle. Several metal chalcogenides have been reported with good HER activity among which Ni chalcogenides are reported to be exceptional ones. In recent years, growth of the nickel chalcogenide catalysed HER is massive. This review is devoted to bringing out a comprehensive understanding of what had happened in the recent past of this field with highlights on future prospects. In addition, we have also briefed the key physico-chemical properties of these materials and highlighted what one should anticipate while screening an electrocatalyst for electrochemical water splitting.

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    190
    Citation
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  • High-energy density Li<inf>x</inf>Si-S full cell based on 3D current collector of few-wall carbon nanotube sponge

    Hori, K., Yamada, Y., Momma, T., Noda, S.

    Carbon   161   612 - 621  2020  [Refereed]

    Authorship:Last author, Corresponding author

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    10
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  • Amorphous catalysts and electrochemical water splitting: An untold story of harmony

    S. Anantharaj, S. Noda

    Small   16 ( 2 ) 1905779  2020  [Refereed]

    Authorship:Last author, Corresponding author

     View Summary

    In the near future, sustainable energy conversion and storage will largely depend on the electrochemical splitting of water into hydrogen and oxygen. Perceiving this, countless research works focussing on the fundamentals of electrocatalysis of water splitting and on performance improvements are being reported everyday around the globe. Electrocatalysts of high activity, selectivity, and stability are anticipated as they directly determine energy- and cost efficiency of water electrolyzers. Amorphous electrocatalysts with several advantages over crystalline counterparts are found to perform better in electrocatalytic water splitting. There are plenty of studies witnessing performance enhancements in electrocatalysis of water splitting while employing amorphous materials as catalysts. The harmony between the flexibility of amorphous electrocatalysts and electrocatalysis of water splitting (both the oxygen evolution reaction [OER] and the hydrogen evolution reaction [HER]) is one of the untold and unsummarized stories in the field of electrocatalytic water splitting. This Review is devoted to comprehensively discussing the upsurge of amorphous electrocatalysts in electrochemical water splitting. In addition to that, the basics of electrocatalysis of water splitting are also elaborately introduced and the characteristics of a good electrocatalyst for OER and HER are discussed.

    DOI PubMed

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    428
    Citation
    (Scopus)
  • Gd-enhanced growth of multi-millimeter-tall forests of single-wall carbon nanotubes

    H. Sugime, T. Sato, R. Nakagawa, C. Cepek, S. Noda

    ACS Nano   13 ( 11 ) 13208 - 13216  2019.11  [Refereed]

     View Summary

    © 2019 American Chemical Society. Multi-millimeter-tall vertically aligned single-wall carbon nanotube (VA-SWCNT) forests were grown using Fe/Gd/Al2Ox catalyst with high initial growth rate of ∼2 μm s-1 and long catalyst lifetime of ∼70 min at 800 °C. The addition of Gd with a nominal thickness of 0.3 nm drastically prolonged the catalyst lifetime. The analysis of the VA-SWCNT forests by a transmission electron microscope showed that the average diameter of the SWCNTs grown with Gd is constant from the top to the bottom of the forests, while it monotonically increased without Gd. This indicated that Gd suppresses the structure change of the Fe nanoparticles in the lateral direction during the CNT growth. By X-ray photoelectron spectroscopy, it was found that the longer catalyst lifetime with Gd stems from the suppression of the interaction between Fe and C resulting in the smaller structure change of the Fe nanoparticles.

    DOI PubMed

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    15
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  • Effective Heat Transfer Pathways of Thermally Conductive Networks Formed by One-Dimensional Carbon Materials with Different Sizes

    Y. S. Lee, S.-Y. Lee, K. S. Kim, S. Noda, S. E. Shim, C.-M. Yang

    Polymers   11 ( 10 ) 1661 - 1661  2019.10  [Refereed]

     View Summary

    We investigated the heat transfer behavior of thermally conductive networks with one-dimensional carbon materials to design effective heat transfer pathways for hybrid filler systems of polymer matrix composites. Nano-sized few-walled carbon nanotubes (FWCNTs) and micro-sized mesophase pitch-based carbon fibers (MPCFs) were used as the thermally conductive materials. The bulk density and thermal conductivity of the FWCNT films increased proportionally with the ultrasonication time due to the enhanced dispersibility of the FWCNTs in an ethanol solvent. The ultrasonication-induced densification of the FWCNT films led to the effective formation of filler-to-filler connections, resulting in improved thermal conductivity. The thermal conductivity of the FWCNT-MPCF hybrid films was proportional to the MPCF content (maximum thermal conductivity at an MPCF content of 60 wt %), indicating the synergistic effect on the thermal conductivity enhancement. Moreover, the MPCF-to-MPCF heat transfer pathways in the FWCNT-MPCF hybrid films were the most effective in achieving high thermal conductivity due to the smaller interfacial area and shorter heat transfer pathway of the MPCFs. The FWCNTs could act as thermal bridges between neighboring MPCFs for effective heat transfer. Furthermore, the incorporation of Ag nanoparticles of approximately 300 nm into the FWCNT-MPCF hybrid film dramatically enhanced the thermal conductivity, which was closely related to a decreased thermal interfacial resistance at the intersection points between the materials. Epoxy-based composites loaded with the FWCNTs, MPCFs, FWCNT-MPCF hybrids, and FWCNT-MPCF-Ag hybrid fillers were also fabricated. A similar trend in thermal conductivity was observed in the polymer matrix composite with carbon-based hybrid films.

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    12
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  • Stability of Chemically Doped Nanotube–Silicon Heterojunction Solar Cells: Role of Oxides at the Carbon–Silicon Interface

    Daniel D. Tune, Hiroyuki Shirae, Vincent Lami, Robert J. Headrick, Matteo Pasquali, Yana Vaynzof, Suguru Noda, Erik K. Hobbie, Benjamin S. Flavel

    ACS Applied Energy Materials   2 ( 8 ) 5925 - 5932  2019.08  [Refereed]

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    11
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  • Enhancing the photovoltaic performance of hybrid heterojunction solar cells by passivation of silicon surface via a simple 1-min annealing process

    R. Xie, N. Ishijima, H. Sugime, S. Noda

    Scientific Reports   9 ( 1 ) 12051  2019.08  [Refereed]

    Authorship:Last author, Corresponding author

     View Summary

    © 2019, The Author(s). Solution-based heterojunction technology is emerging for facile fabrication of silicon (Si)-based solar cells. Surface passivation of Si substrate has been well established to improve the photovoltaic (PV) performance for the conventional bulk Si cells. However, the impact is still not seen for the heterojunction cells. Here, we developed a facile and repeatable method to passivate the Si surface by a simple 1-min annealing process in vacuum, and integrated it into the heterojunction cells with poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) or carbon nanotube (CNT). A thin and dense oxide layer was introduced on the Si surface to provide a high-quality hole transport layer and passivation layer. The layer enhanced the power conversion efficiency from 9.34% to 12.87% (1.38-times enhancement) for the PEDOT:PSS/n-Si cells and from 6.61% to 8.52% (1.29-times enhancement) for the CNT/n-Si cells. The simple passivation is a promising way to enhance the PV performance of the Si cells with various solution-based heterojunctions.

    DOI PubMed

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    19
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  • A Semitransparent Nitride Photoanode Responsive up to λ=600 nm Based on a Carbon Nanotube Thin Film Electrode

    Daijiro Akagi, Yosuke Kageshima, Yuta Hashizume, Shigeki Aoi, Yutaka Sasaki, Hiroyuki Kaneko, Tomohiro Higashi, Takashi Hisatomi, Masao Katayama, Tsutomu Minegishi, Suguru Noda, Kazunari Domen

    ChemPhotoChem   3 ( 7 ) 521 - 524  2019.04  [Refereed]

     View Summary

    Abstract

    The development of semitransparent photoanodes is required for the construction of tandem photoelectrochemical (PEC) water splitting cells incorporating photocathodes. However, the poor stability of transparent conductive oxides at high temperatures hampers the growth of non‐oxide photoanodes with intense visible light absorption. In this work, semitransparent Ta3N5 thin film photoanodes were prepared on quartz glass substrates coated with carbon nanotubes (CNTs) by sputtering and thermal nitridation. This process makes use of the high thermal and chemical stability as well as the tunable conductivity and transmittance of CNT substrates. The photoanodic current produced by these Ta3N5 photoanodes at negative potentials is also enhanced by surface modification with Mg species. Conductive semitransparent CNT substrates such as these will assist in the development of new tandem PEC cells for water splitting.

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    13
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  • 1.5 Minute-synthesis of continuous graphene films by chemical vapor deposition on Cu foils rolled in three dimensions

    Y. Nagai, H. Sugime, S. Noda

    Chem. Eng. Sci.   201   319 - 324  2019.03  [Refereed]

    Authorship:Last author, Corresponding author

     View Summary

    © 2019 Elsevier Ltd We report a high-productivity chemical vapor deposition (CVD) process of graphene by extending the reaction field to three dimensions (3D) and shortening the CVD time to a few minutes. A large Cu foil (5 × 30 cm2) is rolled up and set in a small reactor (3.4 cm in diameter), and a continuous graphene film is obtained uniformly in a short time (1.5 min) by using C2H4 as a more reactive carbon source than the popular CH4. The graphene transferred onto a quartz glass showed optical transmittances of 94.8–96.7% (550 nm) with sheet resistances of 0.78–1.68 kΩ sq−1 (without doping) and 0.3 kΩ sq−1 (with doping by HNO3 vapor). Compared with the previous reports for fast and/or large-scale CVD, our method realized similarly high productivity of 100 cm2 min−1 based on the CVD time despite of the small reactor, and higher productivity of 0.03 cm2-graphene per cm3-reactor per minute based on the reactor volume and total time for high temperature processing (15 min for heating, 1 min for annealing, and 1.5 min for CVD). The knowledge obtained here on the CVD conditions and packing ratio of Cu foils (0.55 cm2 per cm3-reactor) is reusable for designing large-scale graphene production processes.

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    10
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  • Volumetric Discharge Capacity 1 A h cm–3 Realized by Sulfur in Carbon Nanotube Sponge Cathodes

    Keisuke Hori, Kei Hasegawa, Toshiyuki Momma, Suguru Noda

    The Journal of Physical Chemistry C   123 ( 7 ) 3951 - 3958  2019.02  [Refereed]

    Authorship:Last author, Corresponding author

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    13
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  • Direct formation of continuous multilayer graphene films with controllable thickness on dielectric substrates

    S. Akiba, M. Kosaka, K. Ohashi, K. Hasegawa, H. Sugime, S. Noda

    Thin Solid Films   675   136 - 142  2019.02  [Refereed]

    Authorship:Last author, Corresponding author

     View Summary

    © 2019 Elsevier B.V. Direct formation of graphene films on dielectric substrates is investigated by the “etching-precipitation” method which converts metal-carbon mixed films to graphene films by etching metal away by Cl 2 at 600–650 °C. Here we report a new approach for improved control of the layer number and continuity of the graphene films. Reactive sputtering of Fe in C 2 H 4 /Ar enabled fine control of the carbon concentrations and thicknesses of the initial Fe-C films, which yielded continuous multilayer graphene films of controllable average layer numbers of ~10–40, low resistivity down to ~240 μΩ cm, and high Raman G-band to D-band intensity ratio up to 16 directly on SiO 2 substrates. We also show that the carbon concentration of the initial Fe-C films determines the film continuity and crystallinity of the graphene.

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    6
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  • Carbon Nanotubes and Related Nanomaterials: Critical Advances and Challenges for Synthesis toward Mainstream Commercial Applications

    Rao, R., Pint, C.L., Islam, A.E., Weatherup, R.S., Hofmann, S., Meshot, E.R., Wu, F., Zhou, C., Dee, N., Amama, P.B., Carpena-Nu{\~n}ez, J., Shi, W., Plata, D.L., Penev, E.S., Yakobson, B.I., Balbuena, P.B., Bichara, C., Futaba, D.N., Noda, S., Shin, H., Kim, K.S., Simard, B., Mirri, F., Pasquali, M., Fornasiero, F., Kauppinen, E.I., Arnold, M., Cola, B.A., Nikolaev, P., Arepalli, S., Cheng, H.-M., Zakharov, D.N., Stach, E.A., Zhang, J., Wei, F., Terrones, M., Geohegan, D.B., Maruyama, B., Maruyama, S., Li, Y., Adams, W.W., Hart, A.J.

    ACS Nano   12 ( 12 ) 111756 - 111784  2018.12  [Refereed]

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    396
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  • Resettable Heterogeneous Catalyst: (Re)Generation and (Re)Adsorption of Ni Nanoparticles for Repeated Synthesis of Carbon Nanotubes on Ni–Al–O Thin Films

    Bin Liang, Eongyu Yi, Toshihiro Sato, Suguru Noda, Kai Sun, Dechang Jia, Yu Zhou, Richard M. Laine

    ACS Applied Nano Materials   1 ( 10 ) 5483 - 5492  2018.10  [Refereed]

    Authorship:Corresponding author

    DOI

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    2
    Citation
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  • CO2-assisted growth of millimeter-tall single-wall carbon nanotube arrays and its advantage against H2O for large-scale and uniform synthesis

    Toshihiro Sato, Hisashi Sugime, Suguru Noda

    Carbon   136   143 - 149  2018.09  [Refereed]

     View Summary

    The CO2-assisted chemical vapor deposition (CVD) is reported as a versatile method for millimeter-tall vertically-aligned single-wall carbon nanotube (VA-SWCNT) arrays when compared with the famous H2O-assisted one. The mild oxidant CO2 enabled the VA-SWCNT growth with mostly equivalent structures and yield when it was added at a much higher concentration (0.3–1 vol%) than H2O (50 ppmv). Furthermore, CO2 showed a clear advantage for the uniform growth when 18 substrates (10 × 10 mm2) were loaded in one batch. The areal yield of VA-SWCNTs decreased drastically from 1.6 to 0.4 mg cm−2 for the first 4 substrates with 50 ppmv H2O because of its depletion whereas it decreased more mildly from 1.6 to 0.8 mg cm−2 for the whole 18 substrates with 1.0 vol% CO2. The gradual decrease in the SWCNT yield with 1.0 vol% CO2 was caused by the change in the carbon source depending on its position. The mixed feed of 0.30 vol% C2H2 (being converted to SWCNTs gradually) and 3.0 vol% C2H4 (yielding C2H2 gradually) realizes the uniform growth of VA-SWCNTs for the whole 18 substrates. The CO2-assisted CVD with optimized carbon feed is promising for the uniform growth of millimeter-tall SWCNTs in large areas.

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  • An interdigitated electrode with dense carbon nanotube forests on conductive supports for electrochemical biosensors

    H. Sugime, T. Ushiyama, K. Nishimura, Y. Ohno, S. Noda

    Analyst   143 ( 15 ) 3635 - 3642  2018.06  [Refereed]

     View Summary

    © 2018 The Royal Society of Chemistry. A highly sensitive interdigitated electrode (IDE) with vertically aligned dense carbon nanotube forests directly grown on conductive supports was demonstrated by combining UV lithography and a low temperature chemical vapor deposition process (470 °C). The cyclic voltammetry (CV) measurements of K4[Fe(CN)6] showed that the redox current of the IDE with CNT forests (CNTF-IDE) reached the steady state much more quickly compared to that of conventional gold IDE (Au-IDE). The performance of the CNTF-IDE largely depended on the geometry of the electrodes (e.g. width and gap). With the optimum three-dimensional electrode structure, the anodic current was amplified by a factor of ∼18 and ∼67 in the CV and the chronoamperometry measurements, respectively. The collection efficiency, defined as the ratio of the cathodic current to the anodic current at steady state, was improved up to 97.3%. The selective detection of dopamine (DA) under the coexistence of l-ascorbic acid with high concentration (100 μM) was achieved with a linear range of 100 nM-100 μM, a sensitivity of 14.3 mA mol-1 L, and a limit of detection (LOD, S/N = 3) of 42 nM. Compared to the conventional carbon electrodes, the CNTF-IDE showed superior anti-fouling property, which is of significant importance for practical applications, with a negligible shift of the half-wave potential (ΔE1/2 < 1.4 mV) for repeated CV measurements of DA at high concentration (100 μM).

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  • Flame-assisted chemical vapor deposition for continuous gas-phase synthesis of 1-nm-diameter single-wall carbon nanotubes

    S. Okada, H. Sugime, K. Hasegawa, T. Osawa, S. Kataoka, H. Sugiura, S. Noda

    Carbon   138   1 - 7  2018.05  [Refereed]

     View Summary

    © 2018 The Authors Flame synthesis enables the mass-production of carbon black and fullerene but not of carbon nanotubes (CNTs) due to the narrow window for producing CNTs while preventing tar generation. We report a flame-assisted chemical vapor deposition method, in which a premixed flame is used for the instantaneous generation of floating catalysts, the heating of the gas, and the growth of single-wall CNTs (SWCNTs) using a furnace at the downstream of the flame. This method yields high quality SWCNTs with a small average diameter of 0.96 nm, a small diameter deviation of 0.21 nm, and a high carbon purity of ∼90 wt%. Multiple parameters affect the SWCNT production significantly, which are investigated systematically and optimized carefully. The effects and possible mechanisms of the key parameters are discussed.

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  • Carbon Nanotube Web with Carboxylated Polythiophene "assist" for High-Performance Battery Electrodes

    Yo Han Kwon, Jung Jin Park, Lisa M. Housel, Krysten Minnici, Guoyan Zhang, Sujin R. Lee, Seung Woo Lee, Zhongming Chen, Suguru Noda, Esther S. Takeuchi, Kenneth J. Takeuchi, Amy C. Marschilok, Elsa Reichmanis

    ACS Nano   12 ( 4 ) 3126 - 3139  2018.04  [Refereed]

     View Summary

    A carbon nanotube (CNT) web electrode comprising magnetite spheres and few-walled carbon nanotubes (FWNTs) linked by the carboxylated conjugated polymer, poly[3-(potassium-4-butanoate) thiophene] (PPBT), was designed to demonstrate benefits derived from the rational consideration of electron/ion transport coupled with the surface chemistry of the electrode materials components. To maximize transport properties, the approach introduces monodispersed spherical Fe3O4 (sFe3O4) for uniform Li+ diffusion and a FWNT web electrode frame that affords characteristics of long-ranged electronic pathways and porous networks. The sFe3O4 particles were used as a model high-capacity energy active material, owing to their well-defined chemistry with surface hydroxyl (-OH) functionalities that provide for facile detection of molecular interactions. PPBT, having a π-conjugated backbone and alkyl side chains substituted with carboxylate moieties, interacted with the FWNT π-electron-rich and hydroxylated sFe3O4 surfaces, which enabled the formation of effective electrical bridges between the respective components, contributing to efficient electron transport and electrode stability. To further induce interactions between PPBT and the metal hydroxide surface, polyethylene glycol was coated onto the sFe3O4 particles, allowing for facile materials dispersion and connectivity. Additionally, the introduction of carbon particles into the web electrode minimized sFe3O4 aggregation and afforded more porous FWNT networks. As a consequence, the design of composite electrodes with rigorous consideration of specific molecular interactions induced by the surface chemistries favorably influenced electrochemical kinetics and electrode resistance, which afforded high-performance electrodes for battery applications.

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  • Millimeter-tall carbon nanotube arrays grown on aluminum substrates

    Shota Miura, Yu Yoshihara, Mayu Asaka, Kei Hasegawa, Hisashi Sugime, Aun Ota, Hisayoshi Oshima, Suguru Noda

    Carbon   133   77  2018.04  [Refereed]

     View Summary

    The authors regret that the incorrect version of the Graphical Abstract was included with this article. The figures within the article are correct. The correct Graphical Abstract appears below: [Figure presented] The authors would like to apologise for any inconvenience caused.

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  • Millimeter-tall carbon nanotube arrays grown on aluminum substrates

    Shota Miura, Yu Yoshihara, Mayu Asaka, Kei Hasegawa, Hisashi Sugime, Aun Ota, Hisayoshi Oshima, Suguru Noda

    Carbon   130   834 - 842  2018.04

     View Summary

    Millimeter-tall vertically aligned carbon nanotubes (VA-CNTs) were grown directly on Al substrates. Atmospheric pressure chemical vapor deposition is performed at 600 °C, which is well below the melting point of Al (660 °C), using Fe catalyst and C2H2 as a highly reactive carbon feedstock. The CNT height was sensitive to the C2H2 concentration and 0.06 vol% was optimum for balanced growth rate and catalyst lifetime, yielding 0.06 mm-tall VA-CNTs in 2 h. The CO2 addition at 1.8 vol% to the C2H2/Ar gas significantly enhanced the CNT growth, yielding 1.1 mm-tall VA-CNTs in 12 h. CO2 shows this remarkable effect when added in large excess to C2H2, differently from the well-known method of “small addition of water.” Moreover, the resulting VA-CNTs showed electrical contact with the Al sheets with resistance of ≤0.7 Ω cm−2. The effect of CO2 is systematically studied and discussed.

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  • Self-supporting hybrid supercapacitor electrodes based on carbon nanotube and activated carbons

    Temirgaliyeva, T.S., Kuzuhara, S., Noda, S., Nazhipkyzy, M., Kerimkulova, A.R., Lesbayev, B.T., Prikhodko, N.G., Mansurov, Z.A.

    Eurasian Chemico-Technological Journal   20 ( 3 )  2018

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  • Improved capacity of redox-active functional carbon cathodes by dimension reduction for hybrid supercapacitors

    Tianyuan Liu, Byeongyong Lee, Michael J. Lee, Jinho Park, Zhongming Chen, Suguru Noda, Seung Woo Lee

    Journal of Materials Chemistry A   6 ( 8 ) 3367 - 3375  2018

     View Summary

    Hybrid supercapacitors, which combine the advantages of supercapacitors and rechargeable batteries, have the potential to meet the demands of both high-energy and -power in electrochemical energy storage systems. However, the energy density of the hybrid supercapacitors has been limited because of the low capacity of the activated carbon cathode. Here we introduce a high-capacity carbon cathode containing plenty of oxygen functional groups that are redox-active towards both Li- and Na-ions. This functional carbon has an ultra-thin two-dimensional structure that has significant advantages in utilizing the redox reactions. The functional carbon cathode can exhibit very high capacities of ∼250 mA h g-1 in Li-cells and ∼210 mA h g-1 in Na-cells. A hybrid supercapacitor consisting of the two-dimensional functional carbon cathode with a commercial level loading density of ∼9.3 mg cm-2 and a Si-based anode delivers a high-energy density of ∼182 W h kg-1 at a high-power density of 1 kW kg-1.

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    30
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  • Self-supporting S@GO-FWCNTs composite films as positive electrodes for high-performance lithium-sulfur batteries

    Lifeng Cui, Yanan Xue, Suguru Noda, Zhongming Chen

    RSC Advances   8 ( 5 ) 2260 - 2266  2018

     View Summary

    Although lithium-sulfur (Li-S) batteries are a promising secondary power source, it still faces many technical challenges, such as rapid capacity decay and low sulfur utilization. The loading of sulfur and the weight percentage of sulfur in the cathode usually have a significant influence on the energy density. Herein, we report an easy synthesis of a self-supporting sulfur@graphene oxide-few-wall carbon nanotube (S@GO-FWCNT) composite cathode film, wherein an aluminum foil current collector is replaced by FWCNTs and sulfur particles are uniformly wrapped by graphene oxide along with FWCNTs. The 10 wt% FWCNT matrix through ultrasonication not only provided self-supporting properties without the aid of metallic foil, but also increased the electrical conductivity. The resulting S@GO-FWCNT composite electrode showed high rate performance and cycle stability up to ∼385.7 mA h gelectrode -1 after 500 cycles and close to ∼0.04% specific capacity degradation per cycle, which was better than a S@GO composite electrode (353.1 mA h gelectrode -1). This S@GO-FWCNT composite self-supporting film is a promising cathode material for high energy density rechargeable Li-S batteries.

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  • Critical effect of nanometer-size surface roughness of a porous Si seed layer on the defect density of epitaxial Si films for solar cells by rapid vapor deposition

    Kei Hasegawa, Chiaki Takazawa, Makoto Fujita, Suguru Noda, Manabu Ihara

    CrystEngComm   20 ( 13 ) 1774 - 1778  2018  [Refereed]

     View Summary

    Monocrystalline, low-defect density Si thin films were successfully fabricated via epitaxy with 1 minute rapid vapor deposition on a porous seed layer. Zone heating recrystallization reduced the surface roughness of the seed layer to sub-nanometer size. The critical effect of roughness on the defect density of epitaxial films was confirmed.

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  • A-few-second synthesis of silicon nanoparticles by gas-evaporation and their self-supporting electrodes based on carbon nanotube matrix for lithium secondary battery anodes

    Takayuki Kowase, Keisuke Hori, Kei Hasegawa, Toshiyuki Momma, Suguru Noda

    JOURNAL OF POWER SOURCES   363   450 - 459  2017.09  [Refereed]

     View Summary

    Rapid gas-evaporation method is proposed and developed, which yields Si nanoparticles (SiNPs) in a few seconds at high yields of 20%-60% from inexpensive and safe bulk Si. Such rapid process is realized by heating the Si source to a temperature &gt;= 2000 degrees C, much higher than the melting point of Si (1414 degrees C). The size of SiNPs is controlled at tens to hundreds nanometers simply by the Ar gas pressure during the evaporation process. Self-supporting films are fabricated simply by co-dispersion and filtration of the SiNPs and carbon nanotubes (CNTs) without using binders nor metal foils. The half-cell tests showed the improved performances of the SiNP-CNT composite films as anode when coated with graphitic carbon layer. Their performances are evaluated with various SiNP sizes and Si/CNT ratios systematically. The SiNP-CNT film with a Si/CNT mass ratio of 4 realizes the balanced film-based capacities of 618 mAh/g(film), 230 mAh/cm(3), and 0.644 mAh/cm(2) with a moderate Si-based performance of 863 mAh/g(Si) at the 100th cycle. (C) 2017 Elsevier B.V. All rights reserved.

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  • Ten-Second Epitaxy of Cu on Repeatedly Used Sapphire for Practical Production of High-Quality Graphene

    Yukuya Nagai, Asahi Okawa, Taisuke Minamide, Kei Hasegawa, Hisashi Sugime, Suguru Noda

    ACS Omega   2 ( 7 ) 3354 - 3362  2017.07

     View Summary

    Epitaxial copper (Cu) films yield graphene with superior quality but at high cost. We report 1-3 μm thick epitaxial Cu films prepared on c plane sapphire substrates in 10-30 s, which is much faster than that of the typical sputtering method. Such rapid deposition is realized by vapor deposition using a Cu source heated to 1700-1800 °C, which is much higher than its melting point of 1085 °C. Continuous graphene films, either bilayer or single-layer, are obtained on the epitaxial Cu by chemical vapor deposition and transferred to carrier substrates. The sapphire substrates can be reused five to six times maintaining the quality of the epitaxial Cu films and graphene. The mechanisms and requirements are discussed for such quick epitaxy of Cu on reused sapphire, which will enable high-quality graphene production at lower cost.

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  • Catalyst nucleation and carbon nanotube growth. from flame-synthesized Co-A1-O nanopowders at ten-second time scale

    Hiroyuki Shirae, Kei Hasegawa, Hisashi Sugime, Eongyu Yi, Richard M. Laine, Suguru Noda

    CARBON   114   31 - 38  2017.04  [Refereed]

     View Summary

    Flame-synthesized (CoO)(x)(Al2O3)(1-x) spinel nanopowders with primary particles of similar to 20 nm were used to grow small diameter carbon nanotubes (CNTs). The nanopowders with x &lt;= 035 grew few CNTs whereas that with x = 0.65 grew CNTs efficiently. Low crystalline and large-diameter multi-wall CNTs grew by annealing and chemical vapor deposition (CVD) at 800 degrees C for similar to 10 min, whereas single-wall CNTs with high crystallinity (G-band to D-band intensity ratio of 20-100 by Raman spectroscopy) grew by annealing and CVD at &gt;= 1000 degrees C for similar to 10 s. The excess Co in the spinel reduced and segregated to form multiple Co nanoparticles on the surface of the single primary alumina nanoparticles in similar to 10 s, yielding SWCNTs in similar to 10 s. Such flame synthesized nanopowders, reduced and activated by H-2, provide CNTs from C2H2, all in ten-second time scale, and as such are promising for practical, high-through-put production of small-diameter CNTs. (C) 2016 Elsevier Ltd. All rights reserved.

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  • Highly air- and moisture-stable hole-doped carbon nanotube films achieved using boron-based oxidant

    Kazuma Funahashi, Naoki Tanaka, Yoshiaki Shoji, Naoki Imazu, Ko Nakayama, Kaito Kanahashi, Hiroyuki Shirae, Suguru Noda, Hiromichi Ohta, Takanori Fukushima, Taishi Takenobu

    APPLIED PHYSICS EXPRESS   10 ( 3 )  2017.03  [Refereed]

     View Summary

    Hole doping into carbon nanotubes can be achieved. However, the doped nanotubes usually suffer from the lack of air and moisture stability, thus, they eventually lose their improved electrical properties. Here, we report that a salt of the two-coordinate boron cation Mes(2)B(+) (Mes: 2,4,6-trimethylphenyl group) can serve as an efficient hole-doping reagent to produce nanotubes with markedly high stability in the presence of air and moisture. Upon doping, the resistances of the nanotubes decreased, and these states were maintained for one month in air. The hole-doped nanotube films showed a minimal increase in resistance even upon humidification with a relative humidity of 90%. (C) 2017 The Japan Society of Applied Physics

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  • Self-polymerized dopamine as an organic cathode for Li- and Na-ion batteries

    Tianyuan Liu, Ki Chul Kim, Byeongyong Lee, Zhongming Chen, Suguru Noda, Seung Soon Jang, Seung Woo Lee

    ENERGY & ENVIRONMENTAL SCIENCE   10 ( 1 ) 205 - 215  2017.01  [Refereed]

     View Summary

    Self-polymerized dopamine is a versatile coating material that has various oxygen and nitrogen functional groups. Here, we demonstrate the redox-active properties of self-polymerized dopamine on the surface of few-walled carbon nanotubes (FWNTs), which can be used as organic cathode materials for both Li-and Na-ion batteries. We reveal the multiple redox reactions between self-polymerized dopamine and electrolyte ions in the high voltage region from 2.5 to 4.1 V vs. Li using both density functional theory (DFT) calculations and electrochemical measurements. Free-standing and flexible hybrid electrodes are assembled using a vacuum filtration method, which have a 3D porous network structure consisting of polydopamine coated FWNTs. The hybrid electrodes exhibit gravimetric capacities of similar to 133 mA h g(-1) in Li-cells and similar to 109 mA h g(-1) in Na-cells utilizing double layer capacitance from FWNTs and multiple redox-reactions from polydopamine. The polydopamine itself within the hybrid film can store high gravimetric capacities of similar to 235 mA h g(-1) in Li-cells and similar to 213 mA h g(-1) in Na-cells. In addition, the hybrid electrodes show a high rate-performance and excellent cycling stability, suggesting that self-polymerized dopamine is a promising cathode material for organic rechargeable batteries.

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  • Lithium ion batteries made of electrodes with 99 wt% active materials and 1 wt% carbon nanotubes without binder or metal foils

    Kei Hasegawa, Suguru Noda

    JOURNAL OF POWER SOURCES   321   155 - 162  2016.07  [Refereed]

     View Summary

    Herein, we propose lithium ion batteries (LIBs) without binder or metal foils, based on a three-dimensional carbon nanotube (CNT) current collector. Because metal foils occupy 20-30 wt% of conventional LIBs and the polymer binder has no electrical conductivity, replacing such non-capacitive materials is a valid approach for improving the energy and power density of LIBs. Adding only 1 wt% of few-wall CNTs to the active material enables flexible freestanding sheets to be fabricated by simple dispersion and filtration processes. Coin cell tests are conducted on full cells fabricated from a 99 wt% LiCoO2-1 wt% CNT cathode and 99 wt% graphite-1 wt% CNT anode. Discharge capacities of 353 and 306 mAh g(graphite)(-1) are obtained at charge-discharge rates of 37.2 and 372 mA g(graphite)(-1) respectively, with a capacity retention of 65% at the 500th cycle. The suitability of the 1 wt% CNT-based composite electrodes for practical scale devices is demonstrated with laminate cells containing 50 x 50 mm(2) electrodes. Use of metal combs instead of metal foils enables charge-discharge operation of the laminate cell without considerable IR drop. Such electrodes will minimize the amount of metal and maximize the amount of active materials contained in LIBs. (C) 2016 Elsevier B.V. All rights reserved.

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  • Biomass-derived carbonaceous positive electrodes for sustainable lithium-ion storage

    Tianyuan Liu, Reza Kavian, Zhongming Chen, Samuel S. Cruz, Suguru Noda, Seung Woo Lee

    NANOSCALE   8 ( 6 ) 3671 - 3677  2016.02  [Refereed]

     View Summary

    Biomass derived carbon materials have been widely used as electrode materials; however, in most cases, only electrical double layer capacitance (EDLC) is utilized and therefore, only low energy density can be achieved. Herein, we report on redox-active carbon spheres that can be simply synthesized from earth-abundant glucose via a hydrothermal process. These carbon spheres exhibit a specific capacity of similar to 210 mA h g(CS)(-1), with high redox potentials in the voltage range of 2.2-3.7 V vs. Li, when used as positive electrode in lithium cells. Free-standing, flexible composite films consisting of the carbon spheres and few-walled carbon nanotubes deliver high specific capacities up to similar to 155 mA h g(electrode)(-1) with no obvious capacity fading up to 10 000 cycles, proposing to be promising positive electrodes for lithium-ion batteries or capacitors. Furthermore, considering that the carbon spheres were obtained in an aqueous glucose solution and no toxic or hazardous reagents were used, this process opens up a green and sustainable method for designing high performance, environmentally-friendly energy storage devices.

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  • A Color-Tunable Polychromatic Organic-Light-Emitting-Diode Device With Low Resistive Intermediate Electrode for Roll-to-Roll Manufacturing

    Takatoshi Tsujimura, Takeshi Hakii, Suguru Noda

    IEEE TRANSACTIONS ON ELECTRON DEVICES   63 ( 1 ) 402 - 407  2016.01  [Refereed]

     View Summary

    A flexible organic-light-emitting diode (OLED) with capability to show 16 million colors is fabricated on plastic barrier-film substrate, which can produce arbitrary shape with arbitrary colors, suitable for artistic expressions. Independently controlled red, green, and blue light-emitting layers are stacked vertically, so that no visible structure can be observed even with magnifiers from right-in-front measurement. In the past, large voltage drop of intermediate electrode was preventing this approach to be applied to actual electronic devices. However, according to the surface mobility control using Fick's law analysis, low sheet resistance 7.34 Omega/square on plastic film is developed, so that 7.17-cm(2) area emission is successfully achieved. With optical length optimization for each color stack, more than 100% color reproduction in National Television Committee Standard is achieved by stack design. The device can be used for colored illumination, as well as for organic-light-emitting display pixels for three times emission than the conventional pixel design. The device is fabricated on plastic substrate, so that the polychromatic OLED device is manufacturable with roll-to-roll production line.

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  • Carbon nanotube-silicon heterojunction solar cells with surface-textured Si and solution-processed carbon nanotube films

    Eri Muramoto, Yuhei Yamasaki, Feijiu Wang, Kei Hasegawa, Kazunari Matsuda, Suguru Noda

    RSC ADVANCES   6 ( 96 ) 93575 - 93581  2016  [Refereed]

     View Summary

    Carbon nanotube (CNT)-silicon (Si) heterojunction solar cells are fabricated with surface-textured Si substrates. Using a dilute alkaline solution, common etchant in the Si solar cell industry, we formed a pyramidal texture on the Si substrate surface. The texture effectively enhances the absorption of the incident light, improving the short-circuit current density by similar to 1.3-fold, up to 33.1 mA cm(-2). We fabricated CNT-Si solar cells with a power conversion efficiency (PCE) of 10.4% without any anti-reflective coatings or doping of the CNTs. Moreover, the CNT films were prepared from commercialized CNT agglomerates by a mild solution-based process, which is well suited for the fabrication of CNT-Si solar cells with large area. We also achieved a PCE of 9.57% for a flat cell with careful removal of surfactant from and doping by nitric acid of the CNT films. These findings suggest that with the combination of surface-textured Si and solution-processed CNT films, efficient and low-cost CNT-Si solar cells may be realized.

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  • 50-100 mu m-thick pseudocapacitive electrodes of MnO2 nanoparticles uniformly electrodeposited in carbon nanotube papers

    Misato Narubayashi, Zhongming Chen, Kei Hasegawa, Suguru Noda

    RSC ADVANCES   6 ( 47 ) 41496 - 41505  2016  [Refereed]

     View Summary

    To overcome the tradeoff between the gravimetric capacitance and loading density of pseudocapacitive MnO2, we electrodeposited MnO2 nanoparticles on the carbon nanotube (CNT) surfaces in 18-37 mu m thick self-supporting CNT papers. We examined the electrodeposition conditions including constant potential, constant current, and potential pulses, and obtained MnO2-CNT hybrid electrodes containing MnO2 nanoparticles uniformly deposited at 60-90 wt% with an expanded CNT matrix. The MnO2-CNT hybrid electrode with a thickness of 62 mu m, density of 1.09 g cm(-3), areal mass of 6.75 mg cm(-2), and 82 wt% MnO2 load showed a total gravimetric capacitance of 120 and 51 F-total g(electrode)(-1), volumetric capacitance of 131 and 56 F-total cm(-3) and areal capacitance of 0.81 and 0.34 Ftotal cm(-2) at scan rates of 2 and 200 mV s(-1), respectively. The large thickness, moderately high mass density, and fairly conductive CNT matrix realized such high values of gravimetric, areal and volumetric capacitances that are important for practical devices.

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    14
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  • Rapid vapour deposition and in situ melt crystallization for 1 min fabrication of 10 mu m-thick crystalline silicon films with a lateral grain size of over 100 mu m

    Y. Yamasaki, K. Hasegawa, T. Osawa, S. Noda

    CRYSTENGCOMM   18 ( 19 ) 3404 - 3410  2016  [Refereed]

     View Summary

    We developed a film deposition method which yielded continuous polycrystalline Si films with large lateral grain sizes of over 100 mu m and thicknesses of similar to 10 mu m in 1 min on growth substrates other than silicon wafers in a single-step process. The silicon source is heated to similar to 2000 degrees C, much higher than the melting point of Si, which enables a high deposition rate. Controlling the temperature of the growth substrate, initially above and later below the melting point of Si, allows the seamless lateral to vertical growth of crystalline silicon grains. Thermally and chemically stable substrates of quartz glass and alumina with a 0.1 mu m-thick amorphous carbon layer were effective; liquid silicon wetted well by forming a thin SiC interlayer while substrates stayed stable. Such large-grain polycrystalline silicon films synthesized rapidly in 1 min may be used for low-cost, stable and flexible thin film photovoltaic cells.

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    6
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  • Hierarchical networks of redox-active reduced crumpled graphene oxide and functionalized few-walled carbon nanotubes for rapid electrochemical energy storage

    Byeongyong Lee, Chongmin Lee, Tianyuan Liu, Kwangsup Eom, Zhongming Chen, Suguru Noda, Thomas F. Fuller, Hee Dong Jang, Seung Woo Lee

    NANOSCALE   8 ( 24 ) 12330 - 12338  2016  [Refereed]

     View Summary

    Crumpled graphene is known to have a strong aggregation-resistive property due to its unique 3D morphology, providing a promising solution to prevent the restacking issue of graphene based electrode materials. Here, we demonstrate the utilization of redox-active oxygen functional groups on the partially reduced crumpled graphene oxide (r-CGO) for electrochemical energy storage applications. To effectively utilize the surface redox reactions of the functional groups, hierarchical networks of electrodes including r-CGO and functionalized few-walled carbon nanotubes (f-FWNTs) are assembled via a vacuum-filtration process, resulting in a 3D porous structure. These composite electrodes are employed as positive electrodes in Li-cells, delivering high gravimetric capacities of up to similar to 170 mA h g(-1) with significantly enhanced rate-capability compared to the electrodes consisting of conventional 2D reduced graphene oxide and f-FWNTs. These results highlight the importance of microstructure design coupled with oxygen chemistry control, to maximize the surface redox reactions on functionalized graphene based electrodes.

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  • Nano-scalc smoothing of double layer porous Si substrates for detaching and fabricating low cost, high efficiency monocrystalline thin film Si solar cell by zone heating recrystallization

    Chiaki Takazawa, Makoto Fujita, Kei Hasegawa, Anatolli Lukianov, Xiaomei Zhang, Suguru Noda, Manabu Ihara

    ECS Transactions   75 ( 31 ) 11 - 23  2016  [Refereed]

     View Summary

    A fabrication process of monocrystalline thin films for Si solar cells was developed that uses epitaxial growth and layer transfer process for low fabrication cost and high photoelectric conversion efficiency. Fabrication of high crystalline epitaxial thin films requires controlling the surface roughness and pore size of the seed layer in nano-level, double layer porous Si (DLPS). By using this zone heating recrystallization (ZHR) method, in which the top surface of DLPS is selectively annealed by scanning upper lamp heater, we successfully reduced the surface roughness and pore size. By using the rapid vapor deposition (RVD) method, we fabricated an epitaxial monocrystalline Si thin film in 1 mm on the ZHR-treated DLPS and then easily detached this thin film from the substrate. The crystal distortion of epitaxial Si thin films can be controlled by using ZHR to smooth and change only the top surface of DLPS.

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  • Denser and taller carbon nanotube arrays on Cu foils useable as thermal interface materials

    Nuri Na, Kei Hasegawa, Xiaosong Zhou, Mizuhisa Nihei, Suguru Noda

    JAPANESE JOURNAL OF APPLIED PHYSICS   54 ( 9 )  2015.09  [Refereed]

     View Summary

    To achieve denser and taller carbon nanotube (CNT) arrays on Cu foils, catalyst and chemical vapor deposition (CVD) conditions were carefully engineered. CNTs were grown to similar to 50 mu m using Fe/TiN/Ta catalysts in which Ta and TiN acted as diffusion barriers for Cu and Ta, respectively. A tradeoff was found between the mass density and height of the CNT arrays, and CNT arrays with a mass density of 0.30 g cm(-3) and height of 45 mu m were achieved under optimized conditions. Thermal interface materials (TIMs) with CNT array/Cu foil/CNT array structures showed decreasing thermal resistance from 86 to 24 mm(2) K W-1 with increasing CNT array mass densities from 0.07-0.08 to 0.19-0.26 g cm(-3) for Cu and Al blocks with surfaces as rough as 20-30 mu m. The best CNT/Cu/CNT TIMs showed thermal resistance values comparable to that of a typical indium sheet TIM. (C) 2015 The Japan Society of Applied Physics

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  • Overcoming the quality-quantity tradeoff in dispersion and printing of carbon nanotubes by a repetitive dispersion-extraction process

    Hiroyuki Shirae, Dong Young Kim, Kei Hasegawa, Taishi Takenobu, Yutaka Ohno, Suguru Noda

    CARBON   91   20 - 29  2015.09  [Refereed]

     View Summary

    Dispersion-printing processes are essential for the fabrication of various devices using carbon nanotubes (CNTs). Insufficient dispersion results in CNT aggregates, while excessive dispersion results in the shortening of individual CNTs. To overcome this tradeoff, we propose here a repetitive dispersion-extraction process for CNTs. Long-duration ultrasonication (for 100 min) produced an aqueous dispersion of CNTs with sodium dodecylbenzene sulfonate with a high yield of 64%, but with short CNT lengths (a few mu m), and poor conductivity in the printed films (similar to 450 S cm(-1)). Short-duration ultrasonication (for 3 min) yielded a CNT dispersion with a very small yield of 2.4%, but with long CNTs (up to 20-40 mu m), and improved conductivity in the printed films (2200 S cm(-1)). The remaining sediment was used for the next cycle after the addition of the surfactant solution. 90% of the CNT aggregates were converted into conductive CNT films within 13 cycles (i.e., within 39 min), demonstrating the improved conductivity and reduced energy/time requirements for ultrasonication. CNT lines with conductivities of 1400-2300 S cm(-1) without doping and sub-100 mu m width, and uniform CNT films with 80% optical transmittance and 50 Omega/sq sheet resistance with nitric acid doping were obtained on polyethylene terephthalate films. (C) 2015 Elsevier Ltd. All rights reserved.

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  • One-minute deposition of micrometre-thick porous Si-Cu anodes with compositional gradients on Cu current collectors for lithium secondary batteries

    Jungho Lee, Kei Hasegawa, Toshiyuki Momma, Tetsuya Osaka, Suguru Noda

    JOURNAL OF POWER SOURCES   286   540 - 550  2015.07  [Refereed]

     View Summary

    We report micrometre-thick porous Si-Cu anodes that are rapidly co-deposited on Cu current collectors in 1 mm. This rapid deposition is realized by heating Si and Cu powders to similar to 2000 degrees C and elevating their vapour pressures, while the porous and amorphous anode structure is realized by keeping the substrates at 100 degrees C. The films spontaneously form a 2-4.5-mu m-thick composition gradient that changes from a Cu-rich region at the bottom to a Si-rich region at the top of the film, because of the higher vapour pressure for Cu than Si. A small addition of 5 wt% Cu to the Si source enhances the cycle performance of the film remarkably in a half-cell test, yielding a gravimetric capacity of 1250 mAh g(film)(-1), a volumetric capacity of 1956 mAh cm(film)(-3), and an areal capacity of 0.96 mAh cm(anode)(-2) at the 100th cycle. However, excess addition of Cu causes partial Si crystallization in the films, which results in poorer cycle performance. While further improvement is needed, this rapid vapour deposition method yields Si-Cu films with compositional gradients on Cu current collectors in 1 min using inexpensive and safe Si and Cu powder sources, and is attractive for practical Si-based anode fabrication. (C) 2015 Elsevier B.V. All rights reserved.

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    15
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  • Electrochemical polymerization of pyrene derivatives on functionalized carbon nanotubes for pseudocapacitive electrodes

    John C. Bachman, Reza Kavian, Daniel J. Graham, Dong Young Kim, Suguru Noda, Daniel G. Nocera, Yang Shao-Horn, Seung Woo Lee

    NATURE COMMUNICATIONS   6   7040  2015.05  [Refereed]

     View Summary

    Electrochemical energy-storage devices have the potential to be clean and efficient, but their current cost and performance limit their use in numerous transportation and stationary applications. Many organic molecules are abundant, economical and electrochemically active; if selected correctly and rationally designed, these organic molecules offer a promising route to expand the applications of these energy-storage devices. In this study, polycyclic aromatic hydrocarbons are introduced within a functionalized few-walled carbon nanotube matrix to develop high-energy, high-power positive electrodes for pseudocapacitor applications. The reduction potential and capacity of various polycyclic aromatic hydrocarbons are correlated with their interaction with the functionalized few-walled carbon nanotube matrix, chemical configuration and electronic structure. These findings provide rational design criteria for nanostructured organic electrodes. When combined with lithium negative electrodes, these nanostructured organic electrodes exhibit energy densities of similar to 350 Wh kg(electrode)(-1) at power densities of similar to 10 kW kg(electrode)(-1) for over 10,000 cycles.

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    133
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  • Direct synthesis of few- and multi-layer graphene films on dielectric substrates by "etching-precipitation" method

    Masaki Kosaka, Soichiro Takano, Kei Hasegawa, Suguru Noda

    CARBON   82   254 - 263  2015.02  [Refereed]

     View Summary

    A novel "etching-precipitation" method is proposed and developed for the direct synthesis of graphene on dielectric substrates. In this method, graphene precipitates from the Fe-C solid solution film during selective etching of Fe using Cl-2 gas. Few-and multi-layer graphene is fabricated directly on quartz glass and SiO2/Si substrates without Fe residue at a growth temperature of 500-650 degrees C, which is a significantly lower temperature than used in the conventional chemical vapor deposition method. The 6- to 7-layer graphene synthesized at 650 degrees C shows a volume resistivity of 80-140 mu Omega cm. The average number of layers can be easily controlled in a linear fashion with the initial carbon feed, which is proportional to the thickness of the starting Fe-C films. Line-patterned multi-layer graphene is also fabricated by simply pre-patterning the starting Fe-C film although its structure is somewhat different from typical graphene ribbons. "Etching-precipitation" will be a practical route to synthesize graphene with micro-patterns directly onto device substrates of arbitrary sizes. (C) 2014 Elsevier Ltd. All rights reserved.

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    32
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  • Simple and engineered process yielding carbon nanotube arrays with 1.2 x 10(13) cm(-2) wall density on conductive underlayer at 400 degrees C

    Nuri Na, Dong Young Kim, Yeong-Gi So, Yuichi Ikuhara, Suguru Noda

    CARBON   81   773 - 781  2015.01  [Refereed]

     View Summary

    A simple process is presented that realizes carbon nanotube (CNT) arrays that meet the process and structure requirements for use in large-scale integrated circuits. Ni particles are formed densely on a conductive TiN layer on SiO2/Si substrates through nucleation and growth by sputtering, which was stopped prior to percolation of the Ni particles. Ni particles as dense as 2.8 x 10(12) cm(-2) were formed after annealing at 400 degrees C and chemical vapor deposition (CVD) was carried out at 400 degrees C by feeding C2H2 at partial pressures as low as 0.13-1.3 Pa so as not to kill the catalyst. Scanning electron microscopy with energy dispersive X-ray spectroscopy revealed the mass density of the arrays to be as high as 1.1 g cm(-3). High resolution transmission electron microscopy showed the densely packed CNTs with an average wall number of eight. Atomic force microscopy of the root of the CNT arrays transferred to a SiO2/Si substrate enabled direct counting of individual CNTs, revealing areal densities of CNTs and CNT walls as high as 1.5 x 10(12) and 1.2 x 10(13) cm(-2), respectively. The simple process, using conventional sputtering and CVD apparatus, with carefully engineered conditions offers a route for practical application of CNTs. (C) 2014 Elsevier Ltd. All rights reserved.

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    26
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  • One-minute deposition of micrometre-thick porous Si anodes for lithium ion batteries

    Jungho Lee, Suguru Noda

    RSC ADVANCES   5 ( 4 ) 2938 - 2946  2015  [Refereed]

     View Summary

    We report the rapid vapour deposition of 3-14 mu m-thick porous Si anodes on Cu current collectors in 10-60 s. Such rapid deposition was achieved by heating the Si source to over 2000 degrees C, well above the melting point of Si, while the porous structure was realized in the deposited Si films by keeping the Cu collector at a much lower temperature of 100-500 degrees C. The adhesion between the Cu collectors and Si films was enhanced by forming a CuSix intermixed layer by post-deposition annealing as well as surface treatment of the Cu collectors. Half-cell measurements showed that the porous Si anodes without post-annealing degraded in a few cycles. A markedly improved cycle performance (1000 mA h g(Si)(-1) and 0.66 mA h cm(anode)(-2) at the anode for the 50th cycle) was achieved for post-annealed 3.5 mu m-thick porous Si films. Rapid vapor deposition of micrometre-thick porous Si films using inexpensive, safe Si powder is a practical route to fabricate high-capacity anodes for lithium ion batteries.

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    7
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  • Important factors for effective use of carbon nanotube matrices in electrochemical capacitor hybrid electrodes without binding additives

    Ricardo Quintero, Dong Young Kim, Kei Hasegawa, Yuki Yamada, Atsuo Yamada, Suguru Noda

    RSC ADVANCES   5 ( 21 ) 16101 - 16111  2015  [Refereed]

     View Summary

    Various capacitive particles are currently available for use in electrochemical capacitors, but their electrical conductivities are typically low and require enhancement. Carbon nanotube (CNT) matrices can be used to fabricate self-supporting electrodes without binding or conducting additives. Herein, liquid dispersion and subsequent vacuum filtration were used to prepare thick (similar to 100 mu m) hybrid electrodes of activated carbon (AC) and CNTs. Factors including CNT type, AC particle size, solvent, and surfactant strongly affected the capacitance and rate performance of the hybrid electrodes. Different solvents and types of CNTs were best suited for pure CNT electrodes and AC-CNT hybrid electrodes; single-wall CNTs (SWCNTs) with a strong dispersant produced CNT electrodes with the best performance among pure CNT electrodes. Meanwhile, few-wall CNTs (FWCNTs) with a weak dispersant produced AC-CNT hybrid electrodes with the best performance among hybrid electrodes. Addition of 10 wt% FWCNTs to AC yielded a self-supporting hybrid electrode with improved performance (132 F g(-1), 58 F cm(-3), 0.70 F cm(-2) at 100 mV s(-1)) compared with that of a conventional AC electrode with conducting and binding additives (74 F g(-1), 26 F cm(-3), 0.60 F cm(-2) at 100 mV s(-1)), and a pure electrode of expensive SWCNTs (52 F g(-1), 26 F cm(-3), 0.26 F cm(-2) at 100 mV s(-1)).

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    11
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  • Over 99.6 wt%-pure, sub-millimeter-long carbon nanotubes realized by fluidized-bed with careful control of the catalyst and carbon feeds

    Zhongming Chen, Dong Young Kim, Kei Hasegawa, Toshio Osawa, Suguru Noda

    CARBON   80   339 - 350  2014.12  [Refereed]

     View Summary

    To establish a method for sub-second conversion of acetylene to sub-millimeter-long carbon nanotubes (CNTs), we have proposed and developed an internal heat-exchange reactor for fluidized-bed chemical vapor deposition (FBCVD). This reactor enabled sufficient heating of the reaction gas and uniform heating of the bed of alumina beads at a space velocity as high as 3600 h(-1). The direct feeding of the catalyst vapors (aluminum isopropoxide for the alumina support layer and ferrocene for the iron particles) to the bed separately from the other gases, which were fed through the heat-exchange and preheating zone and the distributer, enabled the careful control of the catalyst particles deposited on the beads. By decreasing the acetylene feed concentration and preventing the deactivation of small Fe particles, we realized semi-continuous production of 99.6-99.8 wt%-pure, sub-millimeter-long, few-wall CNTs with an average diameter of 6.5 nm at a carbon yield of 42%. The FBCVD reactor with an internal heat-exchanger can be scaled-up for practical mass production with uniform and energy-saving heating. (C) 2014 Elsevier Ltd. All rights reserved.

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    40
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  • One-Step Sub-10 mu m patterning of Carbon-Nanotube Thin Films for Transparent Conductor Applications

    Norihiro Fukaya, Dong Young Kim, Shigeru Kishimoto, Suguru Noda, Yutaka Ohno

    ACS NANO   8 ( 4 ) 3285 - 3293  2014.04  [Refereed]

     View Summary

    We propose a technique for one-step micropatterning of as-grown carbon-nanotube films on a plastic substrate with sub-10 mu m resolution on the basis of the dry transfer process. By utilizing this technique, we demonstrated the novel high-performance flexible carbon-nanotube transparent conductive film with a microgrid structure, which enabled improvement of the performance over the trade-off between the sheet resistance and transmittance of a conventional uniform carbon-nanotube film. The sheet resistance was reduced by 46% at its maximum by adding the microgrid, leading to a value of 53 Omega/sq at a transmittance of 80%. We also demonstrated easy fabrication of multitouch projected capacitive sensors with 12 x 12 electrodes. The technique is quite promising for energy-saving production of transparent conductor devices with 100% material utilization.

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    75
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  • Carbon nanotube 3D current collectors for lightweight, high performance and low cost supercapacitor electrodes

    Ricardo Quintero, Dong Young Kim, Kei Hasegawa, Yuki Yamada, Atsuo Yamada, Suguru Noda

    RSC ADVANCES   4 ( 16 ) 8230 - 8237  2014  [Refereed]

     View Summary

    Self-supporting hybrid electrodes were fabricated through the systematic combination of activated carbon (AC), a low cost capacitive material, with sub-millimetre long few-wall carbon nanotubes (FWCNTs). After an easy three-step (mixing, dispersion and filtration) process, robust self-supporting films were obtained, comprising 90% AC particles wrapped in a 3-dimensional FWCNT collector. The 10% FWCNTs provide electrical conductivity and mechanical strength, and replace heavier metal collectors. The FWCNT matrix effectively improved the capacitance of the inexpensive, high surface area AC to 169 F g(-1) at a slow scan rate of 5 mV s(-1), and to 131 F g(-1) at a fast scan rate of 100 mV s(-1), in fairly thick (similar to 200 mu m) electrodes. Connection to a metallic collector at the film edge only, which significantly reduced the use of metal, retained much larger capacitance for the AC-FWCNT hybrid film (107 F g(-1)) than for the conventional AC electrode with binder and conductive filler (3.9 F g(-1)) at a practical voltage scan rate, 100 mV s(-1). Transport measurements in three-and two-electrode cells show that the FWCNT matrix can greatly enhance the conductivity of the AC-based films.

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    35
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  • Methane-Assisted Chemical Vapor Deposition Yielding Millimeter-Tall Single-Wall Carbon Nanotubes of Smaller Diameter

    Zhongming Chen, Dong Young Kim, Kei Hasegawa, Suguru Noda

    ACS NANO   7 ( 8 ) 6719 - 6728  2013.08  [Refereed]

     View Summary

    We examined the use of low purity H-2 (96 vol % H-2 with 4 vol % CH4) in chemical vapor deposition (CVD) using a C2H2 feedstock, and obtained vertically aligned single-wall carbon nanotubes (VA-SWCNTs) with unexpectedly smaller diameters, larger height, and higher quality compared with those grown using pure H-2. During the catalyst annealing, carbon deposited at a small amount from CH4 on the Fe particles, which kept them small and dense. During CVD, CH4 prevented the Fe particles from coarsening, resulting in an enhanced growth lifetime and suppressed diameter increase of growing SWCNTs. These effects were observed only for CH4, and not for C2H4 or C2H2. (H-4-assisted CVD is an efficient and practical method that uses H-2 containing CH4 that is available as a byproduct in chemical factories.

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    25
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  • The effect of atmospheric tarnishing on the optical and structural properties of silver nanoparticles

    T W H Oates, M Losurdo, S Noda, K Hinrichs

    Journal of Physics D: Applied Physics   46 ( 14 ) 145308 - 145308  2013.03  [Refereed]

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    42
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  • Cold-gas chemical vapor deposition to identify the key precursor for rapidly growing vertically-aligned single-wall and few-wall carbon nanotubes from pyrolyzed ethanol

    Hisashi Sugime, Suguru Noda

    CARBON   50 ( 8 ) 2953 - 2960  2012.07  [Refereed]

     View Summary

    Vertically-aligned carbon nanotubes (VA-CNTs) were rapidly grown from ethanol and their chemistry has been studied using a "cold-gas" chemical vapor deposition (CVD) method. Ethanol vapor was preheated in a furnace, cooled down and then flowed over cobalt catalysts upon ribbon-shaped substrates at 800 degrees C, while keeping the gas unheated. CNTs were obtained from ethanol on a sub-micrometer scale without preheating, but on a millimeter scale with preheating at 1000 degrees C. Acetylene was predicted to be the direct precursor by gas chromatography and gas-phase kinetic simulation, and actually led to millimeter-tall VA-CNTs without preheating when fed with hydrogen and water. There was, however a difference in CNT structure, i.e. mainly few-wall tubes from pyrolyzed ethanol and mainly single-wall tubes for unheated acetylene, and the by-products from ethanol pyrolysis possibly caused this difference. The "cold-gas" CVD, in which the gas-phase and catalytic reactions are separately controlled, allowed us to further understand CNT growth. (C) 2012 Elsevier Ltd. All rights reserved.

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    31
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  • One second growth of carbon nanotube arrays on a glass substrate by pulsed-current heating

    Kotaro Sekiguchi, Koji Furuichi, Yosuke Shiratori, Suguru Noda

    CARBON   50 ( 6 ) 2110 - 2118  2012.05  [Refereed]

     View Summary

    We report the very rapid growth of carbon nanotubes (CNTs) at high temperatures that can be tolerated by glass substrates. Glass substrates with metal microelectrodes and sputtered catalysts are heated by a pulsed current in a chemical vapour deposition gas environment for 0.5-1 s to synthesize CNTs of several micrometres in height without damaging the glass substrate. CNTs with structures from single-walled to multi-walled and morphologies from entangled networks to vertically aligned forests are grown simply by changing the nominal thickness of the catalyst, and such CNTs grown selectively on the microelectrodes worked as field emitters for cathodoluminescence. Rapid, easy growth of patterned CNT arrays on glass substrates without using furnaces/heaters or vacuum pumps will be useful for various applications of CNTs. (C) 2012 Elsevier Ltd. All rights reserved.

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    9
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  • Fluidized-bed synthesis of sub-millimeter-long single walled carbon nanotube arrays

    Dong Young Kim, Hisashi Sugime, Kei Hasegawa, Toshio Osawa, Suguru Noda

    CARBON   50 ( 4 ) 1538 - 1545  2012.04  [Refereed]

     View Summary

    The rapid growth method for vertically aligned, single walled carbon nanotube (SWCNT) arrays on flat substrates was applied to a fluidized-bed, using ceramic beads as catalyst supports as a means to mass produce sub-millimeter-long SWCNT arrays. Fe/Al2Ox catalysts were deposited on the surface of Al2O3 beads by sputtering and SWCNTs were grown on the beads by chemical vapor deposition (CVD) using C2H2 as a feedstock. Scanning electron microscopy and transmission electron microscopy showed that SWCNTs of 2-4 nm in diameter grew and formed vertically aligned arrays of 0.5 mm in height. Thermogravimetric analysis showed that the SWCNTs had a catalyst impurity level below 1 wt.%. Furthermore, they were synthesized at a carbon yield as high as 65 at.% with a gas residence time as short as &lt;0.2 s. Our fluidized-bed CVD, which efficiently utilizes the three-dimensional space of the reactor volume while retaining the characteristics of SWCNTs on substrates, is a promising option for mass-production of high-purity, sub-millimeter-long SWCNT arrays. (C) 2011 Elsevier Ltd. All rights reserved.

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    38
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  • Composite of TiN Nanoparticles and Few-Walled Carbon Nanotubes and Its Application to the Electrocatalytic Oxygen Reduction Reaction

    Shunsuke Isogai, Ryohji Ohnishi, Masao Katayama, Jun Kubota, Dong Young Kim, Suguru Noda, Dongkyu Cha, Kazuhiro Takanabe, Kazunari Domen

    CHEMISTRY-AN ASIAN JOURNAL   7 ( 2 ) 286 - 289  2012.02  [Refereed]

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    32
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  • Self-standing positive electrodes of oxidized few-walled carbon nanotubes for light-weight and high-power lithium batteries

    Seung Woo Lee, Betar M. Gallant, Youngmin Lee, Noboru Yoshida, Dong Young Kim, Yuki Yamada, Suguru Noda, Atsuo Yamada, Yang Shao-Horn

    ENERGY & ENVIRONMENTAL SCIENCE   5 ( 1 ) 5437 - 5444  2012.01  [Refereed]

     View Summary

    Binder-free and self-standing carbon nanotube (CNT) electrodes of tens of microns in thickness have been assembled via a vacuum-filtration process of oxidized few-walled CNTs (FWNTs), with different amounts of oxygen functional groups on FWNTs. Sub-millimetre long FWNTs can provide high electrical conductivity and mechanical strength in self-standing porous networks by reducing the number of junctions among FWNTs. We show that the gravimetric capacity of FWNT electrodes in lithium cells can be enhanced by increasing oxygen functional groups on FWNTs, which results from Faradaic reactions between lithium ions and surface oxygen functional groups. These self-standing FWNT electrodes (free of binder/additive and current collector) can provide a high gravimetric energy of similar to 200 W h kg(-1) at a high power of similar to 10 kW kg(-1), showing promise as the positive electrode for lightweight, high-power lithium batteries.

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  • Zeolite Surface As a Catalyst Support Material for Synthesis of Single-Walled Carbon Nanotubes

    Takahiko Moteki, Yoichi Murakami, Suguru Noda, Shigeo Maruyama, Tatsuya Okubo

    JOURNAL OF PHYSICAL CHEMISTRY C   115 ( 49 ) 24231 - 24237  2011.12  [Refereed]

     View Summary

    Preparation of single-walled carbon nanotubes (SWNTs) has been advanced by controlling several parameters including the catalyst and the catalyst support material. Although zeolite has been frequently used as a catalyst support material for the synthesis of SWNTs, detailed surface properties of previously employed zeolites and thus their role as a catalyst support material have not been sufficiently clarified yet. In this study, a clean b-plane surface of silicalite-1, which is a siliceous MEI-type zeolite, was used as a model substrate for the synthesis of SWNTs. The amount of active cobalt used for SWNT generation was smaller than the initially sputtered amount, and XPS measurements revealed diffusion of cobalt into the zeolite framework. The diffused cobalt was found to interact strongly with the silica framework of zeolite. The diffusion coefficient of cobalt in silicalite-1 zeolite was larger than that in thermally oxidized SiO2 formed on a Si substrate. This difference was ascribed to the microporous structure and lower density of zeolite. In this study, the state of the cobalt catalyst and the interaction between cobalt and the crystalline zeolite substrate is presented and discussed.

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    17
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  • Moderating carbon supply and suppressing Ostwald ripening of catalyst particles to produce 4.5-mm-tall single-walled carbon nanotube forests

    Kei Hasegawa, Suguru Noda

    CARBON   49 ( 13 ) 4497 - 4504  2011.11  [Refereed]

     View Summary

    Millimeter-tall single-walled carbon nanotube (SWCNT) forests were grown by chemical vapor deposition (CVD) from C2H2/H2O/Ar using Fe/Al-Si-O catalysts. Using combinatorial catalyst libraries coupled with real-time monitoring of SWCNT growth, the catalyst and CVD conditions were systematically studied. The keys for this growth are to maintain the C2H2 pressure below its upper limit to prevent the killing of the catalysts and to grow the SWCNTs before the catalyst particles lose their activity because of coarsening through Ostwald ripening. Lower temperatures lead to lower limits for the C2H2 pressure which result in lower growth rates but also lead to even lower coarsening rates which result in even longer growth lifetimes. Using these principles, we grew 4.5-mm-tall SWCNT forests in 2.5 h at 750 degrees C. (C) 2011 Elsevier Ltd. All rights reserved.

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    63
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  • Tailoring the Morphology of Carbon Nanotube Assemblies Using Microgradients in the Catalyst Thickness

    Yosuke Shiratori, Koji Furuichi, Yoshiko Tsuji, Hisashi Sugime, Suguru Noda

    JAPANESE JOURNAL OF APPLIED PHYSICS   50 ( 9 ) 095101  2011.09  [Refereed]

     View Summary

    In addition to the structural control of individual carbon nanotubes (CNTs), the morphological control of their assemblies is crucial to realize miniaturized CNT devices. Microgradients in the thickness of catalyst are used to enrich the variety of available self-organized morphologies of CNTs. Microtrenches were fabricated in gate/spacer/cathode trilayers using a conventional self-aligned top-down process and catalyst exhibiting a microgradient in its thickness was formed on the cathode by sputter deposition through gate slits. CNTs, including single-walled CNTs, of up to 1 mu m in length were grown within 5-15 s by chemical vapor deposition. The tendency of thin CNTs to aggregate caused interactions between CNTs with different growth rates, yielding various morphologies dependent on the thickness of the catalyst. The field emission properties of several types of CNT assemblies were evaluated. The ability to produce CNTs with tailored morphologies by engineering the spatial distribution of catalysts will enhance their performance in devices. (C) 2011 The Japan Society of Applied Physics

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  • A simple and fast method to disperse long single-walled carbon nanotubes introducing few defects

    Tatsuhiro Yamamoto, Suguru Noda, Masaru Kato

    CARBON   49 ( 10 ) 3179 - 3183  2011.08  [Refereed]

     View Summary

    A simple and fast dispersion method that incorporates heating is used to disperse long (more than 10 AM) single-walled carbon nanotubes (SWCNTs) with minimal defects. The method enables a dispersed solution of SWCNTs to be produced in less than 10 min in only three steps: (1) addition of the dispersant, (2) heating, and (3) grinding. The dispersion method does not require sonication, which shortens the SWCNTs and can generate surface defects. SWCNT films were prepared from the dispersed solution, and the films exhibited a resistance of 380 Omega/sq at a transparency of 64.8%. This dispersion method can be easily scaled up, making it useful for the preparation of dispersed SWCNTs for commercial and industrial applications. (C) 2011 Elsevier Ltd. All rights reserved.

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    17
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  • Sub-millimeter-long carbon nanotubes repeatedly grown on and separated from ceramic beads in a single fluidized bed reactor

    Dong Young Kim, Hisashi Sugime, Kei Hasegawa, Toshio Osawa, Suguru Noda

    CARBON   49 ( 6 ) 1972 - 1979  2011.05  [Refereed]

     View Summary

    A semi-continuous fluidized-bed process is reported which rapidly converts acetylene into carbon nanotubes (CNTs). Catalysts are first immobilized on ceramic beads and CNTs are then grown on the beads and then separated from them in a repetitive process accomplished within a single reactor simply by switching gases at a fixed temperature. CNTs of 6-10 nm diameter, three walls on average, 0.4 mm length and 99 wt.% purity were synthesized at an yield of over 70% in a reactor residence time shorter than 0.3 s. The easy and efficient production of such CNTs with in situ separation from the catalysts may accelerate the development of CNT-based nanotechnology industries. (C) 2011 Elsevier Ltd. All rights reserved.

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    69
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  • Nanostructure and magnetic properties of c-axis oriented L1(0)-FePt nanoparticles and nanocrystalline films on polycrystalline TiN underlayers

    Yoshiko Tsuji, Suguru Noda, Shinichi Nakamura

    JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B   29 ( 3 ) 031801  2011.05  [Refereed]

     View Summary

    We performed a systematic study of the nanostructure and magnetic properties of FePt on templates of either (200)-oriented polycrystalline TiN underlayers with in-plane grain sizes from 5.8 to 10 nm (poly-TiN) or highly (200)-textured TiN underlayers epitaxially grown on single-crystalline MgO (100) substrates (epi-TiN). For small nominal FePt thicknesses (0.7-8.0 nm), FePt forms particulate films with the magnetic easy axis perpendicular to the film plane on every template TiN underlayer. In addition, the coercivity of nominally 1.4-nm-thick FePt at 300 K in the out-of-plane direction increases from 5.3 kOe for 5.8-nm-sized poly-TiN to 12.9 kOe for 10-nm-sized poly-TiN and reaches 16.3 kOe for epi-TiN, which shows that the coercivity strongly depends on the degree of the c-axis orientation. For larger FePt nominal thicknesses (16-64 nm), FePt particles percolate and form continuous films, and the direction of the easy magnetic easy axis becomes random. The coercivity of nominally 64-nm-thick FePt at 300 K in the out-of-plane direction is still as large as 8.8 kOe for 10-nm-sized poly-TiN, but it drastically decreases to 0.5 kOe for epi-TiN. The absence of in-plane texture in the FePt layer on the poly-TiN suppresses the decrease in coercivity, which prevents domain-wall displacement. (C) 2011 American Vacuum Society. [DOI: 10.1116/1.3575155]

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  • Millimeter-Tall Single-Walled Carbon Nanotubes Rapidly Grown with and without Water

    Kei Hasegawa, Suguru Noda

    ACS NANO   5 ( 2 ) 975 - 984  2011.02  [Refereed]

     View Summary

    Millimeter-tall vertically aligned single-walled carbon nanotubes (SWCNTs) were grown in 10-15 min by chemical vapor deposition from C(2)H(2)/Ar with or without water addition using Fe catalyst supported on an Al-Si-O underlayer. Using combinatorial catalyst libraries coupled with the real-time monitoring of SWCNT growth, the catalyst and chemical vapor deposition conditions were systematically examined, and millimeter-tall SWCNTs were obtained even without water addition. The key for millimeter-scale growth of SWCNTs is to limit the C(2)H(2) supply to below a certain partial pressure to retain an active catalyst. Water prolongs the catalyst lifetime under excess C(2)H(2) supply, whereas it deactivates small catalyst particles and degrades the quality of SWCNTs at the same time. We also observed a gradual increase in the diameter of SWCNTs with growth because of the coarsening of catalyst particles and found that water had no effect on this phenomenon. We demonstrate millimeter-tall SWCNTs grown by simply using C(2)H(2)/Ar gas without water addition, which revealed the mysterious role of water, and we show a practical route for the large-scale production of SWCNTs.

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    108
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  • Two routes to polycrystalline CoSi2 thin films by co-sputtering Co and Si

    Yukie Tsuji, Yoshiko Tsuji, Shinichi Nakamura, Suguru Noda

    APPLIED SURFACE SCIENCE   256 ( 23 ) 7118 - 7124  2010.09  [Refereed]

     View Summary

    Two processes for the fabrication of polycrystalline CoSi2 thin films based on the codeposition of Co and Si by sputtering were studied and compared. The first process involved "annealing after deposition", where Co and Si are codeposited at ambient temperature and then crystallized by annealing. This process yielded randomly oriented plate-like CoSi2 grains with a grain size that is governed by the nanostructure of the as-deposited film. Polycrystalline CoSi2 thin films were obtained at a process temperature of 170 degrees C, which was much lower than the annealing temperature of 500 degrees C needed for Co/Si bilayers. The second process involved "heating during deposition", where Co and Si are codeposited on heated substrates. This process yielded CoSi2 grains with a columnar structure, and the grain size and degree of (1 1 1) orientation are temperature dependent. The sheet resistance of the resulting films was determined by the preparation temperature regardless of the deposition process used, i.e. "annealing after deposition" or "heating during deposition". Temperatures of 500 degrees C and higher were needed to achieve CoSi2 resistivity of 40 mu Omega cm or lower for both processes. (C) 2010 Elsevier B.V. All rights reserved.

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  • Combinatorial Evaluation for Field Emission Properties of Carbon Nanotubes Part II: High Growth Rate System

    Yosuke Shiratori, Suguru Noda

    JOURNAL OF PHYSICAL CHEMISTRY C   114 ( 30 ) 12938 - 12947  2010.08  [Refereed]

     View Summary

    Carbon nanotube (CNT) emitters are of interest for inclusion in cold cathodes and field emission displays. CNT field electron emitters self-organized on substrates with an Fe/Al2O3 catalytic/supporting layer, which accelerates CNT growth, are characterized using combinatorial libraries. A variety of morphologies are formed on single substrates by C2H2 thermal chemical vapor deposition for 10 s at ambient pressure. Degradation of field emission decreases upon prolonged operation. Raman signals from thinner single-walled CNTs predominantly degrade during operation. Controlling the number of protruding thin CNTs is crucial to extracting current and ensuring sustainability. Thin CNTs protruding from CNT ensembles formed on a substrate with a multimodal distribution of catalyst particles show good field emission (FE) properties with practical sustainability. A potential design for self-organized thin CNTs fabricated by the current process is discussed on the basis of the combinatorial evaluation for field emission and 3D electric field simulations.

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    4
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  • Real-Time Monitoring of Millimeter-Tall Vertically Aligned Single-Walled Carbon Nanotube Growth on Combinatorial Catalyst Library

    Kei Hasegawa, Suguru Noda

    JAPANESE JOURNAL OF APPLIED PHYSICS   49 ( 8 ) 085104  2010.08  [Refereed]

     View Summary

    The rapid growth dynamics of millimeter-tall, vertically aligned single-walled carbon nanotubes (VA-SWCNTs) was studied using a simple real-time monitoring method By using combinatorial catalyst libraries, VA-SWCNT growth curves under various catalyst conditions were obtained in a single chemical vapor deposition (CVD) run VA-SWCNTs grew at constant or gradually decreasing rates for several minutes and then abruptly ceased growth This unusual behavior of the growth occurred under wide ranges of catalyst and CVD conditions (C) 2010 The Japan Society of Applied Physics

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  • Millimeter-tall single-walled carbon nanotube forests grown from ethanol

    Hisashi Sugime, Suguru Noda

    CARBON   48 ( 8 ) 2203 - 2211  2010.07  [Refereed]

     View Summary

    Millimeter-tall vertically-aligned carbon nanotubes (VA-CNTs) were grown from ethanol under ambient pressure by Co-catalyzed chemical vapor deposition (CVD), with systematic optimization of the CVD temperature and catalytic conditions using combinatorial catalyst libraries. We investigated the use of both aluminum oxide and silicon oxide as underlayers for the Co catalyst and found that VA-CNTs grew to millimeter heights in 15-30 min when the pyrolysis of ethanol was carried out at high temperatures (2-850 degrees C) and long residence times (&gt;= 10 s). Thick Co catalytic layers (&gt;= 1.3 nm) produced (sub)millimeter-tall multi-walled VA-CNTs on both the aluminum oxide and silicon oxide underlayers. However, thin Co catalytic layers (0.62-1.0 nm) produced (sub)millimeter-tall VA-CNTs, which consisted mainly of single-walled CNTs, only on the aluminum oxide underlayers. Stripe patterns were found in the VA-CNTs near the substrate on both aluminum oxide and silicon oxide, indicating some instability prior to growth termination. The possible roles of aluminum oxide in growing millimeter-tall single-walled VA-CNTs were discussed. (C) 2010 Elsevier Ltd. All rights reserved.

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  • A Simple Combinatorial Method Aiding Research on Single-Walled Carbon Nanotube Growth on Substrates

    Suguru Noda, Hisashi Sugime, Kei Hasegawa, Kazunori Kakehi, Yosuke Shiratori

    JAPANESE JOURNAL OF APPLIED PHYSICS   49 ( 2 ) 02BA02  2010  [Refereed]

     View Summary

    Establishing fabrication methods of carbon nanotubes (CNTs) is essential to realize many applications expected for CNTs. Catalytic growth of CNTs on substrates by chemical vapor deposition (CVD) is promising for direct fabrication of CNT devices, and catalyst nanoparticles play a crucial role in such growth. We have developed a simple method called "combinatorial masked deposition (CMD)'', in which catalyst particles of a given series of sizes and compositions are formed on a single substrate by annealing gradient catalyst layers formed by sputtering through a mask. CMD enables preparation of hundreds of catalysts on a wafer, growth of single-walled CNTs (SWCNTs), and evaluation of SWCNT diameter distributions by automated Raman mapping in a single day. CMD helps determinations of the CVD and catalyst windows realizing millimeter-tall SWCNT forest growth in 10 min, and of growth curves for a series of catalysts in a single measurement when combined with real-time monitoring. A catalyst library prepared using CMD yields various CNTs, ranging from individuals, networks, spikes, and to forests of both SWCNTs and multi-walled CNTs, and thus can be used to efficiently evaluate self-organized CNT field emitters, for example. The CMD method is simple yet effective for research of CNT growth methods. (C) 2010 The Japan Society of Applied Physics

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    22
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  • Diameter Increase in Millimeter-Tall Vertically Aligned Single-Walled Carbon Nanotubes during Growth

    Kei Hasegawa, Suguru Noda

    APPLIED PHYSICS EXPRESS   3 ( 4 ) 045103  2010  [Refereed]

     View Summary

    Diameter increase was found during the rapid, vertically aligned growth of millimeter-long single-walled carbon nanotubes (SWCNTs). The diameters continuously increased on average from 1.7nm at the top to 3.7nm at the bottom of vertically aligned SWCNTs. The SWCNT structures ranged from straight and bundled at the top to bent and isolated and even collapsed at the bottom. Our findings show the importance of suppressing catalyst coarsening to obtain thin SWCNTs, as well as a potential production route of thick SWCNTs and edgeless bilayer graphene ribbons. (C) 2010 The Japan Society of Applied Physics

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  • Efficient field emission from triode-type 1D arrays of carbon nanotubes

    Yosuke Shiratori, Koji Furuichi, Yoshiko Tsuji, Hisashi Sugime, Suguru Noda

    NANOTECHNOLOGY   20 ( 47 ) 475707  2009.11  [Refereed]

     View Summary

    Carbon nanotube (CNT) emitters were formed on line-patterned cathodes in microtrenches through a thermal CVD process. Single-walled carbon nanotubes (SWCNTs) self-organized along the trench lines with a submicron inter-CNT spacing. Excellent field emission (FE) properties were obtained: current densities at the anode (J(a)) of 1 mu A cm(-2), 10mA cm(-2) and 100 mA cm(-2) were recorded at gate voltages (V(g)) of 16, 25 and 36 V, respectively. The required voltage difference to gain a 1: 10 000 contrast of the anode current was as low as 9 V, indicating that a very low operating voltage is possible for these devices. Not only a large number of emission sites but also the optimal combination of trench structure and emitter morphology are crucial to achieve the full FE potential of thin CNTs with a practical lifetime. The FE properties of 1D arrays of CNT emitters and their optimal design are discussed. Self-organization of thin CNTs is an attractive prospect to tailor preferable emitter designs in FE devices.

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    8
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  • Two-Dimensional Combinatorial Investigation of Raman and Fluorescence Enhancement in Silver and Gold Sandwich Substrates

    T. W. H. Oates, Y. Shiratori, S. Noda

    JOURNAL OF PHYSICAL CHEMISTRY C   113 ( 22 ) 9588 - 9594  2009.06  [Refereed]

     View Summary

    We present a two-dimensional combinatorial investigation of resonant Raman and fluorescence enhancement in silver and gold sandwich structures. Gold and silver, separated by a thin alumina spacer layer, were deposited in two orthogonal gradients, with a thickness from a few hundred to a few nanometers, covering the range from island films through percolation to continuous films. Resonant Raman spectra of Rhodamine 6G adsorbed on the substrate surface were recorded in a 13 x 13 matrix using an automated scanning stage. The most Raman-active substrates were composed of silver (8 nm)-on-alumina (7 nm)-on-gold (5 nm). They consist of both gold and silver discontinuous nanoparticle films separated by alumina, forming a labyrinthine network structure. Gold-on-alumina-on-silver substrates also displayed increased activity compared with that of goldon-alumina substrates. Maximum fluorescence intensity was observed on silver films nominally 35 nm thick covered by 8 nm of alumina. The efficacy of the combinatorial method to correlate multiple aspects of the measurements and reduce uncertainties is demonstrated.

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    7
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  • Combinatorial Surface-Enhanced Raman Spectroscopy and Spectroscopic Ellipsometry of Silver Island Films

    T. W. H. Oates, H. Sugime, S. Noda

    JOURNAL OF PHYSICAL CHEMISTRY C   113 ( 12 ) 4820 - 4828  2009.03  [Refereed]

     View Summary

    Utilizing a combinatorial method, we used spectroscopic ellipsometry to determine the dielectric functions of silver island films over a large range of sizes and morphologies from the percolation threshold down to average particle size smaller than 5 nm. We measured films on silicon substrates with 2 and 20 nm oxide layers and compared the surface-enhanced Raman scattering properties of the films. As expected, the films on 20-nm-thick oxide substrates showed increased Raman counts due to reduced damping of the plasmon resonance; however, the optical absorption was greater in the films on 2 nm oxide. The maximum Raman scattering was observed for average particle diameters of 13.6 and 25 nm and interparticle spacings of 3.3 and 4.1 nm for the 2 and 20 nm oxide substrates, respectively. The use of a combinatorial method resulted in significantly reduced uncertainties by avoiding multiple sample preparations and allowed unambiguous identification of optimal film parameters for the different substrates.

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  • Thickness-gradient dependent Raman enhancement in silver island films

    T. W. H. Oates, S. Noda

    APPLIED PHYSICS LETTERS   94 ( 5 ) 053106  2009.02  [Refereed]

     View Summary

    We show evidence of a dependence of the enhancement of the Raman scattering cross section on the length of the gradient in graded silver island films. A factor-of-three increase in the Raman signal is observed for gradients with length of the order of 0.5 mm when compared to gradients of the order of 9 mm. Scanning electron microscopy reveals the nanostructure of the two films to be statistically similar. We attribute the observation to differences in plasmon hybridization in the gradients arising from long range structural differences.

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    17
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  • 流動層による単層カーボンナノチューブの合成

    金 東榮, 深井 尋史, 杉目 恒志, 長谷川 馨, 大沢 利男, 野田 優

    化学工学会 研究発表講演要旨集   2009   12 - 12  2009

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  • 1-Second Implementation of CNT-Emitter Arrays on Glasses for BLUs

    Koji Furuichi, Yosuke Shiratori, Kotaro Sekiguchi, Hisashi Sugime, Suguru Noda

    2009 SID INTERNATIONAL SYMPOSIUM DIGEST OF TECHNICAL PAPERS, VOL XL, BOOKS I - III     139 - +  2009  [Refereed]

     View Summary

    We realized simple fabrication of carbon nanotube field emitters for backlight units. Carbon nanotubes were directly grown on cathode lines patterned on low-strain glasses by atmospheric pressure CVD with pulse electrical heating of cathodes for I second. Field emission current density was as high as 5.6 mA/cm(2) at 3.3 V/mu m.

  • Chemical Engineering for Technology Innovation

    Yukio Yamauchi, Suguru Noda, Hiroshi Komiyama

    CHEMICAL ENGINEERING COMMUNICATIONS   196 ( 1-2 ) 267 - 276  2009  [Refereed]

     View Summary

    Sustainability of human beings in the 21st century requires development of renewable energy systems based on technology innovation. Chemical engineering plays a key role in promoting technology innovation relating to environmental and energy systems. The technological domains to which chemical engineering has contributed have shift from petrochemicals to functional materials and devices. An example of the key devices expected in the future is a combination of solar cells and Li-ion batteries, in which the indispensable materials are silicon and carbon. The shape and nanostructure of materials must be controlled to fabricate highly efficient devices at a low cost. Single-walled carbon nanotubes (SWNT) and spherical silicon solar cells (SSSC) with a semi-concentration reflector system are discussed as examples of future materials and devices. Chemical engineering is responsible for technology innovation through mass production, product quality control, materials recycling, high-quality device fabrication, and structuring knowledge.

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    2
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  • Multiple "optimum" conditions for Co-Mo catalyzed growth of vertically aligned single-walled carbon nanotube forests

    Hisashi Sugime, Suguru Noda, Shigeo Maruyama, Yukio Yamaguchi

    CARBON   47 ( 1 ) 234 - 241  2009.01  [Refereed]

     View Summary

    Carbon nanotubes (CNTs) were grown directly on substrates by alcohol catalytic chemical vapor deposition using a Co-Mo binary catalyst. Optimum catalytic and reaction conditions were investigated using a combinatorial catalyst library. High catalytic activity areas on the substrate were identified by mapping the CNT yield against the orthogonal gradient thickness profiles of Co and Mo. The location of these areas shifted with changes in reaction temperature, ethanol pressure and ethanol flow rate. Vertically aligned single-walled CNT (SWCNT) forests grew in several areas to a maximum height of ca. 30 mu m in 10 min. A pure Co catalyst yielded a vertically aligned SWCNT forest with a bimodal diameter distribution. The effects of Mo on the formation of catalyst nanoparticles and on the diameter distribution of SWCNTs are discussed and Mo as thin as a monolayer or thinner was found to suppress the broadening of SWCNT diameter distributions. (C) 2008 Elsevier Ltd. All rights reserved.

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  • Growth Window and Possible Mechanism of Millimeter-Thick Single-Walled Carbon Nanotube Forests

    Kei Hasegawa, Suguru Noda, Hisashi Sugime, Kazunori Kakehi, Shigeo Maruyama, Yukio Yamaguchi

    JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY   8 ( 11 ) 6123 - 6128  2008.11  [Refereed]

     View Summary

    Our group recently reproduced the water-assisted growth method, so-called "SuperGrowth," of millimeter-thick single-walled carbon nanotube (SWNT) forests by using C2H4/H-2/H2O/Ar reactant gas and Fe/Al2O3 catalyst. In this current work, a parametric study was carried out on both reaction and catalyst conditions. Results revealed that a thin Fe catalyst layer (about 0.5 nm) yielded rapid growth of SWNTs only when supported on Al2O3, and that Al2O3 support enhanced the activity of Fe, Co, and Ni catalysts. The growth window for the rapid SWNT growth was narrow, however. Optimum amount of added H2O increased the SWNT growth rate but further addition of H2O degraded both the SWNT growth rate and quality Addition of H-2 was also essential for rapid SWNT growth, but again, further addition decreased both the SWNT growth rate and quality. Because Al2O3 catalyzes hydrocarbon reforming, Al2O3 support possibly enhances the SWNT growth rate by supplying the carbon source to the catalyst nanoparticles. The origin of the narrow window for rapid SWNT growth is also discussed.

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    38
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  • Combinatorial Evaluation for Field Emission Properties of Carbon Nanotubes

    Yosuke Shiratori, Hisashi Sugime, Suguru Noda

    JOURNAL OF PHYSICAL CHEMISTRY C   112 ( 46 ) 17974 - 17982  2008.11  [Refereed]

     View Summary

    Field emission properties of carbon nanotubes (CNTs) were comparatively evaluated by using combinatorial CNT libraries. The libraries were prepared by combinatorial masked deposition of a Co catalytic layer on Al2O3/Si substrates and subsequent CNT growth by chemical vapor deposition from ethanol. Each library reproduced various types of single- and multiwalled carbon nanotubes with different morphologies and a variety of field emission properties. Combinatorial evaluations immediately identified the CNTs preferable as field emitters. The results obtained from individual field emission evaluations for samples with a constant nominal Co thickness agreed well with the results obtained from comparative evaluations for combinatorial CNT libraries. The results revealed that protrusive single-walled carbon nanotubes with a moderate interspacing showed the best field emission properties.

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    11
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  • Self-organized metallic nanoparticle and nanowire arrays from ion-sputtered silicon templates

    T. W. H. Oates, A. Keller, S. Noda, S. Facsko

    APPLIED PHYSICS LETTERS   93 ( 6 ) 063106  2008.08  [Refereed]

     View Summary

    We demonstrate a production method for self-organized arrays of metal nanoparticles and aligned nanowires. Ion beam-sputtered Si/SiO2 substrates are used as templates for metallic vapor deposition, forming aligned arrays of 5-20 nm silver and cobalt nanoparticles with a period of 35 nm. The 20 nm diameter cobalt nanowires with lengths in excess of a micrometer are produced under appropriate conditions. All processing steps can be integrated into a single vacuum chamber and performed in a matter of minutes at mild temperatures. This inherently scalable technique can be extended to a range of substrate materials, array patterns, and nanoparticle materials. (C) 2008 American Institute of Physics.

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  • Individuals, grasses, and forests of single- and multi-walled carbon nanotubes grown by supported Co catalysts of different nominal thicknesses

    Kazunori Kakehi, Suguru Noda, Shigeo Maruyama, Yukio Yamaguchi

    APPLIED SURFACE SCIENCE   254 ( 21 ) 6710 - 6714  2008.08  [Refereed]

     View Summary

    The relationships among the nominal thickness of Co catalyst, the structure of the catalyst particles, and the structure of carbon nanotubes (CNTs) growing from the catalyst during chemical vapor deposition were investigated. Various morphologies of CNTs such as individuals, random networks parallel to the surface of the substrate (&apos;grasses&apos;), and vertically aligned forests of single- and multi-walled carbon nanotubes were grown by only varying the nominal thickness of catalyst under the same reaction condition. These different morphologies at the same growth time were due to the different areal density rather than to the length of CNTs. With increasing nominal thickness of catalyst, the catalyst particles changed in diameter while their areal density remained relatively almost constant. The change in diameter possibly affected the number ratio of active catalyst particles to the whole particles, which in turn affected the areal density of CNTs and yielded the various morphologies. Longer growth time increased the CNT length, which caused further change in CNT morphologies from individuals to grasses and grasses to forests. (C) 2008 Elsevier B. V. All rights reserved.

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  • Field emission properties of single-walled carbon nanotubes with a variety of emitter morphologies

    Yosuke Shiratori, Koji Furuichi, Suguru Noda, Hisashi Sugime, Yoshiko Tsuji, Zhengyi Zhang, Shigeo Maruyama, Yukio Yamaguchi

    JAPANESE JOURNAL OF APPLIED PHYSICS   47 ( 6 ) 4780 - 4787  2008.06  [Refereed]

     View Summary

    Field emission properties of single-walled carbon nanotubes (SWCNTs), which were prepared through alcohol catalytic chemical vapor deposition for 10-60s, were characterized in a diode configuration. Protrusive bundles at the top surface of samples act selectively as emission sites. The number of emission sites was controlled by emitter morphologies combined with texturing of Si substrates. SWCNTs grown on a textured Si substrate exhibited a turn-on field as low as 2.4 V/mu m at a field emission current density of 1 mu A/cm(2). Uniform spatial luminescence (0.5 cm(2)) from the rear surface of the anode was revealed for SWCNTs prepared on the textured Si substrate. Deterioration of field emission properties through repetitive measurements was reduced for the textured samples in comparison with vertically aligned SWCNTs and a random network of SWCNTs prepared on flat Si substrates. Emitter morphology resulting in improved field emission properties is a crucial factor for the fabrication of SWCNT-electron sources. Morphologically controlled SWCNTs with promising emitter performance are expected to be practical electron sources.

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    16
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  • Growth mechanism of epitaxial CoSi2 on Si and reactive deposition epitaxy of double heteroepitaxial Si/CoSi2/Si

    Yoshiko Tsuji, Makoto Mizukami, Suguru Noda

    THIN SOLID FILMS   516 ( 12 ) 3989 - 3995  2008.04  [Refereed]

     View Summary

    The growth mechanism of epitaxial CoSi2 was studied using Co/Ti/Si multilayer solid phase reaction. Results showed that phase formation was controlled by diffusion of Co through the growing CoSix, although at the early stage of CoSi2 growth the diffusion of Co could be controlled by a Ti layer. A reactive deposition technique was also evaluated by using a conventional magnetron sputtering system. Results showed that an epitaxial CoSi2 layer was formed by controlling the Co sputtering rate not to exceed the Co diffusion rate through CoSix. However, the surface of CoSi2 became rough when the deposition rate was much slower than the Co diffusion rate through CoSix. The roughness was caused by the formation Of CoSi2 (111) facets at the interface between CoSi2 and the Si substrate. Si/CoSi2/Si double heteroepitaxial structures were fabricated when Si and Co were sequentially sputter-deposited on a Si (100) substrate. (c) 2007 Elsevier B.V. All rights reserved.

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    10
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  • Growth valley dividing single- and multi-walled carbon nanotubes: Combinatorial study of nominal thickness of Co catalyst

    Kazunori Kakehi, Suguru Noda, Shigeo Maruyama, Yukio Yamaguchi

    JAPANESE JOURNAL OF APPLIED PHYSICS   47 ( 4 ) 1961 - 1965  2008.04

     View Summary

    The relationships among the nominal thickness of Co catalysts, the structure of the catalyst particles, and the structure of carbon nanotubes (CNTs) growing from the catalysts were investigated. A gradient thickness profile of Co was prepared using a combinatorial method and then subjected to alcohol catalytic chemical vapor deposition at 700 degrees C. In the deposited sample, two active regions appeared on either side of an inactive region. In the active regions, mainly single-walled carbon nanotubes (SWNTs) or multi-walled carbon nanotubes (MWNTs) grew, depending on the nominal Co thickness (SWNTs grown at a Co thickness of about 0.1 nm, and MWNTs grown at a Co thickness of about 1.5 nm). However, neither SWNTs nor MWNTs grew efficiently at a moderate Co thickness (similar to 0.4 nm). This dependence of CNT growth on the initial Co thickness is explained by the different mechanisms of catalyst particle formation from sub-nanometer-thick and nanometer-thick Co films.

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    26
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  • 触媒CVD法における単層カーボンナノチューブ垂直配向成長の前駆体

    杉目 恒志, 野田 優, 山口 由岐夫

    化学工学会 研究発表講演要旨集   2008   783 - 783  2008

    DOI CiNii

  • 電子エミッタ応用を目的とした単層カーボンナノチューブの形態制御とコンビナトリアル特性評価

    白鳥 洋介, 古市 考次, 野田 優, 辻 佳子, 杉目 恒志, 張 正宜, 丸山 茂夫, 山口 由岐夫

    化学工学会 研究発表講演要旨集   2008   790 - 790  2008

    DOI CiNii

  • 自己組織化を利用した単層CNTフィールドエミッタの高密度集積

    野田 優, 古市 考次, 白鳥 洋介, 辻 佳子, 杉目 恒志, 山口 由岐夫

    化学工学会 研究発表講演要旨集   2008   791 - 791  2008

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  • カーボンナノチューブ成長の持続性と触媒粒子構造

    筧 和憲, 野田 優, 丸山 茂夫, 山口 由岐夫

    化学工学会 研究発表講演要旨集   2008   638 - 638  2008

    DOI CiNii

  • Structure and magnetic property of c-axis oriented L1(0)-FePt nanoparticles on TiN/a-Si underlayers

    Yoshiko Tsuji, Suguru Noda, Yukio Yamaguchi

    JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B   25 ( 6 ) 1892 - 1895  2007.11  [Refereed]

     View Summary

    L1(0)-FePt is a promising material for high-density perpendicular magnetic recording media. The authors previously reported that c-axis oriented L1(0)-FePt nanoparticle monolayers can be formed on (200)-oriented polycrystalline template TiN underlayers on SiO2 by using a conventional sputtering method. In this study, TiN nanostructures, such as the degree of (200) orientation, were improved by first depositing a buffer layer, such as amorphous Si onto SiO2, and the grain size could be controlled by adjusting either the deposition temperature or TiN thickness. When FePt nanoparticles were formed on a template TiN underlayer with a buffer layer of amorphous Si, both their degree of c-axis orientation and their magnetic properties were improved; FePt nanoparticles with nominal thickness of 1.4 nm had coercivity of 12.9 kOe in the out-of-plane direction at 300 K. (c) 2007 American Vacuum Society.

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  • Millimeter-thick single-walled carbon nanotube forests: Hidden role of catalyst support

    Suguru Noda, Kei Hasegawa, Hisashi Sugime, Kazunori Kakehi, Zhengyi Zhang, Shigeo Maruyama, Yukio Yamaguchi

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS & EXPRESS LETTERS   46 ( 17-19 ) L399 - L401  2007.05  [Refereed]

     View Summary

    A parametric study of so-called "super growth" of single-walled carbon nanotubes (SWNTs) was done by using combinatorial libraries of iron/aluminum oxide catalysts. Milli meter-thick forests of nanotubes grew within 10 min, and those grown by using catalysts with a thin Fe layer (about 0.5 nm) were SWNTs. Although nanotube forests grew under a wide range of reaction conditions such as gas composition and temperature, the window for SWNT was narrow. Fe catalysts rapidly grew nanotubes only when supported on aluminum oxide. Aluminum oxide, which is a well-known catalyst in hydrocarbon reforming, plays an essential role in enhancing the nanotube growth rates.

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  • Spontaneous formation of Si nanocones vertically aligned to Si wafers

    Yoshiko Tsuji, Shinichi Nakamura, Suguru Noda

    JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B   25 ( 3 ) 808 - 812  2007.05  [Refereed]

     View Summary

    A simple, practical method was developed to automatically align single crystalline Si nanocones (SiNCs) vertical to a Si substrate. Double heteroepitaxial structure of Si/CoSi2 on a Si (100) substrate was prepared by sputtering, and Si was then deposited on the surface via chemical vapor deposition with SiH2Cl2/H-2 reaction gas. When Si was deposited at 900 degrees C, SiNCs were fabricated vertical to the substrate, had a tip curvature of about 100 nm, and had a number density of (0.9-35) X 10(8)/m(2). A CoSi2 nanocrystal was clearly visible on the tip of each SiNC. These CoSi2 nanocrystals were formed by agglomeration of the Si/CoSi2 layer, and catalyzed the Si growth during chemical vapor deposition. In conclusion, the alignment of the fabricated SiNCs could be controlled by utilizing agglomeration in the Si/CoSi2/Si double heteroepitaxial structure. (c) 2007 American Vacuum Society.

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    2
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  • Fe/Al2O3触媒でのC2H4からのカーボンナノチューブ高速成長の条件とメカニズム

    長谷川 馨, 諸隈 慎吾, 伊藤 龍平, 杉目 恒志, 筧 和憲, 大沢 利男, 野田 優, 丸山 茂夫, 山口 由岐夫

    化学工学会 研究発表講演要旨集   2007   2 - 2  2007

    DOI CiNii

  • Supported Ni catalysts from nominal monolayer grow single-walled carbon nanotubes

    Kazunori Kakehi, Suguru Noda, Shohei Chiashi, Shigeo Maruyama

    CHEMICAL PHYSICS LETTERS   428 ( 4-6 ) 381 - 385  2006.09  [Refereed]

     View Summary

    Fe, Co, and Ni are catalytically effective for growing single-walled carbon nanotubes (SWNTs). On substrates, however, Ni tends to yield only multi-walled carbon nanotubes. Because enhanced surface diffusion at the elevated growth temperature required for deposition might cause coarsening of Ni catalyst nanoparticles, adjusting the nominal Ni thickness should be crucial for controlling the particle size. Using our previously developed combinatorial method, we prepared a thickness profile of Ni on a quartz glass (SiO(2)) substrate and found that Ni nanoparticles catalyzed the growth of SWNTs by chemical vapor deposition only when nominal Ni thickness was in the monolayer range. (c) 2006 Elsevier B.V. All rights reserved.

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  • A simple combinatorial method to discover Co-Mo binary catalysts that grow vertically aligned single-walled carbon nanotubes

    Suguru Noda, Hisashi Sugime, Toshio Osawa, Yoshiko Tsuji, Shohel Chiashi, Yoichi Murakami, Shigeo Maruyama

    CARBON   44 ( 8 ) 1414 - 1419  2006.07  [Refereed]

     View Summary

    A simple yet versatile combinatorial method to discover binary metal nanoparticle catalysts was developed. In this method, the nominal thickness of component metals can be independently screened for a wide range by simply setting a mask with a slit above a substrate during sputter-deposition. Using this method, we prepared a catalyst library with Mo (0.2-4 nm) and Co (0.2-8 nm) thickness profiles on a SiO(2)/Si wafer and discovered active catalysts that grow vertically aligned single-walled carbon nanotubes by alcohol catalytic chemical vapor deposition. (C) 2005 Elsevier Ltd. All rights reserved.

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  • Spectroscopic study of laser-induced phase transition of gold nanoparticles on nanosecond time scales and longer

    S Inasawa, M Sugiyama, S Noda, Y Yamaguchi

    JOURNAL OF PHYSICAL CHEMISTRY B   110 ( 7 ) 3114 - 3119  2006.02  [Refereed]

     View Summary

    The pulsed laser induced phase transition of gold nanoparticles in aqueous solution was observed via a transient absorption on nanosecond time scales and longer. Gold nanoparticles were excited with an intense picosecond laser pulse (355 nm, 30 ps), and the subsequent changes were monitored using two continuous wave laser wavelengths (488 and 635 nm). On the nanosecond time scale, below 6.3 mJ cm(-2), no change was observed; however, in the low fluence region between 6.3 and 17 mJ cm(-2), gold nanoparticles produced a bleach signal (488 nm) attributed to the melting of the gold nanoparticles, which decreased linearly with increasing laser fluence. Laser fluences above 17 mJ cm(-2) resulted in a strong absorption at both wavelengths, which is ascribed to vaporization of gold nanoparticles rather than solvated electrons (ejected from gold nanoparticles) or light scattering. The decay of both signals was faster than the 5 ns time resolution used in our experimental system. On the microsecond time scale, increase in absorbance at 635 nm was observed with a time constant of 1.0 mu s, while no change was observed at 488 nm. It is considered that this increase is attributed to the formation of smaller gold nanoparticles resulting from pulsed laser induced size reduction of initial gold nanoparticles.

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    68
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  • Novel analytical method of nanoparticle dispersibility in polymer nanocomposites; TEM-CT and 3D topological analysis

    Sasakura, H., Noda, S., Yamaguchi, Y.

    Journal of the Ceramic Society of Japan   114 ( 1331 )  2006  [Refereed]

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  • Filling the gap between researchers studying different materials and different methods: a proposal for structured keywords

    Yuya Kajikawa, Koji Abe, Suguru Noda

    JOURNAL OF INFORMATION SCIENCE   32 ( 6 ) 511 - 524  2006  [Refereed]

     View Summary

    Scientific publications written in natural language still play a central role as our knowledge source. However, due to the flood of publications, obtaining a comprehensive view even on a topic of limited scope, from a stack of publications is becoming an arduous task. Examples are presented from our recent experiences in the materials science field, where information is not shared among researchers studying different materials and different methods. To overcome the limitation, we propose a structured keywords method to reinforce the functionality of a future e-library.

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    31
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  • c-Axis oriented face-centered-tetragonal-fept nanoparticle monolayer formed on a polycrystalline TiN seed layer

    S Noda, Y Tsuji, A Sugiyama, A Kikitsu, F Okada, H Komiyama

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS BRIEF COMMUNICATIONS & REVIEW PAPERS   44 ( 11 ) 7957 - 7961  2005.11  [Refereed]

     View Summary

    c-Axis oriented face-centered-tetragonal (fct)-FePt magnetic nanoparticles are a promising candidate for. high density perpendicular magnetic recording media. In this study, TiN was investigated as a seed layer to achieve c-axis orientation of fct-FePt nanoparticles. First, a (200)-oriented, polycrystalline TiN layer with grain size around 10 nm was prepared by reactive sputter-deposition at 873 K on SiO(2), and then FePt was sputter-deposited at 973 K on it. Both in-plane and out-of-plane X-ray diffraction revealed that FePt had fct structure with c-axis orientation. Plan-view field emission scanning electron microscopy showed that FePt formed well-isolated nanoparticles. The particle diameter increased with increasing nominal thickness of FePt, and it was similar to the size of the TiN grains when nominal thickness was 1.4 nm. Cross-sectional transmission electron microscope images indicated that single FePt nanoparticles grew on single TiN grains, namely, one nanoparticle per grain, with an epitaxial relationship. Superconducting quantum inference device measurement at 300 K revealed that the FePt nanoparticles had coercivity of 6.2 and 0.8 kOe for the out-of-plane and in-plane directions, respectively. The FePt nanoparticle monolayer sputter-deposited on polycrystalline TiN seed layer is a promising candidate for perpendicular magnetic recording media.

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    4
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  • Growth mode during initial stage of chemical vapor deposition

    Y Kajikawa, S Noda

    APPLIED SURFACE SCIENCE   245 ( 1-4 ) 281 - 289  2005.05  [Refereed]

     View Summary

    The initial stage during vapor deposition has been extensively studied in physical vapor deposition (PVD) processes, and nucleation theories have been successfully used to model island nucleation processes during PVD. Compared with the extensive research in PVD, there has been less work on understanding the initial stage in chemical vapor deposition (CVD) processes, despite the technological and commercial importance of CVD-based manufacturing systems. In this work we briefly review the nucleation theories developed for PVD processes and consider the validity of them for modeling the initial stage of CVD processes. One characteristic of CVD processes is the existence of an incubation time. Recent research indicates that the incubation time can be caused by the different reactivity of precursors nucleating on substrates and islands. We proposed process indices to evaluate the relative importance of sticking probabilities and desorption of adsorbates on the incubation time. The differing precursor reactivity between islands and substrates may also affect the island growth mode. This situation in CVD processes differs from that in PVD processes, for which current nucleation theories were developed, and therefore prevents the direct application of PVD nucleation theories to CVD processes. Therefore, to model CVD processes, a nucleation model is needed that is sensitive to the different reactivity of precursors to islands and substrates. &COPY; 2004 Elsevier B.V. All rights reserved.

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    48
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  • Combinatorial method to prepare metal nanoparticles that catalyze the growth of single-walled carbon nanotubes

    S Noda, Y Tsuji, Y Murakami, S Maruyama

    APPLIED PHYSICS LETTERS   86 ( 17 ) 173106  2005.04  [Refereed]

     View Summary

    Enhanced surface diffusion at the growth temperature of single-walled carbon nanotubes (SWNTs) can cause coarsening of metal catalysts. By balancing the nominal thickness and surface diffusion length of metals, metal nanoparticles of desirable size are expected to form spontaneously under the SWNTs growth conditions. Our combinatorial method, using a library of nominally 0.001 to 1 nm thick sputter-deposited cobalt patterns, identified in a single experimental run that cobalt nanoparticles from submonolayers can catalyze the growth of high-quality SWNTs. (c) 2005 American Institute of Physics.

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    49
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  • Structuring knowledge on nanomaterials processing

    H Komiyama, Y Yamaguchi, S Noda

    CHEMICAL ENGINEERING SCIENCE   59 ( 22-23 ) 5085 - 5090  2004.11  [Refereed]

     View Summary

    Materials science is divided into disciplines based on the properties of bulk materials. However, common rules that govern phenomena at nanoscales are eliminating those boundaries between disciplines. in order to support more effective education, research, development, and manufacturing in materials science, a Japanese national project for structuring knowledge of materials nanotechnology is underway. Examples of the effect of structuring knowledge on the relationships between processes and material structures are shown for vapor-deposition processes and nanoparticle coating and drying processes. A knowledge platform, into which this generalized nanotechnology knowledge is to be integrated, is outlined in this paper. The key purpose of structuring knowledge is to stimulate idea generation based on a fundamental and general understanding of underlying mechanisms. (C) 2004 Published by Elsevier Ltd.

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    5
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  • Stranski-Krastanov growth of tungsten during chemical vapor deposition revealed by micro-auger electron spectroscopy

    S Noda, T Tsumura, J Fukuhara, T Yoda, H Komiyama, Y Shimogaki

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS   43 ( 10 ) 6974 - 6977  2004.10  [Refereed]

     View Summary

    Chemical vapor deposition (CVD) of tungsten is an important process to make interconnections in advanced integrated-circuit devices. As device dimensions continue to decrease, incomplete nucleation inside the trenches and via holes is becoming a crucial issue. In this work, micro-Auger electron spectroscopy with in-plane spatial resolution was applied for the first time to study the nucleation and growth process of W islands. Results showed that W grew slowly and uniformly on TiN surfaces up to about one-monolayer coverage, and then W islands nucleated and started to grow rapidly. This transition from layer to island shows that W grew by Stranski-Krastanov mode during CVD on TiN from WF6 and SiR4. Drastic difference might exist in chemical reactivity between the-initial W layer on TiN surfaces and the W islands, causing the change in W growth rate.

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    6
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  • A simple index to restrain abnormal protrusions in films fabricated using CVD under diffusion-limited conditions

    Y Kajikawa, S Noda, H Komiyama

    CHEMICAL VAPOR DEPOSITION   10 ( 4 ) 221 - 228  2004.09  [Refereed]

     View Summary

    Cauliflower-like protrusions formed in CVD processes under diffusion-limited conditions have been studied both experimentally and theoretically. Both approaches indicate that the difference in diffusion fluxes to the film and to the protrusions controls the growth of such protrusions. However, direct comparisons of these two approaches have never been done, probably due to the complexity of the theoretical models. To simplify model protrusion growth, we developed a one-dimensional (1D) analytical model by hypothesizing the diffusion of growth species in the boundary layer above a growing film. Based on this model, we propose a non-dimensional quantity, k(s)f/D, as an index of protrusion growth (D is the diffusion coefficient of the growth species, k(s) is the surface reaction-rate coefficient, and f is film thickness). This index represents more directly the protrusion growth than does the previously proposed index, the Damkohler number, Da = k(s)delta/D, where delta is boundary layer thickness. To obtain smooth, protrusion-free films, D/k(s) should be kept larger than the desired film thickness. By controlling the process conditions to satisfy this index, we successfully fabricated protrusion-free films with SiC deposition from dichlorodimethylsilane (DDS).

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  • Selective silicidation of Co using silane or disilane for anti-oxidation barrier layer in Cu metallization

    S Noda, R Hirai, H Komiyama, Y Shimogaki

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS   43 ( 9A ) 6001 - 6007  2004.09  [Refereed]

     View Summary

    Aiming to realize a conductive passivation layer for copper interconnection, the solid-gas reactions of cobalt films with silane and with disilane to form cobalt silicides are experimentally investigated. X-ray photoelectron spectroscopy revealed that cobalt silicides layers of up to 6 nm thickness can be selectively formed in the reaction at 473-673 K within 5 min without detectable silicon deposition on silicon dioxide, a common inter-metal dielectric layer. Rapid thermal oxidation experiments revealed that the silicided cobalt layers had better anti-oxidation performance than untreated cobalt layers, and the effect of silicidation was to suppress copper out-diffusion through the cobalt layers. Because cobalt-based alloys can be selectively electroless-plated on copper, selective silicidation of cobalt layers will be easily incorporated into device processing.

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    5
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  • Wettability and crystalline orientation of Cu nanoislands on SiO2 with a Cr underlayer

    M Hu, S Noda, T Okubo, H Komiyama

    APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING   79 ( 3 ) 625 - 628  2004.08  [Refereed]

     View Summary

    Cu thin films were grown by sputter deposition on SiO2 substrates with a Cr underlayer that is known to improve the adhesion between Cu and SiO2. The initial stage of Cu growth was investigated using transmission electron microscopy. Results showed that non-wetting spherical Cu nanoislands were formed with a random crystalline orientation on Cr/SiO2, and evolved into a randomly oriented polycrystalline thin film. These results were then compared with our previous results on the initial growth of Cu on SiO2 with and without a Ti underlayer. A quantitative model was proposed to explain the difference in dependence of the wettability of microscopic nanoislands and that of the adhesion of macroscopic thin films on interfacial interactions and surface energies.

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    9
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  • Use of process indices for simplification of the description of vapor deposition systems

    Y Kajikawa, S Noda, H Komiyama

    MATERIALS SCIENCE AND ENGINEERING B-SOLID STATE MATERIALS FOR ADVANCED TECHNOLOGY   111 ( 2-3 ) 156 - 163  2004.08  [Refereed]

     View Summary

    Vapor deposition is a complex process, including gas-phase, surface, and solid-phase phenomena. Because of the complexity of chemical and physical processes occurring in vapor deposition processes, it is difficult to form a comprehensive, fundamental understanding of vapor deposition and to control such systems for obtaining desirable structures and performance. To overcome this difficulty, we present a method for simplifying the complex description of such systems. One simplification method is to separate complex systems into multiple elements, and determine which of these are important elements. We call this method abridgement. The abridgement method retains only the dominant processes in a description of the system, and discards the others. Abridgement can be achieved by using process indices to evaluate the relative importance of the elementary processes. We describe the formulation and use of these process indices through examples of the growth of continuous films, initial deposition processes, and the formation of the preferred orientation of polycrystalline films. In this paper, we propose a method for representing complex vapor deposition processes as a set of simpler processes. (C) 2004 Elsevier B.V. All rights reserved.

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    8
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  • Incubation time during the CVD of Si onto SiO2 from silane

    Y Kajikawa, T Tsuchiya, S Noda, H Komiyama

    CHEMICAL VAPOR DEPOSITION   10 ( 3 ) 128 - +  2004.06  [Refereed]

     View Summary

    Communication: Mechanisms controlling the deposition incubation time of Si on SiO2 are studied. Two major mechanisms are considered to affect the incubation time: desorption of adsorbate that is not captured by existing islands, and differing sticking probabilities between islands and substrate. Results indicate that desorption of adsorbate seems to have less contribution and the sticking probability mechanism controls island growth (Figure), and therefore is the main cause for the incubation time in silane CVD processes.

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    25
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  • Nucleation of W during chemical vapor deposition from WF6 and SiH4

    Y Kajikawa, T Tsumura, S Noda, H Komiyama, Y Shimogaki

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS BRIEF COMMUNICATIONS & REVIEW PAPERS   43 ( 6B ) 3945 - 3950  2004.06  [Refereed]

     View Summary

    A gas mixture of tungsten hexafluoride (WF6) and silane (SiH4) is generally used to form the initial layer of tungsten (W) on titanium nitride (TiN). However, the nucleation mechanism is still not clear, thus making it difficult to optimize such processes for complete filling of via holes. Therefore, in this study, we examined the nucleation process by laser-reflection measurements, scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). These measurements indicate that W nucleation has two stages: monolayer formation followed by nucleation of three-dimensional (3D) islands. The monolayer formation can be expressed as Langmuir-type adsorption, and proceeds with the reduction of WF6 by Ti on TiN substrates. After monolayer formation, nucleation of 3D islands occurs and islands rapidly grow. These processes were quantitatively modeled using a simple rate equation. The results of our model agree well with our measurements of the deposited amount and coverage of islands.

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    20
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  • Preferred orientation and film structure of TaN films deposited by reactive magnetron sputtering

    S Noda, K Tepsanongsuk, Y Tsuji, Y Kajikawa, Y Ogawa, H Komiyama

    JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A   22 ( 2 ) 332 - 338  2004.03  [Refereed]

     View Summary

    The structural evolution of tantalum nitride (TaN) films deposited by reactive rf magnetron sputtering were investigated in detail by using transmission electron microscopy (TEM) and x-ray diffractometry (XRD) for a wide range of thickness from 2 nm to 2 mum under various N-2 /Ar flow ratios from 0 to 20 vol % on both amorphous SiO2 (a-SiO2) and randomly oriented polycrystalline fee TaN (poly-fcc-TaN) substrates. Although the films had various crystalline structures [including tetragonal Ta, bee Ta(N), and fee TaN] of different preferred orientation (PO) and had amorphous phases depending on deposition conditions, the formation mechanism of these structures was systematically explained by mapping them on 2D graphs of film thickness vs N-2 /Ar flow ratio. The texture map of films deposited on a-SiO2 substrates reflected both nucleation and growth stages, whereas that of films deposited on poly-fcc-TaN substrates reflected mainly the growth stage. Comparison of these two maps allowed the nucleation and growth processes to be separately discussed. For films deposited. at 4 vol % N-2 /Ar ratio on a-SiO2 substrates, an amorphous phase initially appeared when the film thickness was 1.8-3.5 nm. When the film thickness was about 7 nm, nucleation occurred to form fee TaN without any PO. When the thickness was about 100 nm, (111) PO appeared. Finally, when the thickness exceeded 200 nm, (200) PO dominated the film. Cross-sectional TEM micrographs revealed that evolutionary selection growth occurred when the film was 200-nm-thick to cause the PO change. (111) PO was preferred at relatively low (2-3 vol %) and high (greater than or equal to10 vol %) N-2/Ar ratios, whereas (200) was preferred at medium N-2/Ar ratio (4-7 vol %). (C) 2004 American Vacuum Society.

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    18
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  • Combinatorial masked deposition: simple method to control deposition flux and its spatial distribution

    S Noda, Y Kajikawa, H Komiyama

    APPLIED SURFACE SCIENCE   225 ( 1-4 ) 372 - 379  2004.03  [Refereed]

     View Summary

    Deposition flux is an important factor that determines the structures of, vapor-deposited materials. However, controlling this flux over a wide range is difficult using only a single apparatus. In-this work, we developed a simple method, called combinatorial masked deposition (CMD), that enables a series of deposition fluxes and their respective distribution to be realized on a single sample by just setting a mask with holes of different sizes above a substrate. The degree of reduction in deposition flux can be controlled by the hole size and distance between the given point and the hole. The characteristics and applicability of CMD were evaluated by two experiments. In the first experiment, Cu nanoparticles were formed by sputter-deposition on a-SiO2 at different Cu deposition fluxes. The nanoparticles had a higher number density and smaller size when deposited at 0.80 nm/s for 2.5 s than when deposited at 0.014 nm/s for 140 s. In the second experiment, metal-induced crystallization of amorphous Si (a-Si) was done with spatially distributed Ni additives. The CMD method can realize a series of Ni flux distributions and was successfully used to form 100 different profiles of Ni concentration on a single sample, thus enabling efficient screening of concentration profiles to enhance grain size. (C) 2003 Elsevier B.V. All rights reserved.

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    20
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  • Initial Nucleation and Growth in Fabrication of Metal Thin Films by Chemical Vapor Deposition

    Shimogaki Yukihiro, Sugiyama Masakazu, Noda Suguru, Komiyama Hiroshi

    Asian Pacific Confederation of Chemical Engineering congress program and abstracts   2004   944 - 944  2004

     View Summary

    The ever growing ULSI device integration now requires ultra thin films as low as several nano-meter level. The so-called layer by layer growth is the ideal for making thin films for these requirements but island growth often occurred in metal CVD to deposit Al, W and Cu thin films on barrier layers, mostly composed of TiN or Ta/TaN films. We have made in-situ monitoring of initial nucleation behavior using laser light reflectivity measurement. This technique enables us to monitor the incubation period during which no nuclei formation is observed. The surface adsorbates during the incubation period was monitored by XPS and we found that the reactivity of initial surface and the film precursor is determining the incubation period.

    DOI CiNii

  • Reaction of Si with HCl to form chlorosilanes - Time dependent nature and reaction model

    S Noda, K Tanabe, T Yahiro, T Osawa, H Komiyama

    JOURNAL OF THE ELECTROCHEMICAL SOCIETY   151 ( 6 ) C399 - C404  2004  [Refereed]

     View Summary

    We propose a chemical vapor deposition (CVD) process with closed gas recycling for making low-cost, crystalline silicon thin films for solar cells, which connects chlorosilane synthesis from Si and HCl with Si thin-film growth by CVD from chlorosilanes. In this work we studied the formation of chlorosilanes by the reaction of Si with HCl at temperatures ranging from 623 to 723 K. The reaction rate is time dependent, and many pores are formed on the surface of particles after reaction. These pores are active sites for chemical reactions, and the reaction rates increase with increasing pore area. The rate can be correlated with the conversion ratio of Si, and the temporal evolution of the reaction rate can be explained by a reaction model called the shrinking-core model with growing pores. By using this model, we estimated the reaction rates per unit area of activated surfaces and converted them into a rate equation that can be used for the reactor design. The incubation time of the reaction can be shortened by pretreating the Si particles in a fluidized bed, which probably creates defects in the native oxide layers on the particles, which in turn become reactive sites. (C) 2004 The Electrochemical Society.

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    13
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  • Comprehensive perspective on the mechanism of preferred orientation in reactive-sputter-deposited nitrides

    Y Kajikawa, S Noda, H Komiyama

    JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A   21 ( 6 ) 1943 - 1954  2003.11  [Refereed]

     View Summary

    Texture control of sputter-deposited nitride films has provoked a great deal of interest due to its technological importance. Despite extensive research, however, the reported results are scattered and discussions about the origin of preferred orientation (PO) are sometimes conflicting, and therefore controversial. The aim of this study is to acquire a clear perspective in order to discuss the origin of PO of sputter-deposited nitrides. Among nitrides, we focus on titanium nitride (TiN), aluminum nitride (AlN), and tantalum nitride (TaN), which are three commonly used nitrides. First, we collected reported experimental results about the relation between operating conditions and PO, because PO is considered to be determined by film formation processes, such as surface diffusion or grain growth, which is affected by operating conditions. We also collected reported results about such PO-determining processes. Then, we categorized the PO-determining processes into an initial stage and a growth stage of film deposition, and further categorized each stage into a vapor-solid interface and a solid-solid interface. Then, we related each stage and interface to film morphology and to PO-determining processes. Finally, based on existing results, previous models, and proposed schema, we discuss the origin of PO. Based on previous experimental results on film morphology, PO of nitride films occurred in the growth stage at the vapor-solid interface, where the sticking process of the precursor and the surface diffusion process determine PO, rather than in the initial stage and in the growth stage at the solid-solid interface. TiN (002) PO, however, seems to be caused in the initial stage at the solid-solid interface. (C) 2003 American Vacuum Society.

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  • Effects of substrate heating and biasing on nanostructural evolution of nonepitaxially grown TiN nanofilms

    TQ Li, S Noda, F Okada, H Komiyama

    JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B   21 ( 6 ) 2512 - 2516  2003.11  [Refereed]

     View Summary

    The effects of substrate heating and substrate biasing on. the initial stage of nonepitaxial heterogeneous growth of TiN on Si(111) was studied by using high-resolution transmission electron microscopy. Although TiN films deposited at room temperature (RT) undergo a transition from continuous amorphous films to polycrystalline films with three-dimensional grains when the film thickness is increased from similar to1 to 2 nm, crystallization occurred at a substrate temperature, T-s = 570 K, even for film thicknesses less than 1 nm. Compared with growth at T-s = RT, at T-s = 570 K, the initial lateral grain size was only slightly larger, and the grains tended to be spherical and discontinuous at higher film thickness. At a substrate bias voltage, V-b = -70 V-b the grains were laterally larger and planar. At a film thickness of 50 nm, the films deposited at V-b = -70 V showed the thermodynamically favored (200) preferred orientation, whereas the films deposited at T-s = 570 K showed (111) preferred orientation with a weak (200) peak. (C) 2003 American Vacuum Society.

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    15
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  • Structural and morphological control of nanosized Cu islands on SiO2 using a Ti underlayer

    MH Hu, S Noda, T Okubo, Y Yamaguchi, H Komiyama

    JOURNAL OF APPLIED PHYSICS   94 ( 5 ) 3492 - 3497  2003.09  [Refereed]

     View Summary

    The structure and morphology of nanosized Cu islands grown by sputter deposition on clean SiO2 substrates and Ti-underlayered SiO2 substrates are investigated using transmission electron microscopy. On SiO2, spherical Cu islands with a random crystalline orientation are formed, whereas on Ti/SiO2, semispherical islands with a preferred &lt;111&gt; crystalline orientation are formed. Moreover, the Cu islands on Ti/SiO2 have smaller sizes, shorter interisland distances, and a higher number density than those on SiO2. These structural and morphological changes at the nanoscale are discussed from the viewpoint of interfacial interactions. Our study suggests that by using an appropriate metal underlayer, it is possible to fabricate nanosized islands with the desired wettability, crystalline orientation, as well as morphology of island ensembles. (C) 2003 American Institute of Physics.

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  • Initial growth stage of nanoscaled TiN films: Formation of continuous amorphous layers and thickness-dependent crystal nucleation

    TQ Li, S Noda, H Komiyama, T Yamamoto, Y Ikuhara

    JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A   21 ( 5 ) 1717 - 1723  2003.09  [Refereed]

     View Summary

    The initial growth stage of titanium nitride (TiN) deposited by reactive magnetron dc sputtering onto (111)-oriented Si substrates was investigated by using high-resolution transmission electron microscopy (HRTEM). During the initial growth stage, a continuous amorphous layer was observed when the deposited film was less than I nm thick. Crystal nucleation occurred from the amorphous layer when the film grew to about 2 nm thick. No pref erred orientation was found for the initial crystal nuclei. The growth of the crystal grains depended on the N-2 partial pressure, P-N2. Increasing P-N2 from 0.047 to 0.47 Pa enhanced lateral grain growth and coalescence between grains. For P-N2 = 0.47 Pa, planar grains with a large lateral dimension were found formed by grain growth and coalescence; inducing a (200) film orientation. For films formed at P-N2 = 0.47 Pa, an amorphous interlayer 1.5-1.8 nm thick formed between the TiN layer and Si substrate, and was indicated to be primarily SiNx by x-ray photoelectron spectroscopy and HRTEM. This interlayer was less than 0.5 nm thick in films formed at P-N2 = 0.047 Pa. (C) 2003 American Vacuum Society.

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    36
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  • Amorphous-to-crystalline transition during the early stages of thin film growth of Cr on SiO2

    MH Hu, S Noda, H Komiyama

    JOURNAL OF APPLIED PHYSICS   93 ( 11 ) 9336 - 9344  2003.06  [Refereed]

     View Summary

    The growth of sputter-deposited Cr thin films on amorphous SiO2 during the early stages was studied using transmission electron microscopy. Amorphous three-dimensional islands were first formed, and then they grew with continuously increasing density and slowly increasing size as the deposition proceeded. When these islands began to coalesce at a nominal film thickness of 2.3-3.0 nm, they abruptly crystallized into randomly oriented crystalline nuclei. The depth profile analysis by x-ray photoelectron spectroscopy indicates the existence of interfacial Cr-O interactions. After excluding-the possibilities of kinetic limitation and interfacial mixing, a thermodynamic model was employed to explain the size-dependent amorphous-to-crystalline transition. Our results suggest that the interfacial-interaction-induced strain relaxation at island/substrate interfaces might result in the thermodynamic stabilization of substrate-supported amorphous islands below a critical size. (C) 2003 American Institute of Physics.

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    23
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  • Mechanisms controlling preferred orientation of chemical vapour deposited polycrystalline films

    Y Kajikawa, S Noda, H Komiyama

    POLYCRYSTALLINE SEMICONDUCTORS VII, PROCEEDINGS   93   411 - 416  2003  [Refereed]

     View Summary

    In the absence of epitaxy between a film and a substrate, the preferred orientation of polycrystalline films can often be explained by the "evolutionary selection rule", which states that grains with the fastest growing direction normal to the substrate envelope the other grains and determine the final orientation of the film. However, the mechanism determining the fastest growing plane and the factors affecting the growth rates of each plane are still not well understood. We examined existing experimental results in the previous literatures and found a correlation between process conditions and preferred orientation for poly-Si and poly-SiC thin films. We present a model based on Langmuir-type adsorption for predicting preferred orientation, which agrees well with experimental results in the previous literatures for Si and SiC.

  • A new insight into the growth mode of metals on TiO2(110)

    M Hu, S Noda, H Komiyama

    SURFACE SCIENCE   513 ( 3 ) 530 - 538  2002.08  [Refereed]

     View Summary

    The growth of metals on TiO2(1 10) at one monolayer coverage is classified into three-dimensional island, twodimensional layer, and transition growth zones via two thermodynamic parameters, the heat of formation of metal oxides, -Delta(f)H(oxide of M)(0), and the heat of sublimation of metals, -Delta(f)H(metal, per mol of metal)(0) (both expressed per mol of metal), which are easily obtainable. These two parameters represent the strength of metal/TiO2(110) interfacial interactions and the strength of metal/metal lateral interactions, respectively. Such classification is based on the thermodynamic criteria that the growth mode of metals on TiO2(110) is determined by metal/TiO2 interfacial free energy and metal surface free energy. Compared with the conventional approach that only uses the heat of formation of metal oxides, -Delta(f)H(oxide of O)(0) (expressed per mol of oxygen), our model provides a clearer and more comprehensive vision of the growth mode of metals on TiO2(110) and the factors affecting the growth mode. The approach described in this study can also be applied to other metal/reducible oxide systems. (C) 2002 Elsevier Science B.V. All rights reserved.

    DOI

    Scopus

    54
    Citation
    (Scopus)
  • Initial growth and texture formation during reactive magnetron sputtering of TiN on Si(111)

    TQ Li, S Noda, Y Tsuji, T Ohsawa, H Komiyama

    JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A   20 ( 3 ) 583 - 588  2002.05  [Refereed]

     View Summary

    The initial growth and texture formation mechanism of titanium nitride (TiN) films were investigated by depositing TiN films on (111) silicon substrates by using reactive magnetron sputtering of a Ti metallic target under a N-2/Ar atmosphere, and then analyzing the films in detail by using transmission electron microscopy (TEM) and x-ray diffraction (XRD). Two power sources for the sputtering, dc and rf, were compared. At the initial growth stage, a continuous amorphous film containing randomly oriented nuclei was observed when the film thickness was about 3 nm. The nuclei grew and formed a polycrystalline layer when the film thickness was about 6 nm. As the film grew further, its orientation changed depending on the deposition conditions. For dc sputtering, the appearance of (111) or (200)-preferred orientations depended on the N-2 partial pressure, and the intensity of the preferred orientation increased with increasing film thickness. For rf sputtering, however, when the film thickness was small (for instance, about 20 nm), the film showed (200) orientation, independent of the N2 partial pressure, and further growth caused the film to orient to the (111) orientation when the N-2 partial pressure was low (about 0.015 Pa). The results indicated that preferred orientation of TiN films is controlled by a competition between kinetic and thermodynamic effects. (C) 2002 American Vacuum Society.

    DOI

    Scopus

    80
    Citation
    (Scopus)
  • Effect of interfacial interactions on the initial growth of Cu on clean SiO2 and 3-mercaptopropyltrimethoxysilane-modified SiO2 substrates

    M Hu, S Noda, Y Tsuji, T Okubo, Y Yamaguchi, H Komiyama

    JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A-VACUUM SURFACES AND FILMS   20 ( 3 ) 589 - 596  2002.05  [Refereed]

     View Summary

    The effect of interfacial interactions on the initial growth of Cu on clean SiO2 and 3-mercaptopropyltrimethoxysilane (MPTMS)-modified SiO2 substrates by sputter deposition was studied using transmission electron microscopy, energy dispersive x-ray spectroscopy, and x-ray photoelectron spectroscopy. Plasma damage during sputter deposition makes surfaces of MPTMS-modified SiO2 substrates consist of small MPTMS islands several tens of nanometers in diameter and bare SiO2 areas. These MPTMS islands are composed of disordered multilayer MPTMS aggregates. The initial growth behavior of Cu on MPTMS-modified SiO2 substrates differs from that on clean SiO2 substrates, although Cu grows in three-dimensional-island mode on both of them. After a 2.5-monolayer Cu deposition on clean SiO2 substrates, spherical Cu particles were formed at a low number density of 1.3 x 10(16) /m(2) and at a long interparticle distance of 5 nm. In contrast, after the same amount of deposition on MPTMS-modified SiO2 substrates, Cu particles preferentially grow on MPTMS islands at a high number density of 3.9 x 10(16) /m(2) and at a short interparticle distance of 3 run, but do not grow on bare SiO2 areas. The increased number density and the decreased interparticle distance indicate that Cu has a lower mobility on MPTMS islands on MPTMS-modified SiO2 substrates than on clean SiO2 substrates. This difference in Cu mobility is attributed to the enhanced interfacial interactions between Cu and S on MPTMS islands on MPTMS-modified SiO2 substrates via the formation of Cu-S bonds, compared with the relatively weak interfacial interactions between Cu and Si or O on clean SiO2 substrates. (C) 2002 American Vacuum Society.

    DOI

    Scopus

    46
    Citation
    (Scopus)
  • Cone structure formation by preferred growth of random nuclei in chemical vapor deposited epitaxial silicon films

    S Noda, Y Kajikawa, H Komiyama

    CHEMICAL VAPOR DEPOSITION   8 ( 3 ) 87 - +  2002.05  [Refereed]

     View Summary

    Communication: Systematic creation of abnormal structures in silicon epitaxial growth is studied. The abnormalities are induced by randomly dispersing 2-4 mum sized diamond particles onto silicon substrates When the epitaxial plane is not the fastest growing one, elongated crystallites form a radial pattern from the particles enveloped in the epitaxial film, resulting in cone structures much larger than the seed particles

    DOI

    Scopus

    6
    Citation
    (Scopus)
  • Preferred orientation of chemical vapor deposited polycrystalline silicon carbide films

    Y Kajikawa, S Noda, H Komiyama

    CHEMICAL VAPOR DEPOSITION   8 ( 3 ) 99 - 104  2002.05  [Refereed]

     View Summary

    We investigated the mechanism that determines the preferred orientation of polycrystalline silicon carbide (SiC) films prepared by CVD from a mixture of dichlorodimethylsilane (DDS) and He. X-ray diffraction (XRD) measurements indicated that the major growth direction is either the (220) or the (111) plane. We developed a numerical model for predicting the preferred orientation, assuming Langmuir-type adsorption and reaction of the growth species. This model suggests that the (111) plane appears under reaction-limited deposition. while the (220) plane appears under adsorption-limited deposition. Our experimental and numerical results show good qualitative agreement with experimental results for films prepared from methyltrichlorosilane (MTS) and H-2.

    DOI

    Scopus

    54
    Citation
    (Scopus)
  • Growth of trumpet-like protrusions during the CVD of silicon carbide films

    Y Kajikawa, H Ono, S Noda, H Komiyama

    CHEMICAL VAPOR DEPOSITION   8 ( 2 ) 52 - +  2002.03  [Refereed]

     View Summary

    Communication: The deposition of trumpet-like protrusions during CVD of SiC is reported. The protrusions are deposited at the flow stagnation point of an impinging flow reactor. SEM analysis of the structures (Figure) indicates that they consist of aggregates of 1 mum sized particles surrounded by a smooth and dense film, which suggests a possible growth mechanism that produces preferential thermophoretic deposition on the protrusions rather than on the surface of the films.

    DOI

    Scopus

    3
    Citation
    (Scopus)
  • Internal microstructure and formation mechanism of surface protrusions in Pb-Ti-Nb-O thin films prepared by MOCVD

    XD Liu, H Funakubo, S Noda, H Komiyama

    CHEMICAL VAPOR DEPOSITION   7 ( 6 ) 253 - 259  2001.11  [Refereed]

     View Summary

    Pb-Ti-Nb-O ferroelectric thin films with various Nb additions are grown on a Pt/Ti/SiO2/Si substrate at 400 degreesC by metal-organic (MO) CVD. A high density of dome-like surface protrusions is observed by scanning electron microscopy (SEM) in all the as-prepared films. Both the shape and the size of the surface defects are found to be Nb-content-dependent. The internal microstructure of the protrusions is further characterized by cross-section transmission electron microscopy (XTEM). The origins of these surface defects are discussed, based on the substrate hillock as well as the crystallization behavior of the film forming precursors during MOCVD. The development of the observed surface defects is modeled using a two-dimensional vector analysis.

    DOI

    Scopus

    7
    Citation
    (Scopus)
  • Structure and morphology of self-assembled 3-mercaptopropyltrimethoxysilane layers on silicon oxide

    MH Hu, S Noda, T Okubo, Y Yamaguchi, H Komiyama

    APPLIED SURFACE SCIENCE   181 ( 3-4 ) 307 - 316  2001.09  [Refereed]

     View Summary

    Self-assembled 3-mereaptopropyltrimethoxysilane (MPTMS, (CH3O)(3)SiCH2CH2CH2SH) layers on hydroxyl-terminated silicon oxide (SiO2) were prepared at MPTMS concentrations ranging from 5 x 10(-3) to 4 x 10(-2) M. The surface structure and morphology of MPTMS layers were characterized by X-ray photoelectron spectroscopy (XPS), contact angle measurements, scanning electron microscopy (SEM), and atomic force microscopy (AFM). We found that the MPTMS layers on SiO2 consisted of dispersed domains 20-200 run in diameter, instead of continuous, flat monolayers. With increasing MPTMS concentration, the domain shape changed from flat to steep. Flat domains were composed of well-ordered monolayers with thiol headgroups uniformly distributed on the uppermost surface, whereas steep domains were composed of disordered polymers with randomly distributed thiol headgroups on the uppermost surface. These results indicate that MPTMS molecules show good self-assembly at an MPTMS concentration of 5 x 10(-3) M, but not above this concentration. The effect of MPTMS concentration on the structure and morphology of MPTMS layers might be due to the competition between self-polymerization and surface dehydration reactions, which depends on the trace quantity of water in the solvent and on the SiO2 surface. Our research further indicates that MPTMS and water concentrations are the controlling parameters for preparing well-ordered, self-assembled MPTMS monolayers on SiO2. (C) 2001 Elsevier Science B.V All rights reserved.

    DOI

    Scopus

    170
    Citation
    (Scopus)
  • NO reduction under the excess O-2 condition by porous VYCOR catalyst

    M Yamamoto, S Ona, S Noda, M Sadakata

    JOURNAL OF CHEMICAL ENGINEERING OF JAPAN   34 ( 6 ) 834 - 839  2001.06  [Refereed]

     View Summary

    Exhaust gas from a diesel engine is one of the main causes of air pollution. It is difficult to reduce NO under the excess O-2 concentration so that effective method of NO reduction has not been developed. In this study, nickel on the porous glass (VYCOR(R) glass) was examined as a catalyst for NO reduction. This catalyst was effective for NO reduction where 35% of NO was converted to N-2 under excess O-2 concentration (3%) in the tubular fixed-bed reactor. Adsorption rates of NO and O-2 gases were measured in order to examine the mechanism of selective reduction of NO by porous VYCOR catalyst. It was proved that NO adsorption rate was much higher than O-2 adsorption rate, so that difference of adsorption rate was one of the main causes of NO reduction. As a short lifetime of the-catalyst was the serious disadvantage of the tubular fixed-bed reactor, another type of catalytic reactor was proposed and tested. It is a membrane reactor consisting of a porous VYCOR catalyst tube and a quartz tube. NO reduction under excess O-2 concentration was also achieved in the membrane reactor. Maximum conversion from NO to N-2 was 45%. The possibility of longer lifetime catalyst could be found.

  • Influence of deposition temperature on the microstructure of Pb-Ti-Nb-O thin films by metallorganic chemical vapor deposition

    XD Liu, H Funakubo, S Noda, H Komiyama

    JOURNAL OF THE ELECTROCHEMICAL SOCIETY   148 ( 3 ) C227 - C230  2001.03  [Refereed]

     View Summary

    In the current study, we grew Pb-Ti-Nb-O (PTN) thin films on Pt/Ti/SiO2/Si substrate by metallorganic chemical vapor deposition (MOCVD) at temperatures ranging from 400 to 620 degreesC. The thin films obtained were examined by X-ray diffraction and cross-sectional transmission electron microscopy. It was revealed that both the PTN film and its interface with the underlying Pt layer were quite sensitive to variations in the deposition temperature. The considerable change in surface morphology of PTN thin films with an enhanced deposition temperature is discussed in relation to the surface hillocks formed on the Pt layer by aggregation of the out-diffused Pt atoms during MOCVD. (C) 2001 The Electrochemical Society.

    DOI

    Scopus

    9
    Citation
    (Scopus)
  • Gas-phase hydroxyl radical emission in the thermal decomposition of lithium hydroxide

    S Noda, M Nishioka, M Sadakata

    JOURNAL OF PHYSICAL CHEMISTRY B   103 ( 11 ) 1954 - 1959  1999.03  [Refereed]

     View Summary

    The gas-phase hydroxyl(OH) radical emission was observed in the thermal decomposition of lithium hydroxide: (LIOH). This phenomenon was investigated in a vacuum flow tube reactor at around 2 Torr by the temperature programmed reaction (TPR) experiments at 500-1300 K. The production of OH and other gaseous products was quantitatively investigated by the laser induced fluorescence method and quadrupole mass spectrometry, respectively. The TPR spectra of OH had a peak at 1100-1200 K, which largely exceeded the gas-phase thermodynamic equilibrium. The origin of OH was supposed to be either the surface OH groups on Li2O or the residual LiOH in the LiOH/Li2O solid solution. OH production exceeding the thermodynamic equilibrium was explained by means of the partial equilibrium in the reaction: LiOH + 1/4O(2) &lt;-&gt; 1/2Li(2)O + OH. This phenomenon can be a new route for the OH production from H2O and O-2 in cyclic reactions of lithium compounds.

    DOI

  • Gas-phase hydroxyl radical generation by the surface reactions over basic metal oxides

    S Noda, M Nishioka, A Harano, M Sadakata

    JOURNAL OF PHYSICAL CHEMISTRY B   102 ( 17 ) 3185 - 3191  1998.04  [Refereed]

     View Summary

    Hydroxyl radical desorption in the heterogeneous catalytic reactions of water or hydrogen with oxygen was examined by laser-induced fluorescence spectroscopy. The catalytic activities of Pt, Al2O3, and basic metal oxides (MgO, CaO, SrO, BaO) supported on Al2O3 were studied in the pressure range 0.1-10 Torr and the temperature range 1100-1300 K. In the case of OH generation from water, the catalytic activities of Pt and all oxides except Al2O3 were very high and the OH concentration reached the equilibrium value within a residence time of 4 ms. In the case of hydrogen oxidation, differences in the catalytic behavior were clearly observed. The surface reaction mechanisms and the effects of Al2O3 and MgO on gas-phase ignition are discussed.

    DOI

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Research Projects

  • Development of safe and high-performance secondary batteries based on nanotubes and assessment of their impacts on reduction of greenhouse gas emission

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research

    Project Year :

    2021.04
    -
    2024.03
     

  • Development of practical production methods of boron nitride nanotubes

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research

    Project Year :

    2021.07
    -
    2023.03
     

  • Mechanistic study on metal chalcogenides catalyzed water splitting for efficient hydrogen production

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for JSPS Fellows

    Project Year :

    2019.04
    -
    2021.03
     

  • Creating Soft-Batteries by Simple and Rapid Processes and Innovating Capacity by Reversible Structure Change

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (S)

    Project Year :

    2016.05
    -
    2021.03
     

    Noda Suguru

     View Summary

    A novel battery architecture and its manufacturing process were proposed and developed to meet society's high demand for high energy-density rechargeable batteries. Since high-capacity active materials such as silicon and sulfur undergo large volume changes as a large amount of lithium ions move in and out of them, reversible operation was realized by holding them in electrically conductive and mechanically flexible sponge films of carbon nanotubes. The “soft battery” that maintains a constant volume and works stably while having shrinking/expanding cathode/anode during charge (and vice versa during discharge) was developed, and a high energy density was achieved.

  • Creation and simple fabrication of crystalline silicon film-carbon nanotube flexible solar cells

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Challenging Exploratory Research

    Project Year :

    2015.04
    -
    2017.03
     

    Noda Suguru, YAMASAKI Yuhei, MURAMOTO Rie, FUJITA Makoto, ISHIJIMA Naoya, HASEGAWA Kei, SUGIME Hisashi, OSAWA Toshio

     View Summary

    We conducted this research to realize light-weight, stable, low-cost flexible solar cells using abundant chemical elements of carbon and silicon via simple, rapid, high-yield processes. We developed a rapid vapor deposition process to make Si films to use high-purity Si several ten-times more efficiently than the present bulk crystalline Si solar cells. Si is rapidly deposited at 10 μm in 1 min by heating the Si source to 2000 ℃, much higher than its melting point of 1414 ℃, and grain size larger than 100 μm is realized by changing the temperature of the growth substrates from above to below the melting point of Si. In parallel, simple cell fabrication is also developed. Commercially available carbon nanotube powders are dispersed in water using surfactant, their thin films are fabricated via vacuum filtration. These films are attached to n-Si wafers and power conversion efficiency of 10% is realized. We will combine these technologies toward their practical use.

  • Creation of three-dimensional nano-scale interface at large scale and its application to electric energy storage devices

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (A)

    Project Year :

    2013.10
    -
    2017.03
     

    Noda Suguru, YAMADA Atsuo, YAMADA Yuki, DOKKO Kaoru, MOMMA Toshiyuki, HASEGAWA Kei, QUINTERO RESTREPO Ricardo, LEE Jungho, CHEN Zhongming, KAWABATA Kosuke, NARUBAYASHI Misato, AOI Shigeki, KOWASE Takayuki, HACHIYA Soichiro, HORI Keisuke, MORIKAWA Yusuke, KUZUHARA Soki, HONDA Yoichiro, YAMAGATA Go, OSAWA Toshio

     View Summary

    Toward innovation of electric energy storage using emerging capacitive materials, three-dimensional nanostructured electrodes are developed via simple, rapid, high-yield processes. Si has a ten-times higher theoretical anode capacity than graphite. Several μm-thick, porous Si and Si-Cu alloy anodes are formed directly on Cu current collectors in 1 min from inexpensive and safe sources of their bulks via rapid vapor deposition method. Over 99.6 wt%-pure, submillimeter-long few-wall carbon nanotubes (CNTs) are produced semi-continuously via fluidized-bed method, which are ready for use without purification. CNTs are co-dispersed and co-filtrated with capacitive materials such as activated carbon, lithium cobalt oxide, and graphite to create self-supporting, tens μm-thick films. Such films work as electrodes with line contact with metal wires, and such architecture will minimize the use of heavy current collectors of metals in electrochemical capacitors and rechargeable batteries.

  • Challenge for flame synthesis of single-wall carbon nanotubes

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Challenging Exploratory Research

    Project Year :

    2013.04
    -
    2015.03
     

    NODA Suguru

     View Summary

    Single-wall carbon nanotubes (SWCNTs) are an one dimensional nanomaterial having diameter of ~1 nm and various potential applications. Chemical vapor deposition (CVD) using metal nanoparticles as catalyst is a major synthetic method, however SWCNTs are not practically used due to their very expensive price of ~hundreds of dollars per gram. In this research, we tried to synthesize SWCNTs using the flame synthesis method, which has realized mass production of carbon black particles and fullerenes. We proposed and developed an original flame synthesis method in which ferrocene vapor was decomposed into iron vapor instantly by a premixed flame, iron catalyst nanoparticles were nucleated by instant cooling of the iron vapor to 1000-1400 ℃ by mixing the flame gas with argon gas containing sulfur vapor, and CNTs were synthesized by mixing preheated methane gas with the iron catalyst nanoparticles. Our original method actually yielded SWCNTs.

  • Self-organized growth of structured single-wall carbon nanotubes

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Young Scientists (A)

    Project Year :

    2009
    -
    2011
     

    NODA Suguru

     View Summary

    Many applications are expected for single-wall carbon nanotubes(SWCNTs) owing to their unique 1-dimensional nanostructure and superior properties. However, few of such applications have been realized because their production and implementation technologies are still under development. People come to notice that the interaction between SWCNTs can yield various ensemble morphologies during their growth on substrates. In this research, we enriched both the understanding of the self-organization process fundamentally and the technology base for the direct growth and implementation of structured SWCNTs on device substrates for practical applications.

  • Systematic investigation and systematization of catalytic growth of single-walled carbon nanotubes aided by a combinatorial method

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Young Scientists (A)

    Project Year :

    2006
    -
    2008
     

    NODA Suguru

  • Niドーパント分布場の積極的導入によるアモルファスシリコンの大粒径結晶化

    日本学術振興会  科学研究費助成事業 若手研究(A)

    Project Year :

    2003
    -
    2005
     

    野田 優

     View Summary

    本研究ではアモルファスシリコン(a-Si)上にNiの放射状の分布をつけアニールすることで、Ni誘起結晶化を制御し、中心からの核発生と扇形の結晶成長により、大粒径の多結晶膜を得ることを目指す。昨年度までに申請者が開発したコンビナトリアル手法によりNi量の最適化を進め、膜厚50nmのa-Siに対しNiが膜厚換算数pmで結晶化が促進されることを確認した。
    本年度は、アニール条件の最適化を進めた。既往の研究では、アニールの温度・時間・昇温速度に加え、プレアニールについてもこれらのパラメータが探索され、グループ毎に「レシピ」が作られてきた。しかしa-Siの成膜条件が変わると「レシピ」は使えず、かつこれらの6パラメータの最適化は非常に困難である。そこで、論理的考察により我々は実験パラメータを昇温速度1つに絞り込んだ。即ち、目的温度までの昇温速度を変えることで、これらのパラメータを一度に振れる。また、一度形成した結晶核は、800℃程度までは合一せずに残る為、結晶化初期の構造も保存される。この方法で、0.2℃/minで700℃まで昇温した際、Ni量が10pmから減少する分布場で粒径30μmの結晶粒の形成を確認した。更に、680℃でアニールを止めたサンプルでは、扇形の結晶粒も確認され、目標とした機構による大粒径化を示唆するもので、現在、検証を続けている。
    なお、本研究で利用したコンビナトリアル手法は、別材料でも大きな成果を挙げた。即ち、代表的なナノ材料である単層カーボンナノチューブでは、ナノ粒子触媒の開発が合成法の鍵となるが、本手法により1回の実験での触媒担持条件の最適化を可能とした。

  • Upcycling of Spent Lithium-Ion Batteries Electrodes Towards All-Solid-State Lithium Batteries

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research

    Project Year :

    2022.04
    -
    2024.03
     

  • 使用済みリチウムイオン電池電極の全固体リチウムイオン電池へのアップサイクリング

    日本学術振興会  科学研究費助成事業

    Project Year :

    2021.11
    -
    2024.03
     

    野田 優, SUBRAMANIAN NATARAJAN

  • Mechanistic study on metal chalcogenides catalyzed water splitting for efficient hydrogen production

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research

    Project Year :

    2018.11
    -
    2021.03
     

  • Development of novel large-area synthetic methods of graphene-related atomic layers

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area)

    Project Year :

    2013.06
    -
    2018.03
     

    Kusunoki Michiko, SHINOHARA Hisanori, OHNO Yutaka

     View Summary

    Through deep discussion between synthetic researchers in the synthesis team, (1)Chemical vapor deposition groups attained synthesis of not only large-area but also high-quality graphene consisting of grains of over 5 nm, also did high speed synthesis for practical application, and single layer WS2 on h-BN substrate showing photoluminescence with narrow width of 22 meV, (2)SiC thermal decomposition group succeeded in synthesizing graphene with wafer size and developed the Rapid cooling method for free standing of graphene on SiC substrate, (3) oxidized graphene films deposited on h-BN films was irradiated by methane plasma, which led to high mobility of 4000-7000cm2/Vs, (4)Organic synthesis group attained synthesis of novel graphene ribbons successively and increase of near infrared radiation. Active supplying these samples to researchers in the other teams and foreign countries led to publishing 130 papers due to the collaborating researches.

  • Chirality-Controlled Growth and Separation of Single-Walled Carbon Nanotubes

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research on Priority Areas

    Project Year :

    2007
    -
    2011
     

    MARUYAMA Shigeo, SANO Masato, OKUKBO Tatsuya, NODA Suguru, SHIOMI Junichiro, CHIASHI Shohei

     View Summary

    It is important to obtain chirality-controlled single-walled carbon nanotubes (SWNTs) for SWNT applications. We have developed the growth and separation techniques of the chirality-controlled SWNTs. The SWNT chirality was analyzed by optical and electronic conductivity properties. In order to control the chirality, the catalyst control by using combinatorial method and SAM layer method was performed and the CVD gas effect was investigated. The growth mechanism of horizontally-aligned SWNTs on crystal quartz was elucidated. DGU technique was performed for chirality separation after the growth, and the separation of electronic conductivity (metallic or semiconducting) and chirality was succeeded.

  • Low cost production of crystalline silicon thin films for solar cells by CVD process with closed gas recycling.

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (A)

    Project Year :

    2003
    -
    2005
     

    OKABE Fumio, NODA Suguru

     View Summary

    Large-scale photovoltaic power generation is essential to realize future clean energy systems. The bulk silicon type is promising owing to the abundant resource and excellent stability and safety of silicon. This type now accounts for 80- 90 % of the solar cells. High purity silicon is supplied from the semiconductor industry, and the amount of supply is now limiting the further enhancement of solar cell production. In this project, large-scale, low-cost production of solar cells was studied.
    Silicon substrates are now industrially fabricated by slicing multi/monocrystalline silicon ingots, and an amount of silicon equivalent to about 500 μm thickness is consumed for each substrate. Substitution of substrates for thin films of 10 μm thickness can be a break through for scale enhancement and cost reduction of the solar cell production. We thus studied the epitaxial lift-off (ELO) method, in which a sacrificial layer and a monocrystalline silicon thin film are successively grown on a monocrystalline silicon wafer successively, the thin film and the wafer are separated by etching the sacrificial layer, and the thin film is used as the photovoltaic layer and the wafer is repeatedly used in this ELO process.
    In the ELO process, the epitaxial growth method of the monocrystalline silicon photovoltaic layer is very important. Chemical vapor deposition (CVD) is usually used to grow micrometer-thick epitaxial films, but the utilization ratio of the chlorosilane source gases is small. Chlorosilanes are practically synthesized by reacting metallurgical grade silicon with hydrogen chloride. By recycling the outlet gas of CVD reactor into the reactor of chlorosilane synthesis, an ideal process can be realized in which metallurgical grade silicon is converted into monocrystalline silicon thin films with a minimal material loss. Literature survey of the current production process of chlorosilanes and experimental investigations of the reaction rate processes of chlorosilane synthesis and Si-CVD were performed in parallel, and feasibility of this "CVD process with closed gas recycling" was examined. But the problems came out such as possible contaminations into silicon thin films and degradation of the sacrificial layer used in ELO process. On the other hand, physical vapor deposition (PVD) was suggested effective in the ELO process. Based on a new concept of rapid vapor deposition (RVD), a silicon epitaxial growth rate as large as 10μm/min was confirmed at the substrate temperatures of 800-1000℃.
    By coupling ELO and RVD processes, we succeeded to lift-off 5-10μm thick monocrystalline silicon thin films of a limited areal size. This is an achievement leading to the solution of the high-purity silicon shortage and the realization of large-scale, low-cost solar cell production.

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Industrial Property Rights

  • 自立膜、積層シート、及び自立膜の製造方法

    特許第7424652号

    野田 優, 宗像 瀬文

    Patent

    J-GLOBAL

  • 二次電池用負極、二次電池、および二次電池用負極の製造方法

    特許第7411966号

    野田 優, 堀 圭佑, 前 智太郎, 橋爪 裕太

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  • ナノカーボン材料製造装置及びナノカーボン材料の製造方法

    野田 優, 大沢 利男, 金 東榮, 羽場 英介, 上田 俊輔

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  • シリコン膜およびリチウム二次電池

    野田 優, 諸隈 慎吾, 山本 武継

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  • 金属埋め込み方法及び凹部に金属を堆積させるための装置

    特許第4723678号

    野田 優, 高嶋 智史

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  • カーボンナノチューブ及び水素の同時製造方法、並びに、カーボンナノチューブ及び水素の同時製造装置

    野田 優, 金 東榮, 大沢 利男, 杉目 恒志, 長谷川 馨, 羽場 英介

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  • 化学気相成長装置、化学気相成長方法

    野田 優, 古市 考次

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  • 単結晶薄膜の製造方法及びその単結晶薄膜デバイス

    野田 優

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  • カーボンナノチューブデバイス、ならびに、その製造方法

    特許第4558735号

    野田 優

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  • カーボンナノチューブ形成方法

    野田 優, 古市 考次

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  • 面発光装置

    野田 優, 古市 考次, 白鳥 洋介

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  • ハイブリッド反応モデルを用いたシミュレーションシステムまたはシミュレーション方法。

    特許第4449472号

    末富 英一, 深沢 孝二, 霜垣 幸浩, 杉山 正和, 野田 優

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  • 薄膜作製装置

    特許第4405973号

    全 基栄, 坂本 仁志, 野田 優

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  • フィールドエミッション装置、ならびに、その製造方法

    野田 優, 古市 考次, 白鳥 洋介, 辻 佳子, 杉目 恒志

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  • カーボンナノチューブの製造方法及びカーボンナノチューブ製造装置

    野田 優, 杉目 恒志, 山口 由岐夫, 大沢 利男, 筧 和憲, 長谷川 馨, 金 東榮

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  • 金属埋め込み方法及び凹部に金属を堆積させるための装置

    野田 優, 高嶋 智史

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  • カーボンナノチューブの製造方法

    野田 優, 杉目 恒志, 山口 由岐夫

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  • 材料設計支援方法ならびにそのシステム

    特許第4047581号

    小宮山 宏, 山口 由岐夫, 野田 優

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  • 薄膜作製装置

    全 基栄, 坂本 仁志, 野田 優

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  • 薄膜作製方法及び薄膜作製装置

    特許第3937411号

    坂本 仁志, 野田 優

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  • 磁気記録媒体及びその製造方法

    野田 優

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  • カーボンナノチューブデバイス及びカーボンナノチューブデバイスの製造方法

    野田 優, 丸山 茂夫

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  • カーボンナノチューブデバイス、ならびに、その製造方法

    野田 優

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  • 薄膜作製方法及び薄膜作製装置

    坂本 仁志, 野田 優

    Patent

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  • ハイブリッド反応モデルを用いたシミュレーションシステムまたはシミュレーション方法。

    末富 英一, 深沢 孝二, 霜垣 幸浩, 杉山 正和, 野田 優

    Patent

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  • 単結晶薄膜の製造方法及びその単結晶薄膜デバイス

    野田 優

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  • 薄膜作製方法及び薄膜作製装置

    坂本 仁志, 野田 優

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  • 錐体型微小構造体及びその製造方法

    辻 佳子, 野田 優

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  • ナノ粒子デバイス及びナノ粒子デバイスの製造方法

    野田 優

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  • 目的膜の製造方法及びそれによって得られた目的膜並びに複層構造物

    小宮山 宏, 野田 優, 辻 佳子

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Syllabus

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Sub-affiliation

  • Faculty of Science and Engineering   Graduate School of Advanced Science and Engineering

Research Institute

  • 2022
    -
    2024

    Research Organization for Open Innovation Strategy   Concurrent Researcher

  • 2022
    -
    2024

    Waseda Research Institute for Science and Engineering   Concurrent Researcher

  • 2022
    -
    2024

    Waseda Center for a Carbon Neutral Society   Concurrent Researcher

Internal Special Research Projects

  • 革新的太陽電池の開発と評価の両輪の実践と、萌芽技術の社会実装学の開拓

    2018   TEAH, Heng Ti, 大沢 利男, 杉目 恒志, 石嶋 直也, 須藤 南美

     View Summary

    本課題では、薄膜型の軽量性・柔軟性・設置容易性と、結晶Si型の高効率・長寿命を兼ね備えた、結晶Si膜太陽電池の簡易・高速製造技術の、開発と評価の両輪を進めた。これまでCNT-Siヘテロ接合で発電効率10.4%だったところ、Si表面のパッシベーションとPEDOT:PSS塗布・ヘテロ接合形成で12.9%まで向上した。また、PEDOT:PSS-Siセル表面へのAgの1分蒸着による櫛形電極形成で、セルサイズを0.03 cm2から4 cm2へと100倍超に拡大しつつ発電効率7.5%を得た。加えて、独自の融液蒸着-その場結晶化による結晶Si膜製造とヘテロ接合の塗布形成の全体プロセスのLCA評価に着手した。

  • 3次元ナノ界面の大規模創製と、蓄電デバイス電極への展開

    2013  

     View Summary

    ①シリコン系合金多孔質厚膜の急速蒸着およびポーラス電極の蓄電応用検討・シリコン多孔質厚膜の急速蒸着と微細構造制御:我々はシリコン蒸着源を2000℃以上と高温にすることで、従来より数桁高い10 &micro;m/min前後の蒸着速度を実現している。本研究では、充放電サイクル後に理想的な定常構造を得るべく初期構造を作り込んだ。即ち、基板温度400℃以下にて非晶質膜を得、柱状構造の太さ、空隙、膜密度を制御した。更に、熱アニールにより非晶質シリコンの結晶化を防ぎつつ、シリコンと銅の相互拡散層を形成して密着性を向上した。・単一蒸着源による合金多孔質厚膜の急速蒸着:シリコンは理論容量が非常に高く、他金属と複合化しても十分な容量を保てる。銅と共蒸着して銅集電極を3次元化し、劣化抑制と導電性向上を試みた。銅はシリコンと蒸気圧が近いため、単一のルツボにともに仕込んで共蒸着し、走査型電子顕微鏡(SEM)-エネルギー分散型X線分光法(EDS)により組成傾斜構造を確認した。・充放電特性評価:充放電評価装置を導入し、上記のサンプルの充放電特性を評価し、サイクル特性の向上を確認した。②長尺CNTの連続合成、良導性CNTスポンジの開発、およびソフト電極の蓄電応用検討・流動層法での長尺CNTの層数制御:我々は独自のCVD触媒担持法を用い、平均3層と細く400 &micro;m程度と長尺な数層CNTの流動層合成を実現、バインダーレスで良導性の自己組織化ネットワークの自立膜を実現している。CNTの層数が少ないほど自立膜の導電性が向上するが、一方で、二層以上では内層で導電、外層に官能基導入と、機能分担ができるため、CVD担持法に加え液相含浸担持法により触媒の構造制御とCNTの層数制御を進めた。・CNTスポンジの作製基礎技術の開発:CNTを溶液に分散しろ過すると、ネットワーク状膜やスポンジ構造を実現できる。キャパシタ・電池電極利用では種々の活物質と複合化するが、CNTと活物質を同時にろ過するか、CNT膜を形成してから複合化するか、大きく二つのルートがある。目的に応じて分散・膜形成手法を選択できるよう、基礎技術を培った。・長尺CNTと活性炭の複合化による電気化学キャパシタ電極の開発:活性炭は高い比表面積を有しキャパシタの活物質に有効だが、導電性に乏しいため通常は導電助剤とバインダーを用いて金属集電体に塗布し電極化する。一方で我々の数層CNTはバインダーフリーで自立膜を形成でき、導電性が高く、集電極としても機能し得る。バインダーフリーでCNTと活性炭の複合体を作製、キャパシタ電極特性の評価を進め、開発した活性炭-CNT複合電極が実際に金属集電体フリーの軽量・高容量電極として動作することを確認した。・長尺CNTと二酸化マンガンの複合化による電気化学キャパシタ電極の開発:酸化マンガンは、酸化還元反応により高い容量を有すが、導電性に乏しいことが課題である。そこで、我々の数層CNTの分散・ろ過で作製したCNTスポンジを電極とし、二酸化マンガンをCNTスポンジ中に電析し、複合電極を作製した。電気化学評価を行い、低レートでは活性炭-CNT複合電極と同様の高容量が100 μm程度と十分に厚い電極で得られることを確認した。