2022/12/08 更新

写真a

ノダ スグル
野田 優
Scopus 論文情報  
論文数: 0  Citation: 0  h-index: 28

Citation Countは当該年に発表した論文の被引用数

所属
理工学術院 先進理工学部
職名
教授
ホームページ
プロフィール
1994.03 東京大学 工学部 化学工学科 卒業
1996.03 東京大学 大学院工学系研究科 化学システム工学専攻 修士課程修了
1999.03 東京大学 大学院工学系研究科 化学システム工学専攻 博士課程修了・博士(工学)取得
---
1999.04 東京大学 大学院工学系研究科 助手(化学システム工学専攻)
2007.04 〃 助教(化学システム工学専攻)
2007.06 〃 准教授(化学システム工学専攻)
2012.09 早稲田大学 理工学術院 教授、現在に至る
2009.10-2013.03 JST さきがけ研究員・併任

他学部・他研究科等兼任情報

  • 理工学術院   大学院先進理工学研究科

学内研究所・附属機関兼任歴

  • 2021年
    -
    2022年

    リサーチイノベ オープンイノベーション推進セクション   兼任センター員

  • 2020年
    -
    2022年

    理工学術院総合研究所   兼任研究員

学歴

  •  
    -
    1999年

    東京大学   大学院工学系研究科   化学システム工学専攻  

  •  
    -
    1999年

    東京大学   大学院工学系研究科   化学システム工学専攻  

  •  
    -
    1994年

    東京大学   工学部   化学工学科  

学位

  • 東京大学   博士(工学)

経歴

  • 2012年09月
    -
    継続中

    早稲田大学 理工学術院 教授

  • 2007年06月
    -
    2012年08月

    東京大学 大学院工学系研究科 准教授

  • 2007年04月
    -
    2007年06月

    東京大学 大学院工学系研究科 助教

  • 1999年04月
    -
    2007年03月

    東京大学 大学院工学系研究科 助手

所属学協会

  • 2017年10月
    -
    2023年09月

    日本学術会議(連携会員)

  •  
     
     

    日本工学アカデミー

  •  
     
     

    炭素材料学会

  •  
     
     

    フラーレン・ナノチューブ・グラフェン学会

  •  
     
     

    Materials Research Society

  •  
     
     

    応用物理学会

  •  
     
     

    化学工学会

▼全件表示

 

研究分野

  • 反応工学、プロセスシステム工学

  • ナノバイオサイエンス

研究キーワード

  • 材料プロセス工学、カーボンナノチューブ、グラフェン、シリコン薄膜、化学気相成長法、物理蒸着法

論文

  • 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年02月  [査読有り]

    DOI

    Scopus

    11
    被引用数
    (Scopus)
  • Dos and don’ts in screening water splitting electrocatalysts

    Sengeni Anantharaj, Suguru Noda

    Energy Advances    2022年

     概要を見る

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

    DOI

  • 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年

    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年01月

     概要を見る

    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

    Scopus

    14
    被引用数
    (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年

     概要を見る

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

    DOI

    Scopus

    4
    被引用数
    (Scopus)
  • 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 & Environmental Science   15 ( 4 ) 1461 - 1478  2022年

     概要を見る

    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

    Scopus

    6
    被引用数
    (Scopus)
  • 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年12月

    DOI

    Scopus

    2
    被引用数
    (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年12月

    DOI

    Scopus

    8
    被引用数
    (Scopus)
  • 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年11月  [査読有り]

    DOI

    Scopus

    4
    被引用数
    (Scopus)
  • The Significance of Properly Reporting Turnover Frequency in Electrocatalysis Research

    Sengeni Anantharaj, Pitchiah Esakki Karthik, Suguru Noda

    Angewandte Chemie International Edition    2021年09月  [査読有り]

    担当区分:最終著者

    DOI

    Scopus

    60
    被引用数
    (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    2021年09月  [査読有り]

    担当区分:最終著者, 責任著者

    DOI

    Scopus

    1
    被引用数
    (Scopus)
  • 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年08月  [査読有り]

    担当区分:最終著者, 責任著者

    DOI

    Scopus

    5
    被引用数
    (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年06月  [査読有り]

    DOI

    Scopus

    5
    被引用数
    (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    2021年05月  [査読有り]

    担当区分:最終著者, 責任著者

    DOI

    Scopus

    8
    被引用数
    (Scopus)
  • 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年05月  [査読有り]

    担当区分:最終著者, 責任著者

    DOI

    Scopus

    4
    被引用数
    (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年04月  [査読有り]

    担当区分:責任著者

    DOI

    Scopus

    2
    被引用数
    (Scopus)
  • 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年03月  [査読有り]

    担当区分:責任著者

    DOI

    Scopus

    94
    被引用数
    (Scopus)
  • 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年02月  [査読有り]

    DOI

    Scopus

    2
    被引用数
    (Scopus)
  • 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年02月  [査読有り]

    担当区分:最終著者

    DOI

    Scopus

    11
    被引用数
    (Scopus)
  • “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年02月  [査読有り]

    担当区分:最終著者, 責任著者

    DOI

    Scopus

    206
    被引用数
    (Scopus)
  • 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年01月  [査読有り]

    DOI

    Scopus

    16
    被引用数
    (Scopus)
  • 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年01月  [査読有り]

    担当区分:責任著者

    DOI

    Scopus

    93
    被引用数
    (Scopus)
  • 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年01月  [査読有り]

    担当区分:最終著者, 責任著者

    DOI

    Scopus

    13
    被引用数
    (Scopus)
  • High-performance solution-based silicon heterojunction solar cells using carbon nanotube with polymeric acid doping

    Rongbin Xie, Hisashi Sugime, Suguru Noda

    Carbon    2021年01月  [査読有り]

    担当区分:最終著者, 責任著者

    DOI

    Scopus

    5
    被引用数
    (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年12月  [査読有り]

    担当区分:最終著者, 責任著者

    DOI

    Scopus

    6
    被引用数
    (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年12月  [査読有り]

    担当区分:最終著者, 責任著者

    DOI PubMed

    Scopus

    24
    被引用数
    (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年11月  [査読有り]

    担当区分:最終著者, 責任著者

    DOI

    Scopus

    11
    被引用数
    (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年10月  [査読有り]

    担当区分:最終著者, 責任著者

    DOI

    Scopus

    33
    被引用数
    (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年10月  [査読有り]

    担当区分:最終著者, 責任著者

    DOI

    Scopus

    11
    被引用数
    (Scopus)
  • Nanotubes make battery lighter and safer

    Kentaro Kaneko, Keisuke Hori, Suguru Noda

    Carbon   167   596 - 600  2020年10月  [査読有り]

    担当区分:最終著者, 責任著者

    DOI

    Scopus

    3
    被引用数
    (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年08月  [査読有り]

    担当区分:最終著者, 責任著者

    DOI

    Scopus

    13
    被引用数
    (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年06月  [査読有り]

    担当区分:最終著者, 責任著者

    DOI PubMed

    Scopus

    60
    被引用数
    (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年06月  [査読有り]

    DOI

    Scopus

    7
    被引用数
    (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年05月  [査読有り]

    DOI

    Scopus

    37
    被引用数
    (Scopus)
  • Appropriate Use of Electrochemical Impedance Spectroscopy in Water Splitting Electrocatalysis

    Sengeni Anantharaj, Suguru Noda

    ChemElectroChem   7 ( 10 ) 2297 - 2308  2020年05月  [査読有り]

    担当区分:最終著者

    DOI

    Scopus

    72
    被引用数
    (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年05月  [査読有り]

    担当区分:最終著者, 責任著者

    DOI

    Scopus

    23
    被引用数
    (Scopus)
  • Nickel selenides as pre-catalysts for electrochemical oxygen evolution reaction: A review

    Sengeni Anantharaj, Suguru Noda

    International Journal of Hydrogen Energy    2020年05月  [査読有り]

    担当区分:最終著者, 責任著者

    DOI

    Scopus

    68
    被引用数
    (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年04月  [査読有り]

    DOI

    Scopus

    10
    被引用数
    (Scopus)
  • 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年  [査読有り]

    担当区分:最終著者

    DOI

    Scopus

    15
    被引用数
    (Scopus)
  • Progress in nickel chalcogenides electrocatalyzed hydrogen evolution reaction

    Sengeni Anantharaj, Subrata Kundu, Suguru Noda

    Journal of Materials Chemistry A   8 ( 8 ) 4174 - 4192  2020年  [査読有り]

    担当区分:最終著者, 責任著者

    DOI

    Scopus

    118
    被引用数
    (Scopus)
  • High-energy density LixSi-S full cell based on 3D current collector of few-wall carbon nanotube sponge

    Keisuke Hori, Yuki Yamada, Toshiyuki Momma, Suguru Noda

    Carbon   161   612 - 621  2020年  [査読有り]

    担当区分:最終著者, 責任著者

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

    S. Anantharaj, S. Noda

    Small   16 ( 2 ) 1905779  2020年  [査読有り]

    担当区分:最終著者, 責任著者

    DOI PubMed

    Scopus

    233
    被引用数
    (Scopus)
  • Life cycle greenhouse gas emissions of long and pure carbon nanotube synthesized via on-substrate and fluidized-bed chemical vapor deposition

    H.Y. Teah, T. Sato, K. Namiki, M. Asaka, K. Feng, S. Noda

    ACS Sustainable Chem. Eng.   8 ( 4 ) 1730 - 1740  2020年  [査読有り]

    担当区分:最終著者, 責任著者

    DOI

    Scopus

    16
    被引用数
    (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年11月  [査読有り]

    DOI PubMed

    Scopus

    8
    被引用数
    (Scopus)
  • 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  2019年10月  [査読有り]

    DOI

    Scopus

    8
    被引用数
    (Scopus)
  • 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年08月  [査読有り]

    担当区分:最終著者, 責任著者

    DOI PubMed

    Scopus

    12
    被引用数
    (Scopus)
  • Stability of chemically doped nanotube-silicon heterojunction solar cells: Role of oxides at the carbon-silicon interface

    D. Tune, H. Shirae, V. Lami, R. Headrick, M. Pasquali, Y. Vaynzof, S. Noda, E. Hobbie, B. Flavel

    ACS Applied Energy Materials   2 ( 8 ) 5925 - 5923  2019年07月  [査読有り]

    DOI

    Scopus

    9
    被引用数
    (Scopus)
  • A semi-transparent nitride photoanode responsive up to 600 nm based on a carbon nanotube thin film electrode

    D. Akagi, Y. Kageshima, Y. Hashizume, S. Aoi, Y. Sasaki, H. Kaneko, T. Higashi, T. Hisatomi, M. Katayama, T. Minegishi, S. Noda, K. Domen

    ChemPhotoChem   3   521 - 524  2019年04月  [査読有り]

    DOI

    Scopus

    10
    被引用数
    (Scopus)
  • 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年03月  [査読有り]

    担当区分:最終著者, 責任著者

    DOI

    Scopus

    10
    被引用数
    (Scopus)
  • 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年02月  [査読有り]

    担当区分:最終著者, 責任著者

    DOI

    Scopus

    2
    被引用数
    (Scopus)
  • Volumetric discharge capacity 1 Ah cm-3 realized by sulfur in carbon nanotube sponge cathode

    K. Hori, K. Hasegawa, T. Momma, S. Noda

    J. Phys. Chem. C   123 ( 7 ) 3951 - 3958  2019年01月  [査読有り]

    担当区分:最終著者, 責任著者

    DOI

    Scopus

    9
    被引用数
    (Scopus)
  • Carbon nanotubes and related nanomaterials: critical advances and challenges for synthesis towards mainstream commercial applications

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

    ACS Nano   12 ( 12 ) 111756 - 111784  2018年12月  [査読有り]

    DOI

    Scopus

    271
    被引用数
    (Scopus)
  • 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年09月  [査読有り]

     概要を見る

    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.

    DOI

    Scopus

    25
    被引用数
    (Scopus)
  • Resettable heterogeneous catalyst: (re)generation and (re)adsorption of Ni nanoparticles for repeated synthesis of carbon nanotubes on Ni-Al-O thin films

    B. Liang, E. Yi, T. Sato, S. Noda, K. Sun, D. Jia, Y. Zhou, R. M. Laine

    ACS Applied Nano Materials    2018年09月  [査読有り]

    DOI

    Scopus

  • 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年06月  [査読有り]

    DOI PubMed

  • 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年05月  [査読有り]

    DOI

    Scopus

    21
    被引用数
    (Scopus)
  • Carbon nanotube web with carboxylated polythiophene “assist” for high-performance battery electrodes

    Y. H. Kwon, J. J. Park, L. M. Housel, K. Minnici, G. Zhang, S. R. Lee, S. W. Lee, Z. Chen, S. Noda, E. S. Takeuchi, K. J. Takeuchi, A. C. Marschilok, E. Reichmanis

    ACS Nano   12 ( 4 ) 3126 - 3139  2018年04月  [査読有り]

    DOI

    Scopus

    39
    被引用数
    (Scopus)
  • 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年04月  [査読有り]

     概要を見る

    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.

    DOI

    Scopus

  • 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年04月

     概要を見る

    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.

    DOI

    Scopus

    21
    被引用数
    (Scopus)
  • 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年

     概要を見る

    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.

    DOI

    Scopus

    27
    被引用数
    (Scopus)
  • 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年

     概要を見る

    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.

    DOI

    Scopus

    8
    被引用数
    (Scopus)
  • 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年  [査読有り]

     概要を見る

    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.

    DOI

    Scopus

    4
    被引用数
    (Scopus)
  • 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年09月  [査読有り]

     概要を見る

    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 >= 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.

    DOI

    Scopus

    15
    被引用数
    (Scopus)
  • 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年07月

     概要を見る

    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.

    DOI

    Scopus

    2
    被引用数
    (Scopus)
  • 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年04月  [査読有り]

     概要を見る

    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 <= 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 >= 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.

    DOI

    Scopus

    7
    被引用数
    (Scopus)
  • 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年03月  [査読有り]

     概要を見る

    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

    DOI

    Scopus

    9
    被引用数
    (Scopus)
  • Remarkably air- and moisture-stable hole-doped carbon nanotube films by a 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

    Appl. Phys. Express   10   035101  2017年02月  [査読有り]

  • 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年01月  [査読有り]

     概要を見る

    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.

    DOI

    Scopus

    205
    被引用数
    (Scopus)
  • 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年07月  [査読有り]

     概要を見る

    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.

    DOI

    Scopus

    27
    被引用数
    (Scopus)
  • 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年02月  [査読有り]

     概要を見る

    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.

    DOI

    Scopus

    34
    被引用数
    (Scopus)
  • 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年01月  [査読有り]

     概要を見る

    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.

    DOI

    Scopus

    10
    被引用数
    (Scopus)
  • 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年  [査読有り]

     概要を見る

    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.

    DOI

    Scopus

    16
    被引用数
    (Scopus)
  • 50-100-μm-thick pseudocapacitive electrodes of MnO2 nanoparticles uniformly electrodeposited in carbon nanotube papers

    M. Narubayashi, Z. Chen, K. Hasegawa, S. Noda

    RSC Advances   6 ( 47 ) 41496 - 41505  2016年  [査読有り]

     概要を見る

    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 μm-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 μm, 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 Ftotal gelectrode−1, volumetric capacitance of 131 and 56 Ftotal 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.

    DOI

    Scopus

    13
    被引用数
    (Scopus)
  • Rapid vapour deposition and in situ melt crystallization for 1-min fabrication of 10-μm-thick crystalline silicon films with a lateral grain size of over 100 μm

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

    CrystEngComm   18 ( 19 ) 3404 - 3410  2016年  [査読有り]

     概要を見る

    We developed a film deposition method which yielded continuous polycrystalline Si films with large lateral grain sizes of over 100 μm and thicknesses of ∼10 μm in 1 min on growth substrates other than silicon wafers in a single-step process. The silicon source is heated to ∼2000 °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 μm-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.

    DOI

    Scopus

    6
    被引用数
    (Scopus)
  • 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年  [査読有り]

     概要を見る

    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.

    DOI

    Scopus

    31
    被引用数
    (Scopus)
  • 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年  [査読有り]

     概要を見る

    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.

    DOI

    Scopus

    1
    被引用数
    (Scopus)
  • 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年09月  [査読有り]

     概要を見る

    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

    DOI

    Scopus

    16
    被引用数
    (Scopus)
  • 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年09月  [査読有り]

     概要を見る

    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.

    DOI

    Scopus

    21
    被引用数
    (Scopus)
  • 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年07月  [査読有り]

     概要を見る

    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.

    DOI

    Scopus

    15
    被引用数
    (Scopus)
  • 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年05月  [査読有り]

     概要を見る

    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.

    DOI

    Scopus

    109
    被引用数
    (Scopus)
  • 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年02月  [査読有り]

     概要を見る

    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.

    DOI

    Scopus

    28
    被引用数
    (Scopus)
  • Simple and engineered process yielding carbon nanotube arrays with 1.2×1013 cm-2 wall density on conductive underlayer at 400 °C

    N. Na, D.Y.Kim, Y.-G. So, Y. Ikuhara, S. Noda

    Carbon   81   773 - 781  2015年01月  [査読有り]

    DOI

    Scopus

    24
    被引用数
    (Scopus)
  • One-minute deposition of micrometre-thick porous Si anodes for lithium ion batteries

    Jungho Lee, Suguru Noda

    RSC ADVANCES   5 ( 4 ) 2938 - 2946  2015年  [査読有り]

     概要を見る

    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.

    DOI

    Scopus

    7
    被引用数
    (Scopus)
  • 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年  [査読有り]

     概要を見る

    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)).

    DOI

    Scopus

    11
    被引用数
    (Scopus)
  • 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年12月  [査読有り]

     概要を見る

    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.

    DOI

    Scopus

    34
    被引用数
    (Scopus)
  • One-step sub-10 μm patterning of carbon-nanotube thin films for transparent conductor applications

    N. Fukaya, D.Y. Kim, S. Kishimoto, S. Noda, Y. Ohno

    ACS Nano   8 ( 4 ) 3285 - 3293  2014年04月  [査読有り]

    DOI

    Scopus

    71
    被引用数
    (Scopus)
  • 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年  [査読有り]

     概要を見る

    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.

    DOI

    Scopus

    31
    被引用数
    (Scopus)
  • 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年08月  [査読有り]

     概要を見る

    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.

    DOI

    Scopus

    20
    被引用数
    (Scopus)
  • 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年07月  [査読有り]

     概要を見る

    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.

    DOI

    Scopus

    30
    被引用数
    (Scopus)
  • 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年05月  [査読有り]

     概要を見る

    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.

    DOI

    Scopus

    9
    被引用数
    (Scopus)
  • 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年04月  [査読有り]

     概要を見る

    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 <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.

    DOI

    Scopus

    34
    被引用数
    (Scopus)
  • 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年02月  [査読有り]

    DOI

    Scopus

    32
    被引用数
    (Scopus)
  • 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年01月  [査読有り]

     概要を見る

    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.

    DOI

    Scopus

    119
    被引用数
    (Scopus)
  • 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年12月  [査読有り]

     概要を見る

    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.

    DOI

    Scopus

    15
    被引用数
    (Scopus)
  • 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年11月  [査読有り]

     概要を見る

    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.

    DOI

    Scopus

    58
    被引用数
    (Scopus)
  • 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年09月  [査読有り]

     概要を見る

    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

    DOI

    Scopus

  • 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年08月  [査読有り]

     概要を見る

    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.

    DOI

    Scopus

    16
    被引用数
    (Scopus)
  • 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年05月  [査読有り]

     概要を見る

    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.

    DOI

    Scopus

    60
    被引用数
    (Scopus)
  • 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年05月  [査読有り]

     概要を見る

    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]

    DOI

    Scopus

    9
    被引用数
    (Scopus)
  • Millimeter-Tall Single-Walled Carbon Nanotubes Rapidly Grown with and without Water

    Kei Hasegawa, Suguru Noda

    ACS NANO   5 ( 2 ) 975 - 984  2011年02月  [査読有り]

     概要を見る

    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.

    DOI

    Scopus

    105
    被引用数
    (Scopus)
  • 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年09月  [査読有り]

     概要を見る

    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.

    DOI

    Scopus

    2
    被引用数
    (Scopus)
  • 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年08月  [査読有り]

     概要を見る

    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.

    DOI

    Scopus

    4
    被引用数
    (Scopus)
  • 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年08月  [査読有り]

     概要を見る

    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

    DOI

    Scopus

    27
    被引用数
    (Scopus)
  • Millimeter-tall single-walled carbon nanotube forests grown from ethanol

    Hisashi Sugime, Suguru Noda

    CARBON   48 ( 8 ) 2203 - 2211  2010年07月  [査読有り]

     概要を見る

    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 (>= 10 s). Thick Co catalytic layers (>= 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.

    DOI

    Scopus

    54
    被引用数
    (Scopus)
  • Microstructures and transparent conducting properties of self-organized networks of single-walled carbon nanotubes

    Ketpreechasawat Suarpa, 杉目 恒志, 白鳥 洋介, 野田 優

    化学工学会 研究発表講演要旨集   2010   549 - 549  2010年

    DOI CiNii

  • 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年  [査読有り]

     概要を見る

    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

    DOI

    Scopus

    22
    被引用数
    (Scopus)
  • Diameter Increase in Millimeter-Tall Vertically Aligned Single-Walled Carbon Nanotubes during Growth

    Kei Hasegawa, Suguru Noda

    APPLIED PHYSICS EXPRESS   3 ( 4 ) 045103  2010年  [査読有り]

     概要を見る

    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

    DOI

    Scopus

    38
    被引用数
    (Scopus)
  • 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年11月  [査読有り]

     概要を見る

    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.

    DOI

    Scopus

    7
    被引用数
    (Scopus)
  • 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年06月  [査読有り]

     概要を見る

    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.

    DOI

    Scopus

    7
    被引用数
    (Scopus)
  • 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年03月  [査読有り]

     概要を見る

    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.

    DOI

    Scopus

    40
    被引用数
    (Scopus)
  • Thickness-gradient dependent Raman enhancement in silver island films

    T. W. H. Oates, S. Noda

    APPLIED PHYSICS LETTERS   94 ( 5 ) 053106  2009年02月  [査読有り]

     概要を見る

    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.

    DOI

    Scopus

    17
    被引用数
    (Scopus)
  • 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年  [査読有り]

     概要を見る

    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年  [査読有り]

     概要を見る

    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.

    DOI

    Scopus

    2
    被引用数
    (Scopus)
  • 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年01月  [査読有り]

     概要を見る

    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.

    DOI

    Scopus

    98
    被引用数
    (Scopus)
  • 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年11月  [査読有り]

     概要を見る

    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.

    DOI

    Scopus

    37
    被引用数
    (Scopus)
  • 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年11月  [査読有り]

     概要を見る

    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.

    DOI

    Scopus

    10
    被引用数
    (Scopus)
  • 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年08月  [査読有り]

     概要を見る

    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.

    DOI

    Scopus

    68
    被引用数
    (Scopus)
  • 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年08月  [査読有り]

     概要を見る

    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 ('grasses'), 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.

    DOI

    Scopus

    21
    被引用数
    (Scopus)
  • 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年06月  [査読有り]

     概要を見る

    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.

    DOI

    Scopus

    15
    被引用数
    (Scopus)
  • 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年04月  [査読有り]

     概要を見る

    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.

    DOI

    Scopus

    9
    被引用数
    (Scopus)
  • 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年04月

     概要を見る

    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.

    DOI

    Scopus

    25
    被引用数
    (Scopus)
  • 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年

    DOI CiNii

  • 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年

    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年11月  [査読有り]

     概要を見る

    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.

    DOI

    Scopus

    6
    被引用数
    (Scopus)
  • 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年05月  [査読有り]

     概要を見る

    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.

    DOI

    Scopus

    199
    被引用数
    (Scopus)
  • 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年05月  [査読有り]

     概要を見る

    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.

    DOI

    Scopus

    2
    被引用数
    (Scopus)
  • 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年

    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年09月  [査読有り]

     概要を見る

    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.

    DOI

    Scopus

    23
    被引用数
    (Scopus)
  • 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年07月  [査読有り]

     概要を見る

    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.

    DOI

    Scopus

    94
    被引用数
    (Scopus)
  • 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年02月  [査読有り]

     概要を見る

    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.

    DOI

    Scopus

    66
    被引用数
    (Scopus)
  • 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年  [査読有り]

     概要を見る

    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.

    DOI

    Scopus

    29
    被引用数
    (Scopus)
  • 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年11月  [査読有り]

     概要を見る

    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.

    DOI

    Scopus

    4
    被引用数
    (Scopus)
  • Growth mode during initial stage of chemical vapor deposition

    Y Kajikawa, S Noda

    APPLIED SURFACE SCIENCE   245 ( 1-4 ) 281 - 289  2005年05月  [査読有り]

     概要を見る

    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. © 2004 Elsevier B.V. All rights reserved.

    DOI

    Scopus

    43
    被引用数
    (Scopus)
  • 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年04月  [査読有り]

     概要を見る

    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.

    DOI

    Scopus

    49
    被引用数
    (Scopus)
  • Structuring knowledge on nanomaterials processing

    H Komiyama, Y Yamaguchi, S Noda

    CHEMICAL ENGINEERING SCIENCE   59 ( 22-23 ) 5085 - 5090  2004年11月  [査読有り]

     概要を見る

    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.

    DOI

    Scopus

    5
    被引用数
    (Scopus)
  • 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年10月  [査読有り]

     概要を見る

    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.

    DOI

    Scopus

    5
    被引用数
    (Scopus)
  • 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年09月  [査読有り]

     概要を見る

    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).

    DOI

    Scopus

    9
    被引用数
    (Scopus)
  • 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年09月  [査読有り]

     概要を見る

    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.

    DOI

    Scopus

    5
    被引用数
    (Scopus)
  • 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年08月  [査読有り]

     概要を見る

    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.

    DOI

    Scopus

    9
    被引用数
    (Scopus)
  • 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年08月  [査読有り]

     概要を見る

    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.

    DOI

    Scopus

    8
    被引用数
    (Scopus)
  • 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年06月  [査読有り]

     概要を見る

    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.

    DOI

    Scopus

    22
    被引用数
    (Scopus)
  • 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年06月  [査読有り]

     概要を見る

    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.

    DOI

    Scopus

    18
    被引用数
    (Scopus)
  • 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年03月  [査読有り]

     概要を見る

    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.

    DOI

    Scopus

    17
    被引用数
    (Scopus)
  • 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年03月  [査読有り]

     概要を見る

    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.

    DOI

    Scopus

    20
    被引用数
    (Scopus)
  • 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年  [査読有り]

     概要を見る

    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.

    DOI

    Scopus

    11
    被引用数
    (Scopus)
  • 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年11月  [査読有り]

     概要を見る

    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.

    DOI

    Scopus

    103
    被引用数
    (Scopus)
  • 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年11月  [査読有り]

     概要を見る

    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.

    DOI

    Scopus

    15
    被引用数
    (Scopus)
  • 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年09月  [査読有り]

     概要を見る

    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 <111> 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.

    DOI

    Scopus

    19
    被引用数
    (Scopus)
  • 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年09月  [査読有り]

     概要を見る

    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.

    DOI

    Scopus

    35
    被引用数
    (Scopus)
  • 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年06月  [査読有り]

     概要を見る

    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.

    DOI

    Scopus

    22
    被引用数
    (Scopus)
  • Mechanisms controlling preferred orientation of chemical vapour deposited polycrystalline films

    Y Kajikawa, S Noda, H Komiyama

    POLYCRYSTALLINE SEMICONDUCTORS VII, PROCEEDINGS   93   411 - 416  2003年  [査読有り]

     概要を見る

    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年08月  [査読有り]

     概要を見る

    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

    53
    被引用数
    (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年05月  [査読有り]

     概要を見る

    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

    76
    被引用数
    (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年05月  [査読有り]

     概要を見る

    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

    45
    被引用数
    (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年05月  [査読有り]

     概要を見る

    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
    被引用数
    (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年05月  [査読有り]

     概要を見る

    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

    51
    被引用数
    (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年03月  [査読有り]

     概要を見る

    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
    被引用数
    (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年11月  [査読有り]

     概要を見る

    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
    被引用数
    (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年09月  [査読有り]

     概要を見る

    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

    164
    被引用数
    (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年06月  [査読有り]

     概要を見る

    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年03月  [査読有り]

     概要を見る

    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
    被引用数
    (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年03月  [査読有り]

     概要を見る

    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) <-> 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年04月  [査読有り]

     概要を見る

    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

▼全件表示

Misc

  • 半透明Ta3N5薄膜光電極の水分解活性に対するカーボンナノチューブ基板修飾の効果

    赤木大二郎, 久富隆史, 佐々木豊, 小寺正徳, 橋爪裕太, 片山正士, 嶺岸耕, 野田優, 堂免一成

    触媒討論会討論会A予稿集   120th   517  2017年09月

    J-GLOBAL

  • SrTiO3:La,Rh及びTa3N5からなる光触媒シートの裏面導電層作製法の検討

    浅村竹彦, 王謙, 王謙, 久富隆史, 片山正士, 嶺岸耕, 野田優, 堂免一成

    触媒討論会討論会A予稿集   120th   90  2017年09月

    J-GLOBAL

  • カーボンナノチューブ基板を用いた水分解用Ta3N5薄膜光アノードの開発

    赤木大二郎, 久富隆史, 佐々木豊, 青井慈喜, 片山正士, 嶺岸耕, 野田優, 堂免一成

    日本化学会春季年会講演予稿集(CD-ROM)   97th   ROMBUNNO.3A8‐16  2017年03月

    J-GLOBAL

  • カーボンナノチューブスポンジ膜への硫黄包含によるリチウム硫黄電池正極の開発

    堀圭佑, 長谷川馨, 仁科勇太, 門間聰之, 逢坂哲彌, 野田優

    化学工学会年会研究発表講演要旨集(CD-ROM)   81st  2016年

    J-GLOBAL

  • Siナノ粒子をカーボンナノチューブ膜に包含したLi二次電池用負極の開発

    小輪瀬敬之, 長谷川馨, 門間聰之, 逢坂哲彌, 野田優

    化学工学会年会研究発表講演要旨集(CD-ROM)   81st  2016年

    J-GLOBAL

  • 銅薄膜の急速蒸着とリチウム二次電池電極応用

    青井慈喜, 長谷川馨, 大沢利男, 門間聰之, 逢坂哲彌, 野田優

    化学工学会年会研究発表講演要旨集(CD-ROM)   80th  2015年

    J-GLOBAL

  • リチウム二次電池に向けたシリコン粒子膜の集電体上直接形成

    森川裕介, 長谷川馨, 門間聰之, 逢坂哲彌, 野田優

    化学工学会年会研究発表講演要旨集(CD-ROM)   80th  2015年

    J-GLOBAL

  • ガス中蒸発法によるシリコンナノ粒子の作製とリチウム二次電池用三次元厚膜電極の開発

    小輪瀬敬之, 長谷川馨, 門間聰之, 逢坂哲彌, 野田優

    化学工学会年会研究発表講演要旨集(CD-ROM)   80th  2015年

    J-GLOBAL

  • カーボンナノチューブ膜への硫黄の包含によるリチウム硫黄電池正極の開発

    堀圭佑, 長谷川馨, 門間聰之, 逢坂哲彌, 野田優

    化学工学会年会研究発表講演要旨集(CD-ROM)   80th  2015年

    J-GLOBAL

  • Li二次電池負極を目指した柔軟性電極上への多孔質Si膜の急速蒸着と電気化学評価

    房楠, 長谷川馨, 門間聰之, 逢坂哲彌, 野田優

    化学工学会年会研究発表講演要旨集(CD-ROM)   79th  2014年

    J-GLOBAL

  • 電気化学キャパシタを目指したカーボンナノチューブ自立膜とMnO2粒子の複合電極の作製

    成林美里, 長谷川馨, 門間聰之, 逢坂哲彌, 野田優

    化学工学会年会研究発表講演要旨集(CD-ROM)   79th  2014年

    J-GLOBAL

  • 電気化学キャパシタを目指したカーボンナノチューブ自立膜とMnO2粒子複合電極の作製

    成林美里, 長谷川馨, 門間聰之, 逢坂哲彌, 野田優

    電気化学秋季大会講演要旨集   2014  2014年

    J-GLOBAL

  • Li二次電池負極を目指した柔軟性電極上への多孔質Si膜の急速蒸着と電気化学評価

    房楠, 長谷川馨, 門間聰之, 逢坂哲彌, 野田優

    化学工学会大会講演要旨集(CD-ROM)   2014  2014年

    J-GLOBAL

  • Combinatorial Control of Catalyst Nanoparticles for Customized Production of Single- and Multi-Walled Carbon Nanotubes

    NODA Suguru, HASEGAWA Kei, SUGIME Hisashi, KAKEHI Kazunori, MARUYAMA Shigeo, YAMAGUCHI Yukio

    Extended abstracts of the ... Conference on Solid State Devices and Materials   2007   1180 - 1181  2007年09月

    CiNii

  • C113 一酸化炭素からの単層カーボンナノチューブ合成に与えるCo/Mo比の影響(OS-11 ナノスケール伝熱I)

    西井 俊明, 村上 陽一, 野田 優, 杉目 恒志, 桝山 直人, 丸山 茂夫

    熱工学コンファレンス講演論文集   2005   97 - 98  2005年11月

     概要を見る

    Co and Mo are often used as catalysts for the catalytic chemical vapor deposition (CCVD) synthesis of single-walled carbon nanotubes (SWNTs) on a substrate. In this study, the influence of the Co/Mo ratio on the SWNT synthesis from carbon monoxide under atmospheric pressure was evaluated by the combinatorial method, using a library of sputter-doposited Co and Mo patterns.

    CiNii

  • CVD 合成膜の優先配向決定メカニズム

    梶川 裕矢, 野田 優, 小宮山 宏

    日本結晶成長学会誌   29 ( 2 ) 45 - 45  2002年07月

     概要を見る

    Preferred orientation (PO) of chemical vapor deposited polycrystalline films greatly affects film properties. Therefore controlling PO has provoked a great deal of controversy in many years [ 1,2] . We have found a relation between PO and flux of the growth species and explained it by the rate-determining step of adsorption or reaction by applying Langmuir-type adsorption model.

    CiNii

  • 材料プロセッシングにおける形体・構造制御のためのエキスパートシステムの開発

    野田優, 辻佳子, 大沢利男, 小宮山宏, 奥山喜久夫, 島田学, 江頭靖幸, 松方正彦, 野村幹弘, 舟窪浩 KimHeeJoon, 井原学, 高見誠一

    化学工学会第65回年会    2001年

  • 材料プロセッシングにおける形体・構造制御のためのソフトウエアツール開発

    野田優, 辻佳子, 大沢利男, 小宮山宏, 奥山喜久夫, 島田学, 江頭靖幸, 松方正彦, 野村幹弘, 舟窪浩 KimHeeJoon, 井原学, 高見誠一

    化学工学会第65回年会    2000年

  • 異常成長の知識の構造化と材料構造制御を目指したシステム開発

    野田優, 辻佳子, 劉学東, 大沢利男, 小宮山宏, 奥山喜久夫, 島田学, 江頭靖幸, 松方正彦, 野村幹弘, 舟窪浩, KimHeeJoon

    化学工学会第65回年会    2000年

▼全件表示

産業財産権

  • カーボンナノチューブの製造方法、並びにカーボンナノチューブを含む構造体及び複合体

    野田 優, 杉目 恒志, 楊 孟儒, 陳 鵬飛, 仲川 黎

    特許権

  • 窒化ホウ素ナノチューブの製造方法

    野田 優, 沢田 哲郎, 清 智弘, 高橋 宏夢

    特許権

  • 二次電池正極、二次電池正極の製造方法、二次電池の製造方法

    野田 優, 吉江 優一, 堀 圭佑

    特許権

  • 導電材、およびこれを利用した導電膜ならびに太陽電池

    野田 優, 謝 栄斌

    特許権

  • 蓄電デバイス用セパレータ及びその製造方法、蓄電デバイス用一体構造物及びその製造方法

    野田 優, 金子 健太郎, 堀 圭佑

    特許権

  • 柔軟導電膜及びその製造方法

    野田 優, 川上 慧, 小林 峻司

    特許権

  • カーボンナノチューブの製造装置および製造方法

    野田 優, 並木 克也, 張 子豪, 大沢 利男, 杉目 恒志

    特許権

  • カーボンナノチューブ、その製造方法および製造装置

    杉目 恒志, 佐藤 俊裕, 仲川 黎, 野田 優

    特許権

  • 立体型櫛型電極およびその製造方法

    杉目 恒志, 野田 優

    特許権

  • 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

    野田 優, 堀 圭佑, 前 智太郎, 橋爪 裕太

    特許権

  • 炭素-金属構造体および炭素-金属構造体の製造方法

    野田 優, 北川 紗映

    特許権

  • 触媒付着体の製造方法及び製造装置、並びに、繊維状炭素ナノ構造体の製造方法及び製造装置

    野田 優, 李 墨宸, 前田 里沙, 大沢 利男

    特許権

  • 触媒担持体及びその調製方法

    野田 優, 吉田 昌広, 大沢 利男

    特許権

  • カーボンナノチューブ製造用の触媒前駆組成物とその製造方法、および、触媒前駆組成物を用いたカーボンナノチューブの製造方法と製造装置

    6675647

    野田 優, 岡田 翔平

    特許権

  • 二次電池

    野田 優

    特許権

  • 自立した銅薄膜の製造方法

    野田 優, 青井 慈喜

    特許権

  • カーボンナノチューブの製造装置と製造方法

    野田 優, 大沢 利男, 中村 典義

    特許権

  • グラフェンの製造方法

    野田 優, 増田 竜也

    特許権

▼全件表示

受賞

  • 2020年度 大隈記念学術褒賞 奨励賞

    2020年11月   早稲田大学   「ナノ材料の実用合成プロセスの研究」  

    受賞者: 野田優

  • 次代の中核研究者

    2020年04月   早稲田大学  

    受賞者: 野田優

  • 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年08月   日本学術振興会  

    受賞者: 野田 優

  • 2016 EDS Paul Rappaport Award

    2017年12月   IEEE Electron Devices Society   "A color-tunable polychromatic organic-light-emitting-diode device with low resistive intermediate electrode for roll-to-roll manufacturing"  

    受賞者: T. Tsujimura, T. Hakii, S. Noda

  • 早稲田大学ティーチングアワード

    2016年04月   早稲田大学   「材料プロセス工学」  

    受賞者: 野田 優

  • 早稲田大学ティーチングアワード

    2014年04月   早稲田大学   「材料プロセス工学」  

    受賞者: 野田 優

  • Distinguished Lecture in Chemical Engineering, Hiroshima University

    2014年04月   Department of Chemical Engineering, Hiroshima University  

    受賞者: 野田 優

  • 平成17年度化学工学会奨励賞(玉置明善記念賞)

    2006年03月   化学工学会   「薄膜プロセスでの自己組織的構造形成の理解とナノ材料の合理的作製」  

    受賞者: 野田 優

▼全件表示

共同研究・競争的資金等の研究課題

  • 安全・高性能なナノチューブベース二次電池の開発と、温室効果ガス排出削減効果の評価

    日本学術振興会  科学研究費助成事業 基盤研究(A)

    研究期間:

    2021年04月
    -
    2024年03月
     

    野田 優

  • 窒化ホウ素ナノチューブの実用合成法の開発

    日本学術振興会  科学研究費助成事業 挑戦的研究(萌芽)

    研究期間:

    2021年07月
    -
    2023年03月
     

    野田 優

  • 水素の高効率製造に向けた金属カルコゲナイト触媒による水電解の機構研究

    日本学術振興会  科学研究費助成事業 特別研究員奨励費

    研究期間:

    2019年04月
    -
    2021年03月
     

    野田 優, SENGENI ANANTHARAJ

     概要を見る

    遷移金属の水酸化物およびカルコゲナイドを中心に、水電解触媒の最新の研究成果を調査しレビュー論文の執筆・発表を進めた。ニッケルは水素被毒のため水素発生活性が低いが、そのカルコゲナイドは酸およびアルカリの両方で高い水素発生活性を示す。その作用機構と触媒表面の化学変化の重要性を議論、硫化物・セレン化物・テルル化物の活性・選択性・安定性を比較し、今後の研究開発の方向性を示す総説を発表した。また、化学組成に加え結晶構造も水電解活性に大きな影響を持ち、特にアモルファスが結晶よりも高い活性を示す触媒が多数報告されている。多数の触媒材料の既往研究を調査、電解液の触媒内部へのアクセス容易性と電気化学活性表面積の高さ、構造の再構成の容易性と欠陥密度の高さなどその作用機構を議論、今後の研究開発の方向性を示す総説を発表した。
    これらの調査研究をもとにポイントを絞った実験研究も推進した。遷移金属カルコゲナイドは酸素発生反応にも多用されるが、その際はプレ触媒であり、実際には酸化された状態で作用する。CoSe2のアルカリ水電解での酸素発生反応を検討、CoSe2調整時に事前酸化することで活性を大きく向上できることを見出した。また、金属フォームは電極触媒の三次元化に有効であり、銅フォームおよびニッケルフォームの電気化学的処理による触媒形成と水電解の検討を進めている。加えて、カーボンナノチューブ(CNT)の柔軟で良導電性なスポンジ状自立膜を三次元電極とし、その表面にNi(OH)2を電着した触媒の開発も進めている。本Ni(OH)2-CNT複合体は電気化学キャパシタ向けに開発していたものであるが、アルカリ水電解におけるニッケル触媒の実際の化学状態はNi(OH)2であることに着目し転用した。微量のFe添加により酸素発生活性が大きく上がることが知られており、現在、電解槽でのin situ Fe添加の検討を進めている。

  • 簡易・高速プロセスによるソフト電池の創製と、構造変化の可逆化による容量革新

    日本学術振興会  科学研究費助成事業 基盤研究(S)

    研究期間:

    2016年05月
    -
    2021年03月
     

    野田 優, 門間 聰之, 山田 裕貴, 獨古 薫

     概要を見る

    野田は、従来材料の黒鉛とLCOを用いた全電池で多種類のCNTを比較検討した。複合膜の自立性と導電性の点で長く、副反応を抑える点で比表面積が大きすぎない数層CNTが適することを見出した。Si-CNT高容量負極では、負極/正極容量比を高く設定しLiを多く含む状態を保つと、Siの体積変化を抑えて安定動作できることを見出した。金属Liでは50 μmと薄いLi箔を用いてLi-Cu-CNTスポンジ負極を開発、セル基準での高容量密度を可能とした。S-CNT高容量正極は電解液量を削減すると動作しなくなる。多硫化リチウム-CNTスポンジ正極を開発、電解液量を削減しても高容量を示すことを確認、薄い金属Li負極と組み合わせた全電池にて電極質量基準で1000 Wh/kgの高エネルギー密度を実現した。門間は野田と共同で、充放電時のスポンジ電極の体積変化の測定を開始、測定系を改良中である。また、スポンジ電極として期待されるSi-O-C 電極およびSn-Ni負極の充放電時の体積変化を評価、論文報告した。獨古は、リチウム塩とジニトリル系溶媒からなる濃厚電解液でLi+がアニオンや溶媒よりも速く拡散するホッピング伝導機構を見出した。この電解液をリチウム硫黄電池へ適用、硫黄正極の反応中間体の溶出が抑制され、高いクーロン効率での充放電を実現した。高電流密度では充電時にLi金属負極上で電解液が徐々に還元分解することが課題である。山田は、前年度にSi系負極の高いサイクル可逆性を確認したフッ素化鎖状カーボネート溶媒を含む高濃度電解液に着目、その基礎物性及びSEI被膜の形態・組成を調査し、Si系電極上にsulfideを含む緻密な粒子状のSEI被膜が形成されることを明らかにした。また5 V級LiNi0.5Mn1.5O4正極の安定な充放電サイクルも確認、上記電解液が高い酸化安定性を有すことを見出した。

  • 大結晶シリコン薄膜-ナノチューブ・フレキシブル太陽電池の開発と簡易製造

    日本学術振興会  科学研究費助成事業 挑戦的萌芽研究

    研究期間:

    2015年04月
    -
    2017年03月
     

    野田 優

     概要を見る

    炭素と珪素という豊富な元素を用い、簡易・高速・高収率なプロセスで、軽量・安定・低コストなフレキシブル太陽電池の実現を目指した。バルクSi型に対して高純度Siを数十倍有効利用すべく、Si膜の高速製造法を開発した。Si源を融点1414 ℃より高温の2000 ℃に加熱して1 minに10 μmの高速製膜を実現、その際に成長基板を融点以上から融点以下へ下げることで100 μm以上の面内結晶粒径を実現した。簡易なセル化技術も開発した。市販のカーボンナノチューブ粉末を界面活性剤水溶液に分散し、吸引ろ過で薄膜を作製、n型Siウェハに貼り付け、変換効率10%のセルを実現した。今後、両技術の接続に取り組む。

  • 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

    日本学術振興会  科学研究費助成事業 基盤研究(A)

    研究期間:

    2013年10月
    -
    2017年03月
     

    野田 優

     概要を見る

    新規活物質による蓄電デバイスの革新に向け、簡易・高速・高収率プロセスにより三次元ナノ構造電極を開発した。Siは黒鉛の10倍の負極容量を持つ。数μm厚さのSiおよびSi-Cu多孔質負極のCu集電体上への1分での作製を、安価なバルク原料で急速蒸着法により実現した。純度99.6 wt%超のサブミリメータ長の数層カーボンナノチューブ(CNT)を流動層で半連続合成、このCNTは精製処理なしに各種用途に利用できる。CNTを活性炭、コバルト酸リチウムや黒鉛と共分散・ろ過して数10 μm厚さの自立膜を作製、金属細線での部分的コンタクトで電極動作した。キャパシタや二次電池での重い金属集電体の利用の最小化を図る。

  • 単層カーボンナノチューブの火炎合成への挑戦

    日本学術振興会  科学研究費助成事業 挑戦的萌芽研究

    研究期間:

    2013年04月
    -
    2015年03月
     

    野田 優

     概要を見る

    単層カーボンナノチューブ(単層CNT)は、直径1 nm前後の1次元ナノ材料で、多様な応用が期待されている。金属ナノ粒子を触媒に用いた化学気相成長(CVD)法が主流の合成法だが、数万円/gと非常に高価で実用化していない。本研究では、カーボンブラックやフラーレンの量産に実績がある火炎合成法により単層CNT合成に挑んだ。予混合火炎によりフェロセンを瞬時に熱分解して鉄蒸気を発生、硫黄を含むアルゴンガスと瞬時に混合して1000-1400 ℃に冷却してFe触媒粒子を核生成し、予熱したメタンガスと混合してCVDを行う独自設計により、単層CNTの合成を実現した。

  • 単層カーボンナノチューブ構造体の自己組織化成長

    日本学術振興会  科学研究費助成事業 若手研究(A)

    研究期間:

    2009年
    -
    2011年
     

    野田 優

     概要を見る

    単層カーボンナノチューブ(単層CNT)は、その特異な1次元ナノ構造と優れた各種物性から多様な応用が期待されるが、反面、合成/実装技術が未確立で実用例は僅かである。単層CNTは基板上に成長する過程で、互いに相互作用し多様な集合形態をとることが分かってきた。この自己組織化を基礎的に理解するとともに、応用で求められる単層CNT集合体をデバイス基板上に直接成長・実装させる技術基盤化を進めた。

  • コンビナトリアル手法による単層カーボンナノチューブ成長の系統的検討と全体像の構築

    日本学術振興会  科学研究費助成事業 若手研究(A)

    研究期間:

    2006年
    -
    2008年
     

    野田 優

     概要を見る

    カーボンナノチューブ(CNT)は多様な応用が期待される反面、合成技術が未確立で実用例は僅かである。本研究では1度に広範な触媒条件を探索できるコンビナトリアル手法を用い、化学蒸着法による単層CNT触媒成長を系統的に検討した。0.1-1nm厚の触媒層からの粒子形成と単層/多層CNT成長、Al_2O_x担体によるCNT成長加速、触媒粗大化とCNT直径増大・成長急停止、Mo助触媒による触媒粗大化抑制、前駆体アセチレンの気相生成等を解明、体系化した。

  • 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)

    研究期間:

    2003年
    -
    2005年
     

    野田 優

     概要を見る

    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。

  • グラフェン関連原子層の新規合成法および大面積合成法の開発

    日本学術振興会  科学研究費助成事業 新学術領域研究(研究領域提案型)

    研究期間:

    2013年06月
    -
    2018年03月
     

    楠 美智子, 斉木 幸一朗, 野田 優, 丸山 茂夫, 北浦 良, 依光 英樹, 篠原 久典, 大野 雄高

     概要を見る

    合成班内での徹底討論を通し、(1)化学気相蒸着法により、大面積化とともに高品質化(結晶サイズ5mm以上)、実用に向けた高速合成化を実現。h-BNを基板上、シャープな発光ピークを示す単層WS2を直接成長。(2)SiC熱分解法による大面積グラフェン合成実現と、急冷法開発による基板からの自立化に成功。(3)h-BN膜上酸化グラフェンのメタンプラズマ照射による高移動度(4000-7000cm2/Vs)実現。(4)パラジウム触媒を用いた有機化学合成法により斬新なグラフェンリボン合成に続々成功し、近赤外光吸収の増強解明。国内・海外への活発なサンプル提供を行い、共同研究による論文成果130件。

  • 単層カーボンナノチューブのカイラリティ制御CVD合成と分離技術開発

    日本学術振興会  科学研究費助成事業 特定領域研究

    研究期間:

    2007年
    -
    2011年
     

    丸山 茂夫, 佐野 正人, 大久保 達也, 野田 優, 塩見 淳一郎, 千足 昇平

     概要を見る

    単層カーボンナノチューブの応用展開には不可欠である高度な構造制御(カイラリティ)制御を目指し,カイラリティ制御合成法および合成後の分離技術開発を行った.分光法や電気伝導特性計測によってカイラリティ分析を行った.合成においては,コンビナトリアル法やSAM膜による触媒制御,およびCVDガス制御の効果を明らかにし,水晶基板上での配向成長の機構を解明した.また,合成後の分離精製としてDGU法を用い,電気伝導性や特定のカイラリティの単離技術の開発に成功した.

  • 原料リサイクルCVD法による太陽電池用結晶シリコン薄膜の低コスト合成

    日本学術振興会  科学研究費助成事業 基盤研究(A)

    研究期間:

    2003年
    -
    2005年
     

    岡田 文雄, 小宮山 宏, 野田 優, 岡田 文雄

     概要を見る

    大規模太陽光発電はクリーンエネルギーシステム構築に不可欠である。バルクシリコン型は、資源量・安定性・安全性・発電効率等に優れ、現状8-9割を占める。しかしシリコン供給が半導体産業に依存し、生産量拡大の限界が指摘されている。本研究では、シリコン基板の大規模・低コスト製造法を研究した。
    現状、シリコン基板はインゴットのスライスで作られ、基板厚さ換算500μm程度のシリコンを消費している。厚さ10μm程度の薄膜に置きかえれば、大規模化・低コスト化が同時に果たせる。そこで、単結晶シリコン基板を鋳型とし、犠牲層を介して発電層シリコンをヘテロエピタキシャル成長、犠牲層を溶解し、単結晶シリコン薄膜を得、基板を繰り返し利用するエピタキシャルリフトオフ(ELO)法を研究した。
    この際、発電層シリコンのエピタキシャル成長が重要となる。化学蒸着(CVD)法が一般に用いられるが、原料のクロロシランの利用率が低い。クロロシランは金属級シリコンと塩化水素の反応で合成する為、そこにCVD出口ガスをリサイクルすることで、金属級シリコンが入り単結晶シリコン薄膜が出る、無駄のないプロセスができる。現行のクロロシラン製造プロセスの調査に加え、クロロシラン生成とCVDの反応速度過程の実験的検討も行い、リサイクルプロセスの妥当性を検証した。しかし、塩素を用いることによる不純物の混入や、シリコンエピタキシャル成長中の犠牲層の構造劣化の問題が判明した。一方で、一般には低温で低速にエピタキシーさせる物理蒸着(PVD)法が本プロセスに有効なことが示唆された。急速蒸着(RVD)法のコンセプトの下、基板温度800-1000℃にて10μm/minのエピタキシャル成長を確認した。
    ELO法と、RVD法を組み合わせ、小面積ながら厚さ5-10μmの単結晶シリコン薄膜のリフトオフに成功、これはシリコン問題の解決に繋がる重要な成果である。

▼全件表示

学内研究費(特定課題)

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

     概要を見る

    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年  

     概要を見る

    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 µm/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 µm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。

 

現在担当している科目

▼全件表示