We present a novel optical device for the analysis of chemical surface properties utilizing surface-enhanced Raman scattering. The device, a transmission-type plasmonic sensor (TPS), offers the advantages of high sensitivity, nondestructive sample characterization, simple setup, and low-cost fabrication. The TPS is composed of Ag nanoparticles (NPs) deposited on a convex quartz glass substrate. The enhanced Raman spectrum is acquired by focusing a laser beam perpendicular to the sample surface through the substrate. The laser beam generates plasmon polarization in droplet-shaped Ag NPs at the sensor/sample interface. Our results indicate the potential of the device as a versatile surface-analytical tool. (C) 2016 The Japan Society of Applied Physics

The internal structure of self -assembled monolayers (SAMs) such as 3-aminopropyltriethoxysilane (APTES) fabricated on a glass substrate is difficult to characterize and analyze at nanometer level. In this study, we employed surface -enhanced Raman spectroscopy (SERS) to study the internal molecular structure of APTES SAMs. The sample APTES SAMs were deposited with Ag nanoparticles to enhance the Raman signal and to obtain subtler structure information, which were supported by density functional theory calculations. In addition, in order to carry out high -resolution analysis, especially for vertical direction, a fine piezo electric positioner was used to control the depth scanning with a step of 0.1 nm. We measured and distinguished the vertical Raman intensity variations of specific groups in APTES, such as Ag/NH2, CH2, and Si-O, with high resolution. The interfacial bond at the two interfaces of Ag-APTES and APTES-SiO2 was identified. Moreover, APTES molecule orientation was demonstrated to be inhomogeneous from frequency shift. (C) 2017 Elsevier B.V. All rights reserved.

The morphological evolution of zinc during electrodeposition from an alkaline zincate solution, i.e., corresponding to charging operation in secondary zinc batteries, was investigated. The initiation and propagation of mossy structures were particularly focused; mossy structures represent one of the undesired, irregular morphologies at low cathodic overpotential. Scanning electron microscopy observations showed that mossy structures formed transiently from layer-like morphology followed by the formation of protrusions with a size of submicrometers. These protrusions still exhibited layer-like features in the initial stage. In addition to this transition behavior, the propagation of mossy structures was monitored in situ by optical microscopy. At -5.0 mA cm(-2), mossy structures formed successively and propagated, while there was no clear change in layer-like morphology during deposition outside these characteristic structures. At -20 mA cm(-2), the layer-like growth proceeded for longer duration and the population of the mossy structures apparently decreased. However, they continuously increased in size followed by successive formation of mossy structures once initiated. From these results, growth mode of zinc at low cathodic overpotential transiently changed from layer-like growth to mossy structure evolution accompanied with dynamic variations in local current density. (c) 2016 Elsevier Ltd. All rights reserved.

The morphological evolution of zinc during electrodeposition from an alkaline zincate solution, i.e., corresponding to charging operation in secondary zinc batteries, was investigated. The initiation and propagation of mossy structures were particularly focused; mossy structures represent one of the undesired, irregular morphologies at low cathodic overpotential. Scanning electron microscopy observations showed that mossy structures formed transiently from layer-like morphology followed by the formation of protrusions with a size of submicrometers. These protrusions still exhibited layer-like features in the initial stage. In addition to this transition behavior, the propagation of mossy structures was monitored in situ by optical microscopy. At -5.0 mA cm(-2), mossy structures formed successively and propagated, while there was no clear change in layer-like morphology during deposition outside these characteristic structures. At -20 mA cm(-2), the layer-like growth proceeded for longer duration and the population of the mossy structures apparently decreased. However, they continuously increased in size followed by successive formation of mossy structures once initiated. From these results, growth mode of zinc at low cathodic overpotential transiently changed from layer-like growth to mossy structure evolution accompanied with dynamic variations in local current density. (c) 2016 Elsevier Ltd. All rights reserved.

We report the fabrication and evaluation of the Cu/Bi bilayer absorber with electrodeposition. We designed the Cu/Bi absorber to satisfy the requirements for scanning transmission electron microscope (STEM). The residual resistivity ratios of films of Cu and Bi with electrodeposition was and , respectively; these values are sufficient for the requirements of STEM. We found that the Cu/Bi bilayer absorber TES microcalorimeter experienced a pulse-shape variation and we considered that these variations were caused by the quality of the contact surface between the absorber and TES. In addition, we examined the structure of the absorber using focus ion beam analysis and STEM. The results suggest that an oxidation between the Cu and seed layer, in which the layer is an electrode for electrodeposition, yielded variations. Moreover, thermal simulation suggests that the thermal conduction between the absorber and TES caused variations. The results of this study will improve the process of Bi electrodeposition.

We present a novel optical device for the analysis of chemical surface properties utilizing surface-enhanced Raman scattering. The device, a transmission-type plasmonic sensor (TPS), offers the advantages of high sensitivity, nondestructive sample characterization, simple setup, and low-cost fabrication. The TPS is composed of Ag nanoparticles (NPs) deposited on a convex quartz glass substrate. The enhanced Raman spectrum is acquired by focusing a laser beam perpendicular to the sample surface through the substrate. The laser beam generates plasmon polarization in droplet-shaped Ag NPs at the sensor/sample interface. Our results indicate the potential of the device as a versatile surface-analytical tool.

Effects of Pb and Sn additives on electrodeposition of Zn were investigated for the applications in Zn secondary battery, focused on their roles on morphological evolution. Similarly to well-known effect of Pb addition to smoothly electrodeposit Zn film surface, Sn also exhibited to suppress the formation of mossy structures, which were highly filamentous Zn electrodeposits to cause frequently battery failure. Pb significantly shifted deposition potential of Zn to negative value at concentration less than 1.0 mmol dm(-3), while Sn showed no substantial effect even at 50 mmol dm(-3). The morphological evolution analysis demonstrated that the addition of 1.0 mmol dm(-3) Pb significantly altered nucleation behavior of Zn at initial stages of deposition; stacking of layer-like structures (microsteps) were altered to discrete and uniform nuclei of Zn preferentially oriented to (002) direction. In contrast, with Sn additive, morphological features at the initial stage of deposition were similar to that without additive. However, microsteps evolution was gradually suppressed and relatively strong (002) texture of electrodeposited Zn was mitigated by Sn addition. These results suggested that the beneficial roles of Pb and Sn addition on Zn morphological evolution were ascribed to different reasons; Pb diminished the active growth sites of Zn surface by suppressing the deposition reaction of Zn, while Sn suppressed microsteps evolution by different texture evolution of Zn. (C) 2017 Elsevier Ltd. All rights reserved.

A structure's temperature can be determined from the Raman spectrum using the frequency and the ratio of the intensities of the anti-Stokes and Stokes signals (the I-as/I-s ratio). In this study, we apply this approach and an equation relating the temperature, Raman frequency, and I-as/I-s ratio to in-situ estimation of the phase change point of a (3-aminopropyl)triethoxysilane self-assembled monolayer (APTES SAM). Ag nanoparticles were deposited on APTES to enhance the Raman signals. A time-resolved measurement mode was used to monitor the variation in the Raman spectra in situ. Moreover, the structural change in APTES SAM (from ordered to disordered structure) under heating was discussed in detail, and the phase change point (around 118 degrees C) was calculated. (C) 2015 Elsevier B.V. All rights reserved.

We have fabricated Co-Pt nanodot arrays by combining electrodeposition with electron beam lithography (EBL) for applications in ultra-high density magnetic recording media, such as bit-patterned media (BPM). In this work, we analyzed the initial nucleation and growth of Co-Pt inside nanopores to achieve nanodot arrays with high deposition uniformity, as well as magnetic properties. At -900 mV (vs. Ag/AgCl), multiple nuclei of 2.0-3.0 nm in size were randomly distributed, even in nanopores with a 10 nm diameter, which could result in a lack of uniformity in the magnetic properties. The number of nuclei was then reduced by applying a less negative potential (>-700 mV vs. Ag/AgCl) to deposit a single nucleus inside each nanopore. As a result, a single grain of 5.0-10 nm in size was successfully deposited inside the nanopore, which could induce uniform magnetic properties in each nanodot. In addition, at less negative potentials, the coercivity of the Co-Pt films increased, which was induced by the epitaxial-like growth of Co-Pt from the Ru substrate. Cross-sectional TEM analysis suggested that Co-Pt deposited with a less negative potential was single crystalline with uniform hcp lattice fringes in the direction perpendicular to the Ru interface, indicating the formation of highly uniform nanodot arrays with high perpendicular magnetic anisotropy. (C) 2015 Elsevier Ltd. All rights reserved.

As one of the most cost-effective methods to produce solar-grade silicon (SOG-Si), purification of silica solution by extracting its impurities through wet chemical processes has been proposed. This paper reports on the design of channel type reactor for liquid-liquid extraction to purify silica solution, focusing particularly on the extraction of B (boric acid) in aqueous phase with 2,2,4-trimethyl-1,3-pentanediol (TMPD) in organic phase. The reactor fabricated by 3D printing technology was designed to have two characteristic structures: (i) a throat structure that shows gradually diverging part after converging near Y shaped inlets and (ii) obstacles structure on downstream. Two solutions were made to contact with each other by turbulent mixing around the throat structure, causing small droplets formation that was dispersed and retained efficiently even on downstream by obstacles structure. This droplet dispersion shortens diffusion distance of boric acid to meet TMPD at the liquid-liquid interface, providing efficient mass transfer. At higher flow rate i.e., 380 ml/min, the extraction efficiency was 97.43% after the multi stage process. The results suggest that the channel type reactor designed here is profitable for elimination of impurities, such as B or P, in silica solution to produce SOG-Si.

The thickness of 3-dimensional (3D) mesoporous silica ultrathin films was controlled at a single-nano-meter scale by wet-etching. A drop casting method with an aqueous etchant of ammonium fluoride was effective in etching the surfaces of films in the direction perpendicular to their substrates. The decrease in the film thickness depends on the interface tension of etching solutions. The wettability of thin films also influences the etching. CoPt nanodots were electrodeposited within ultrathin silica films on Ru substrates to form CoPt nanodot patterns.

FeCuPt nanodot arrays were fabricated by electrodeposition onto a nanopore patterned substrate fabricated by electron beam lithography (EBL), for the purpose to manufacture and characterize model bit-patterned media. Addition of Cu to FePt was carried out to accelerate the phase transformation of FePt into the L10 -ordered phase in order to fabricate nanodot arrays with hard and uniform magnetic properties. Composition of the FeCuPt ternary alloy films was optimized by varying applied potential and CuSO4 concentration to form single L10 phase (40-50 at% Pt and 25 at% Cu). Annealing at 450 °C resulted in the phase transformation from fcc to L10 in FeCuPt ternary alloy films, whereas FePt binary alloy films did not show a phase transformation. Perpendicular coercivities of FeCuPt and FePt were 6 and 1 kOe, respectively, annealing at 450 °C, indicating the formation of the L10 phase with lower annealing temperature by Cu incorporation. FeCuPt nanodot arrays with 20 nm in diameter and 35 nm in pitch were successfully fabricated with the nanopore patterned substrate fabricated by EBL. In addition, cross-sectional transmission electron microscope analysis of FeCuPt nanodot arrays showed clear stacking of the L10 (111) lattice in a perpendicular direction through the growth direction having a single crystal nature, whereas phase transformation was insufficient with FePt nanodot arrays. The collective results have successfully demonstrated the electrochemical fabrication of ultra-fine FePt nanodot arrays with L10 structure by promoting L10 ordering with Cu additions.

Current interrupt and galvanostatic EIS techniques were utilized in a complementary fashion to characterize the different sources of overpotential during anodic gas evolution. Room temperature anodic evolution of oxygen at a nickel working electrode in aqueous potassium hydroxide and the high temperature (348°C) anodic evolution of chlorine at a glassy carbon working electrode in molten (LiCl) -(KCl)13.3-(CsCl) where investigatd. Combining of the two techniques enables to separate the total measured overpotential into its ohmic, charge transfer, and mass transfer components. Potential decay curves indicated that natural convection (due to both bubble evolution and density driven flow) was a major driving force in reestablishing equilibrium conditions at the working electrode surface. During oxygen evolution, charge transfer resistance dominated the total overpotential at low current densities, but as the current density approached ∼100mA/cm , mass transfer overpotentials and ohmic overpotential became non-negligible. The mass transfer overpotential during chlorine evolution was found to be half that found during oxygen evolution. 57.5 29.2 2

We report the fabrication and evaluation of the Cu/Bi bilayer absorber with electrodeposition. We designed the Cu/Bi absorber to satisfy the requirements for scanning transmission electron microscope (STEM). The residual resistivity ratios of films of Cu and Bi with electrodeposition was and , respectively; these values are sufficient for the requirements of STEM. We found that the Cu/Bi bilayer absorber TES microcalorimeter experienced a pulse-shape variation and we considered that these variations were caused by the quality of the contact surface between the absorber and TES. In addition, we examined the structure of the absorber using focus ion beam analysis and STEM. The results suggest that an oxidation between the Cu and seed layer, in which the layer is an electrode for electrodeposition, yielded variations. Moreover, thermal simulation suggests that the thermal conduction between the absorber and TES caused variations. The results of this study will improve the process of Bi electrodeposition.

The thermal stability of graphene has a close relationship with defect generation, thermal oxidation, which in turn have a significant bearing on its properties and applications. This report discusses the effect of confocal laser heating on the structure of single-layer graphene (SLG) on the basal plane and the edge. The thermal stability of SLG basal plane and edge was demonstrated to be different by using in situ anti-Stokes and Stokes Raman spectroscopy. The basal plane was found to be unstable above 500 degrees C, while the edge could not endure even 220 degrees C. The variation in the intensity of D, G, and 2D peaks and the intensity ratios of I(D)/I(G) and I(2D)/I(G) indicated that the thermal instability started with defect generation at the basal plane. The initial point defects at edge were partially eliminated at low temperature and generated again at temperatures above 220 degrees C. (C) The Electrochemical Society of Japan, All rights reserved.

A new electrolytic production process for solar-grade Si has been proposed utilizing liquid Si-Zn alloy cathode in molten CaCl2. To establish this process, the behavior of liquid Zn metal in molten CaCl2 at 1123 K was investigated. Evaporation of Zn metal was largely suppressed by immersion in the molten salt, which enabled the use of a Zn electrode despite its high vapor pressure. Cyclic voltammetry results suggested that the reduction of SiO2 on a Zn cathode proceeded at a more negative than 1.45 V vs. Ca2+/Ca. After potentiostatic electrolysis at 0.9 V, Si particles with sizes of 2-30 mu m were precipitated in the solidified Zn matrix by a slow cooling process. The rate-determining step for electrochemical reduction of SiO2 on the Zn cathode was discussed on the basis of a measurement of the alloying rate between solid Si and liquid Zn. (C) The Author(s) 2017. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse of the work in any medium, provided the original work is properly cited. All rights reserved.

CoPt nanodot arrays were fabricated by combining electrodeposition and electron beam lithography (EBL) for the use of bit-patterned media (BPM). To achieve precise control of deposition uniformity and coercivity of the CoPt nanodot arrays, their crystal structure and magnetic properties were controlled by controlling the diffusion state of metal ions from the initial deposition stage with the application of bath agitation. Following bath agitation, the composition gradient of the CoPt alloy with thickness was mitigated to have a near-ideal alloy composition of Co:Pt =80:20, which induces epitaxial-like growth from Ru substrate, thus resulting in the improvement of the crystal orientation of the hcp (002) structure from its initial deposition stages. Furthermore, the cross-sectional transmission electron microscope (TEM) analysis of the nanodots deposited with bath agitation showed CoPt growth along its c-axis oriented in the perpendicular direction, having uniform lattice fringes on the hcp (002) plane from the Ru underlayer interface, which is a significant factor to induce perpendicular magnetic anisotropy. Magnetic characterization of the CoPt nanodot arrays showed increase in the perpendicular coercivity and squareness of the hysteresis loops from 2.0 kOe and 0.64 (without agitation) to 4.0 kOe and 0.87 with bath agitation. Based on the detailed characterization of nanodot arrays, the precise crystal structure control of the nanodot arrays with ultra-high recording density by electrochemical process was successfully demonstrated.

In this work, the behavior of an additive designed to aid electrodeposition in through-silicon via (TSV) structures is monitored directly using surface enhanced Raman spectroscopy (SERS). A horizontal via structure with a transparent ceiling (corresponding to the side wall of the TSV) was prepared, which allowed the probe laser to reach the bottom of the structure (corresponding to the opposite side of the TSV wall). Au nanoparticles of size ~5 nm deposited on the bottom of the structure produced a SERS effect and enhanced the Raman signals of chemical species migrating nearby. The diffusion behavior of the additive inside the via structure could be monitored with high sensitivity by detecting these enhanced signals. As a case study, this direct measurement method was successfully used to follow the diffusion of a small amount of Janus Green B, a common additive for Cu electrodeposition. The diffusion coefficient of the additive determined by these measurements turned out to be different to that estimated electrochemically on flat electrodes. One of the advantages of our direct measurement setup is the ability to exclude the undesirable environmental changes that often occur in electrochemical measurements.

We have fabricated Co-Pt nanodot arrays by combining electrodeposition with electron beam lithography (EBL) for applications in ultra-high density magnetic recording media, such as bit-patterned media (BPM). In this work, we analyzed the initial nucleation and growth of Co-Pt inside nanopores to achieve nanodot arrays with high deposition uniformity, as well as magnetic properties. At -900 mV (vs. Ag/AgCl), multiple nuclei of 2.0-3.0 nm in size were randomly distributed, even in nanopores with a 10 nm diameter, which could result in a lack of uniformity in the magnetic properties. The number of nuclei was then reduced by applying a less negative potential (>-700 mV vs. Ag/AgCl) to deposit a single nucleus inside each nanopore. As a result, a single grain of 5.0-10 nm in size was successfully deposited inside the nanopore, which could induce uniform magnetic properties in each nanodot. In addition, at less negative potentials, the coercivity of the Co-Pt films increased, which was induced by the epitaxial-like growth of Co-Pt from the Ru substrate. Cross-sectional TEM analysis suggested that Co-Pt deposited with a less negative potential was single crystalline with uniform hcp lattice fringes in the direction perpendicular to the Ru interface, indicating the formation of highly uniform nanodot arrays with high perpendicular magnetic anisotropy. (C) 2015 Elsevier Ltd. All rights reserved.

As a fundamental study to develop a new process for producing solar-grade silicon, the effect of granule size on the kinetics of the electrochemical reduction of SiO2 granules in molten CaCl2 was investigated. SiO2 granules with different size ranges were electrolyzed in molten CaCl2 at 1123 K (850 A degrees C). The reduction kinetics was evaluated on the basis of the growth rate of the reduced Si layer and the behavior of the current during electrolysis. The results indicated that finer SiO2 granules are more favorable for a high reduction rate because the contact resistance between the bottom Si plate and the reduced Si particles is small and the diffusion of O2- ions in CaCl2 inside the porous Si shell is easy. Electrolysis using SiO2 granules less than 0.1 mm in size maintained a current density of no less than 0.4 A cm(-2) within 20 minutes, indicating that the electrochemical reduction of fine SiO2 granules in molten CaCl2 has the potential of becoming a high-yield production process for solar-grade silicon.

Total reflection X-ray fluorescence (TXRF) analysis is extensively used by the semiconductor industry for measuring trace metal contamination on silicon surfaces. In addition to determining the quantity of impurities on a surface, TXRF can reveal information about the vertical distribution of contaminants by measuring the fluorescence signal as a function of the angle of incidence. In this study, two samples were intentionally contaminated with copper in non-deoxygenated and deoxygenated ultrapure water (UPW) resulting in impurity profiles that were either atomically dispersed in a thin film or particle-like, respectively. The concentration profile of the samples immersed into deoxygenated UPW was calculated using a theoretical concentration profile representative of particles, yielding a mean particle height of 16.1 nm. However, the resulting theoretical profile suggested that a distribution of particle heights exists on the surface. The fit of the angular distribution data was further refined by minimizing the residual error of a least-squares fit employing a model with a Gaussian distribution of particle heights about the mean height. The presence of a height distribution was also confirmed with atomic force microscopy measurements.

CoPt nanodot arrays were fabricated by combining electrodeposition and electron beam lithography (EBL) for the use of bit-patterned media (BPM). To achieve precise control of deposition uniformity and coercivity of the CoPt nanodot arrays, their crystal structure and magnetic properties were controlled by controlling the diffusion state of metal ions from the initial deposition stage with the application of bath agitation. Following bath agitation, the composition gradient of the CoPt alloy with thickness was mitigated to have a near-ideal alloy composition of Co:Pt =80:20, which induces epitaxial-like growth from Ru substrate, thus resulting in the improvement of the crystal orientation of the hcp (002) structure from its initial deposition stages. Furthermore, the cross-sectional transmission electron microscope (TEM) analysis of the nanodots deposited with bath agitation showed CoPt growth along its c-axis oriented in the perpendicular direction, having uniform lattice fringes on the hcp (002) plane from the Ru underlayer interface, which is a significant factor to induce perpendicular magnetic anisotropy. Magnetic characterization of the CoPt nanodot arrays showed increase in the perpendicular coercivity and squareness of the hysteresis loops from 2.0 kOe and 0.64 (without agitation) to 4.0 kOe and 0.87 with bath agitation. Based on the detailed characterization of nanodot arrays, the precise crystal structure control of the nanodot arrays with ultra-high recording density by electrochemical process was successfully demonstrated.

Elementary steps in the electrochemical reduction process of SiCl4 in trimethyl-n-hexylammonium bis(trifluoromethylsulfonyl) imide (TMHATFSI) was investigated, focusing on molecular level behavior of the reactants at solid-liquid interface. Electrochemical measurements using an electrochemical quartz crystal microbalance (EQCM) identified a reduction peak corresponding to Si electrodeposition and several elementary steps with stable intermediates forming prior to the deposition. For detailed analysis, X-ray reflectivity (XRR) measurements with synchrotron radiation were applied in situ. The change in reflectivity of the electrode surface during the deposition was found to be due to the formation of a polymer-like Si such as Si2Cl6, which is an intermediate layer during the deposition process. These results were theoretically supported by density functional theory (DFT) calculations: after an electron transfers from the electrode, the Si in SiCl4 forms the bond with another SiCl4, rather than the Si of the substrate, resulting in the formation of the intermediate structure. These data suggest an elementary step in the SiCl4 reduction process which can be described as follows
when SiCl4 is reduced, a polymer-like Si form such as Si2Cl6 is generated. This intermediate species further reacts with other Si reactants after receiving additional electrons, which then finally deposits as Si on the substrate.

The internal structure of self -assembled monolayers (SAMs) such as 3-aminopropyltriethoxysilane (APTES) fabricated on a glass substrate is difficult to characterize and analyze at nanometer level. In this study, we employed surface -enhanced Raman spectroscopy (SERS) to study the internal molecular structure of APTES SAMs. The sample APTES SAMs were deposited with Ag nanoparticles to enhance the Raman signal and to obtain subtler structure information, which were supported by density functional theory calculations. In addition, in order to carry out high -resolution analysis, especially for vertical direction, a fine piezo electric positioner was used to control the depth scanning with a step of 0.1 nm. We measured and distinguished the vertical Raman intensity variations of specific groups in APTES, such as Ag/NH2, CH2, and Si-O, with high resolution. The interfacial bond at the two interfaces of Ag-APTES and APTES-SiO2 was identified. Moreover, APTES molecule orientation was demonstrated to be inhomogeneous from frequency shift. (C) 2017 Elsevier B.V. All rights reserved.

The thermal stability of graphene has a close relationship with defect generation, thermal oxidation, which in turn have a significant bearing on its properties and applications. This report discusses the effect of confocal laser heating on the structure of single-layer graphene (SLG) on the basal plane and the edge. The thermal stability of SLG basal plane and edge was demonstrated to be different by using in situ anti-Stokes and Stokes Raman spectroscopy. The basal plane was found to be unstable above 500 degrees C, while the edge could not endure even 220 degrees C. The variation in the intensity of D, G, and 2D peaks and the intensity ratios of I(D)/I(G) and I(2D)/I(G) indicated that the thermal instability started with defect generation at the basal plane. The initial point defects at edge were partially eliminated at low temperature and generated again at temperatures above 220 degrees C. (C) The Electrochemical Society of Japan, All rights reserved.

The hydrogen evolution reaction (HER) was investigated using Ni catalytic electrodes with micro-patterned surfaces. The present aim was to correlate HER efficiency with the surface wettability of Ni cathodes produced with different micropatterns. Regular Ni microdot arrays, 5–10 μm in diameter, 5–10 μm in pitch were fabricated on a 7 mm diameter Cu substrate and tested in alkaline water electrolysis (AWE) experiments. Using electrodes of this design, it may be possible to relate the electrochemical reaction kinetics to the electrolyte wettability localized to the microdot surface area. The surface microstructures of the electrode considerably influenced the reaction efficiency of the HER during alkaline water electrolysis at −20 mA cm . Furthermore, in situ video observations of the electrode surface during the HER revealed that the bubble size increased when the surface wettability of the electrodes was decreased. That is, the surface texture (micro-patterns) affected the HER efficiency by influencing bubble evolution and aggregation behavior. This observation may aid in the design of highly efficient HER catalytic electrodes. −2

The thermal stability of graphene has a close relationship with defect generation, thermal oxidation, which in turn have a significant bearing on its properties and applications. This report discusses the effect of confocal laser heating on the structure of single-layer graphene (SLG) on the basal plane and the edge. The thermal stability of SLG basal plane and edge was demonstrated to be different by using in situ anti-Stokes and Stokes Raman spectroscopy. The basal plane was found to be unstable above 500 degrees C, while the edge could not endure even 220 degrees C. The variation in the intensity of D, G, and 2D peaks and the intensity ratios of I(D)/I(G) and I(2D)/I(G) indicated that the thermal instability started with defect generation at the basal plane. The initial point defects at edge were partially eliminated at low temperature and generated again at temperatures above 220 degrees C. (C) The Electrochemical Society of Japan, All rights reserved.

Effects of Pb and Sn additives on electrodeposition of Zn were investigated for the applications in Zn secondary battery, focused on their roles on morphological evolution. Similarly to well-known effect of Pb addition to smoothly electrodeposit Zn film surface, Sn also exhibited to suppress the formation of mossy structures, which were highly filamentous Zn electrodeposits to cause frequently battery failure. Pb significantly shifted deposition potential of Zn to negative value at concentration less than 1.0 mmol dm(-3), while Sn showed no substantial effect even at 50 mmol dm(-3). The morphological evolution analysis demonstrated that the addition of 1.0 mmol dm(-3) Pb significantly altered nucleation behavior of Zn at initial stages of deposition; stacking of layer-like structures (microsteps) were altered to discrete and uniform nuclei of Zn preferentially oriented to (002) direction. In contrast, with Sn additive, morphological features at the initial stage of deposition were similar to that without additive. However, microsteps evolution was gradually suppressed and relatively strong (002) texture of electrodeposited Zn was mitigated by Sn addition. These results suggested that the beneficial roles of Pb and Sn addition on Zn morphological evolution were ascribed to different reasons; Pb diminished the active growth sites of Zn surface by suppressing the deposition reaction of Zn, while Sn suppressed microsteps evolution by different texture evolution of Zn. (C) 2017 Elsevier Ltd. All rights reserved.

To establish a new Si-electrodeposition process, the optimum conditions for obtaining adherent, compact, and smooth Si films using molten KF-KCl-K2SiF6 were investigated at 923 K. Galvanostatic electrolysis was conducted on a Ag substrate in eutectic KF-KCl (45:55 mol%) with various current densities (10-500 mA cm(-2)) and K2SiF6 concentrations (0.5-5.0 mol%). Cross-sectional scanning electron microscopy (SEM) of the deposits revealed that compact and smooth Si films form at intermediate K2SiF6 concentrations and current densities. The relationship between the deposition conditions and Si morphology is discussed in terms of the electrodeposition mechanism. (C) 2015 The Electrochemical Society. All rights reserved.

Theoretical analyses of L-alanine (L-Ala)- and L-homocysteine (L-Hcy)-Cu(II) complexes in basic, neutral, and acidic solutions were carried out using density functional theory to investigate the pH dependence of the formation mechanism of amino acid-Cu(II) complexes. The calculated complex formation energies indicate that the amino acid-Cu(II) complexes were expected to form in basic and neutral solutions but not in acidic solutions. The factors that determine the stability of these complexes are the coordination ability of each amino acid and the significance of intramolecular interactions among ligands within the complexes. As predicted from the molecular structure, in neutral solutions, the coordination ability of amino acid becomes lower than that in basic solutions because of the inert structure of the protonated amino group, -NH3+; however, the coordination ability originating from the -COO- group is estimated to be sufficient for stabilizing the entire complex system. Moreover, two H2O molecules coordinate with the central Cu2+ ion from the equatorial direction and interact with the coordinating amino acids, providing additional stability within the complex. In contrast, in acidic solutions, the complex does not have either sufficient coordination ability of amino acids or effective intramolecular interactions within the complex.

In this study, we construct composite structures of CoPt multilayer alloy nanowires by electrodeposition using a polycarbonate template membrane (PT). The holes in PT are subsequently filled with CoPt multilayer alloy films to form nanowires. The composition of the films can be controlled by modifying the potential to produce high anisotropy CoPt alloy multilayer nanowires. The CoPt multilayer nanowires have a periodic structure like bamboo with a chemical composition of (Co80Pt20/Co30Pt70)n. Polycrystalline and ferromagnetic characteristics were visible in a single layer of Co80Pt20 nanowire. A vertical 3D magnetic domain wall memory has a ferromagnetic bit layer and a domain wall layer. Thus (Co80Pt20/Co30Pt70)n multilayer nanowires can be used in domain wall controlled 3D memory devices like racetrack memory.

The thickness of 3-dimensional (3D) mesoporous silica ultrathin films was controlled at a single-nano-meter scale by wet-etching. A drop casting method with an aqueous etchant of ammonium fluoride was effective in etching the surfaces of films in the direction perpendicular to their substrates. The decrease in the film thickness depends on the interface tension of etching solutions. The wettability of thin films also influences the etching. CoPt nanodots were electrodeposited within ultrathin silica films on Ru substrates to form CoPt nanodot patterns.

Total reflection X-ray fluorescence (TXRF) analysis is extensively used by the semiconductor industry for measuring trace metal contamination on silicon surfaces. In addition to determining the quantity of impurities on a surface, TXRF can reveal information about the vertical distribution of contaminants by measuring the fluorescence signal as a function of the angle of incidence. In this study, two samples were intentionally contaminated with copper in non-deoxygenated and deoxygenated ultrapure water (UPW) resulting in impurity profiles that were either atomically dispersed in a thin film or particle-like, respectively. The concentration profile of the samples immersed into deoxygenated UPW was calculated using a theoretical concentration profile representative of particles, yielding a mean particle height of 16.1 nm. However, the resulting theoretical profile suggested that a distribution of particle heights exists on the surface. The fit of the angular distribution data was further refined by minimizing the residual error of a least-squares fit employing a model with a Gaussian distribution of particle heights about the mean height. The presence of a height distribution was also confirmed with atomic force microscopy measurements.

Nanometer-scale defects on the surface of a Si wafer, fabricated by nanoindentation technique, were examined using Raman microscopy and scanning surface potential microscopy to determine the quantitative relation between surface potential shift and Raman shift. Formation of cracks has not observed at the defect sites, indicating that the plastic and elastic deformations were a major issue and that the residual stress from the plastic deformation was observed. The Raman peak of the array of defects formed by nanoindentation shifted to a lower wavenumber as the indentation force was increased. The results indicated that the amount of tensile strain increased with the indentation force, that is, tensile stress was dominant over the condition in the surrounded area, in the indentation-induced defects. Correspondingly, the surface potential of the defect arrays shifted to the negative direction with an increase in indentation force. These results suggest that the tensile stress at the defect site, indicated by the Raman shift, causes the negative shift in the surface potential, which is related to chemical reactivity. Furthermore, Raman shift of a single indent on a silicon-on-insulator (SOI) wafer was observed, which revealed an enhancement in the source-to-noise ratio of the Raman spectrum at the Si defect site, because the ratio of the volume of the defect site to that of the unstrained site increased due to the thin Si layer on the SOI wafer.

Elementary steps in the electrochemical reduction process of SiCl4 in trimethyl-n-hexylammonium bis(trifluoromethylsulfonyl) imide (TMHATFSI) was investigated, focusing on molecular level behavior of the reactants at solid-liquid interface. Electrochemical measurements using an electrochemical quartz crystal microbalance (EQCM) identified a reduction peak corresponding to Si electrodeposition and several elementary steps with stable intermediates forming prior to the deposition. For detailed analysis, X-ray reflectivity (XRR) measurements with synchrotron radiation were applied in situ. The change in reflectivity of the electrode surface during the deposition was found to be due to the formation of a polymer-like Si such as Si2Cl6, which is an intermediate layer during the deposition process. These results were theoretically supported by density functional theory (DFT) calculations: after an electron transfers from the electrode, the Si in SiCl4 forms the bond with another SiCl4, rather than the Si of the substrate, resulting in the formation of the intermediate structure. These data suggest an elementary step in the SiCl4 reduction process which can be described as follows
when SiCl4 is reduced, a polymer-like Si form such as Si2Cl6 is generated. This intermediate species further reacts with other Si reactants after receiving additional electrons, which then finally deposits as Si on the substrate.

<p>New technique for analyzing buried interface has developed based on surface-enhanced Raman scattering spectroscopy. It consists of plasmonic sensors and spectrometer equipped with high precision mechanisms. Performance of the system involves in-situ measurement of interfaces, i.e. liquid/solid or solid/solid, with high sensitivity and high depth resolution on a variety of samples. Additional functions are in-situ temperature measurement by anti-Stokes/Stokes ratio, simultaneous acquisition with laser heating, time-resolved measurement, and pulsed laser Raman spectroscopy. A depth profile of layered ultra-thin films, i.e. diamond-like carbon (DLC) or highly oriented pyrolytic graphite (HOPG), was analyzed in atomic scale resolution at solid/solid interface. Molecular configuration and bonding feature of liquid organic molecules, i.e. lubricants for magnetic disks or reducing agents for a plating, were analyzed at liquid/solid interface. Oxidation process or decomposition process of ultra-thin DLC films was analyzed for a variety of DLC films. Spectral change with irradiation time by pulsed laser heating exhibited a kinetic change of molecular structures in a chemical reaction with in-situ heating temperature measurement.</p>

Electrolytic production process for solar-grade Si utilizing liquid Si-Zn alloy cathode in molten CaCl2 has been proposed. Toward the establishment of the process, the behavior of liquid Zn metal was investigated in molten CaCl2 at 1123 K. The evaporation of Zn metal was largely suppressed by an immersion into molten salt, which enables the use of Zn electrode in spite of the high vapor pressure of Zn. The cyclic voltammetry suggested the reduction of SiO2 at 1.45 V vs. Ca2+/Ca on a Zn cathode. After the potentiostatic electrolysis at 0.9 V, Si particles with diameters of 2-30 mu m were precipitated in the solidified Zn matrix by the slow cooling process of the produced liquid Si-Zn alloy. The alloying rate between solid Si and liquid Zn was measured as 4.56 mu m s(-1), and it linearly decreased with the Si content in liquid Zn phase.

Toward an establishment of a new production method of solar cell substrates, electrodeposition of Si was investigated in molten KF-KCl (eutectic composition, 45:55 mol%) after the introduction of SiCl4. Gaseous SiCl4 was directly introduced into the molten salt at 1023 K by a vapor transport method using Ar carrier gas. The dissolution ratio of SiCl4 exceeded 80% even with the use of a simple tube for the bubbling. Galvanostatic electrolysis was conducted at 923 K on a Ag substrate at 155 mA cm(-2) for 20 min in molten KF-KCl after the dissolution of 2.30 mol% SiCl4. Although compact Si layer was formed, the smoothness was lower compared to that obtained from the melt after the addition of K2SiF6. The anionic molar fraction is probably one of the factors affecting the morphology of deposit.

Toward an establishment of a new production method of solar cell substrates, electrodeposition of Si was investigated in molten KF-KCl (eutectic composition, 45:55 mol%) after the introduction of SiCl4. Gaseous SiCl4 was directly introduced into the molten salt at 1023 K by a vapor transport method using Ar carrier gas. The dissolution ratio of SiCl4 exceeded 80% even with the use of a simple tube for the bubbling. Galvanostatic electrolysis was conducted at 923 K on a Ag substrate at 155 mA cm(-2) for 20 min in molten KF-KCl after the dissolution of 2.30 mol% SiCl4. Although compact Si layer was formed, the smoothness was lower compared to that obtained from the melt after the addition of K2SiF6. The anionic molar fraction is probably one of the factors affecting the morphology of deposit.

Electrolytic production process for solar-grade Si utilizing liquid Si-Zn alloy cathode in molten CaCl2 has been proposed. Toward the establishment of the process, the behavior of liquid Zn metal was investigated in molten CaCl2 at 1123 K. The evaporation of Zn metal was largely suppressed by an immersion into molten salt, which enables the use of Zn electrode in spite of the high vapor pressure of Zn. The cyclic voltammetry suggested the reduction of SiO2 at 1.45 V vs. Ca2+/Ca on a Zn cathode. After the potentiostatic electrolysis at 0.9 V, Si particles with diameters of 2-30 mu m were precipitated in the solidified Zn matrix by the slow cooling process of the produced liquid Si-Zn alloy. The alloying rate between solid Si and liquid Zn was measured as 4.56 mu m s(-1), and it linearly decreased with the Si content in liquid Zn phase.

Theoretical analyses of L-alanine (L-Ala)- and L-homocysteine (L-Hcy)-Cu(II) complexes in basic, neutral, and acidic solutions were carried out using density functional theory to investigate the pH dependence of the formation mechanism of amino acid-Cu(II) complexes. The calculated complex formation energies indicate that the amino acid-Cu(II) complexes were expected to form in basic and neutral solutions but not in acidic solutions. The factors that determine the stability of these complexes are the coordination ability of each amino acid and the significance of intramolecular interactions among ligands within the complexes. As predicted from the molecular structure, in neutral solutions, the coordination ability of amino acid becomes lower than that in basic solutions because of the inert structure of the protonated amino group, -NH3+; however, the coordination ability originating from the -COO- group is estimated to be sufficient for stabilizing the entire complex system. Moreover, two H2O molecules coordinate with the central Cu2+ ion from the equatorial direction and interact with the coordinating amino acids, providing additional stability within the complex. In contrast, in acidic solutions, the complex does not have either sufficient coordination ability of amino acids or effective intramolecular interactions within the complex.

A heat-assisted magnetic recording (HAMR) is expected for a future high density recording of a hard disk drive. However, a. carbon overcoat (COC) composed of diamond-like carbon (DLC) or a lubricant film is possibly damaged when a magnetic medium, i.e. CoPt alloy, is heated at around Curie temperature (Tc) of 600K by a near-field HAMR head. We carried out HAMR. simulation experiments by using newly developed Raman spectroscopic systems, composed of plasmonic sensors for surface-enhanced Raman scattering (SERS), a pulsed laser heating, and an in-situ temperature measurement with an intensity ratio of anti-Stokes/Stokes lines. It was found that the heated temperature of the COC is higher than that of the magnetic film, i.e., 580 degrees C and 366 degrees C, respectively. Intensity changes of G-band peak in Raman spectra for DLC films were observed during the pulsed laser heating. The Raman intensity was exponentially decreased by oxidation in air, where time constants were calculated as a parameter of a pulse width. Degradation life of the DLC film can be estimated from a critical pulse width, where the time constant is extrapolated to zero. The estimated pulse width for no degradation was 250 mu s at the heating temperature of 580 degrees C. The result shows no damage can be estimated in DLC films for HAMR. because the effective irradiation time is 5ns and the accumulated irradiation time is 0.5ms in HAMR operations.

A chemical depth profile in lubricant films, carbon films, and their interfaces is an informative parameter for hard disk media because molecular features of lubricants bonded to a surface of carbon overcoats (COCs), which usually consist of a nitrogen doped layer, are important to achieve high tribological performance. However, it was difficult to analyze their interfaces with high depth resolution because thickness of lubricant films and COC films are so thin, i.e. 1.5nm and 2nm, respectively. We have developed new method using plasmonic sensors, which has measurement capability for chemical structures with depth resolution of 0.1nm by surface-enhanced Raman spectroscopy (SERS). We examined the lubricant film composed of perfluorinated polyether (PEPE) with phosphazene derivative (A2OH) on a diamond-like carbon (DLC) film. The result shows that the functional group is adsorbed on the DLC surface, where lower shift in the wave number of phenyl group is observed. The depth profile of the intensity ratio of D-peak to G-peak shows the maximum at around the surface of the DLC film. A variety of organic components in the DLC films, fabricated by a chemical vapor deposition (CVD), were observed in it. Besides, the depth profiles shows that organic materials, involving methyl, ethyl, or ethylene groups, Co(OH)x exist in the film

© Copyright 2016 by ASME.A heat-assisted magnetic recording (HAMR) is expected for a future high density recording of a hard disk drive. However, a carbon overcoat (COC) composed of diamond-like carbon (DLC) or a lubricant film is possibly damaged when a magnetic medium, i.e. CoPt alloy, is heated at around Curie temperature (Tc) of 600K by a near-field HAMR head. We carried out HAMR simulation experiments by using newly developed Raman spectroscopic systems, composed of plasmonic sensors for surface-enhanced Raman scattering (SERS), a pulsed laser heating, and an in-situ temperature measurement with an intensity ratio of anti-Stokes/Stokes lines. It was found that the heated temperature of the COC is higher than that of the magnetic film, i.e., 580°C and 366°C, respectively. Intensity changes of G-band peak in Raman spectra for DLC films were observed during the pulsed laser heating. The Raman intensity was exponentially decreased by oxidation in air, where time constants were calculated as a parameter of a pulse width. Degradation life of the DLC film can be estimated from a critical pulse width, where the time constant is extrapolated to zero. The estimated pulse width for no degradation was 250μs at the heating temperature of 580°C. The result shows no damage can be estimated in DLC films for HAMR because the effective irradiation time is 5ns and the accumulated irradiation time is 0.5ms in HAMR operations.

We attempted to form ZnO films with smooth surface for the application of thermoelectric micro-devices, using electrodeposition process. In order to reduce the defects of the films such as cracks and pits mainly caused by the gas evolution, the bath containing acetate in addition to nitrate ions was developed to reduce the gas evolution during the deposition. Using this bath, formation of ZnO. rather than Zn metallic films, was confirmed by Raman spectroscopy. The films had no cracks and the surface became smoother than those eiectrodeposited from the conventional nitrate-based bath. In order to fabricate the micro- devices, The ZnO was eiectrodeposited into the patterns with diameter of 200μm. As a result, ZnO successfully filled the pattern keeping the smooth surface conditions, which demonstrated the applicability of the ZnO films to micro-device fabrication.

© Copyright 2016 by ASME.A chemical depth profile in lubricant films, carbon films, and their interfaces is an informative parameter for hard disk media because molecular features of lubricants bonded to a surface of carbon overcoats (COCs), which usually consist of a nitrogen doped layer, are important to achieve high tribological performance. However, it was difficult to analyze their interfaces with high depth resolution because thickness of lubricant films and COC films are so thin, i.e. 1.5nm and 2nm, respectively. We have developed new method using plasmonic sensors, which has measurement capability for chemical structures with depth resolution of 0.1nm by surface-enhanced Raman spectroscopy (SERS). We examined the lubricant film composed of perfluorinated polyether (PFPE) with phosphazene derivative (A2OH) on a diamond-like carbon (DLC) film. The result shows that the functional group is adsorbed on the DLC surface, where lower shift in the wave number of phenyl group is observed. The depth profile of the intensity ratio of D-peak to G-peak shows the maximum at around the surface of the DLC film. A variety of organic components in the DLC films, fabricated by a chemical vapor deposition (CVD), were observed in it. Besides, the depth profiles shows that organic materials, involving methyl, ethyl, or ethylene groups, Co(OH)x exist in the film.

To elucidate the catalytic reaction mechanism of BH₄^－ (a reducing agent) on metal surfaces during electroless deposition, its oxidation reaction was investigated theoretically using density functional theory (DFT) calculation. Particularly in this study, dehydrogenation reaction of BH₄^－ was modeled and analyzed because it is the most important elementary step of overall oxidation for the catalytic behavior of metal surfaces. To ascertain the tendencies of catalytic activity of metal surfaces, the reaction on Cu(111) and that on Pd(111) were compared. Actually, Cu shows little catalytic activity toward BH₄^－ oxidation, whereas Pd shows strong catalytic activity. Results of reaction energy calculations show that the BH₄^－ dehydrogenation occurs with difficulty on Cu(111), but it occurs easily on Pd(111), which corresponds to experimental results. Detailed analyses of reaction system electronic structures show that the d-band states of each surface are important to assess the background of the difference. Because the Pd surface has a high-energy d-band, it can interact with high-energy unoccupied orbitals of BH₄^－, leading to electron donation from the surface toward BH₄^－. This electron donation effect from Pd provides dissociation activity of the B-H bond, which promotes dehydrogenation of BH₄^－.

The reaction mechanism of Si electrodeposition in the ionic liquid trimethyl-n-hexylammonium bis (trifluoromethylsulfonyl) imide (TMHATFSI) with SiCl4 was investigated using an electrochemical quartz crystal microbalance (EQCM) and X-ray photoelectron spectroscopy (XPS). The deposited films were further characterized by Raman spectroscopy. The EQCM method measured the frequency change in situ during electrodeposition, whereas XPS provided the Si mass concentration in the electrodeposited films. By combining these results, the mass change due to SiCl4 reduction was estimated. Then, the current efficiency for Si electrodeposition at various potentials was evaluated. The calculated current efficiency was almost 100% when it was assumed that SiCl4 reduction progressed by four-electron electroreduction. The XPS and Raman results showed that the deposited films were composed primarily of amorphous Si with Si-Si bonds. Crystalline Si thin films were obtained after annealing in an Ar gas stream. (C) 2015 Elsevier Ltd. All rights reserved.

The reaction mechanism of Si electrodeposition in the ionic liquid trimethyl-n-hexylammonium bis (trifluoromethylsulfonyl) imide (TMHATFSI) with SiCl4 was investigated using an electrochemical quartz crystal microbalance (EQCM) and X-ray photoelectron spectroscopy (XPS). The deposited films were further characterized by Raman spectroscopy. The EQCM method measured the frequency change in situ during electrodeposition, whereas XPS provided the Si mass concentration in the electrodeposited films. By combining these results, the mass change due to SiCl4 reduction was estimated. Then, the current efficiency for Si electrodeposition at various potentials was evaluated. The calculated current efficiency was almost 100% when it was assumed that SiCl4 reduction progressed by four-electron electroreduction. The XPS and Raman results showed that the deposited films were composed primarily of amorphous Si with Si-Si bonds. Crystalline Si thin films were obtained after annealing in an Ar gas stream. (C) 2015 Elsevier Ltd. All rights reserved.

The reaction mechanism of Si electrodeposition in the ionic liquid trimethyl-n-hexylammonium bis (trifluoromethylsulfonyl) imide (TMHATFSI) with SiCl4 was investigated using an electrochemical quartz crystal microbalance (EQCM) and X-ray photoelectron spectroscopy (XPS). The deposited films were further characterized by Raman spectroscopy. The EQCM method measured the frequency change in situ during electrodeposition, whereas XPS provided the Si mass concentration in the electrodeposited films. By combining these results, the mass change due to SiCl4 reduction was estimated. Then, the current efficiency for Si electrodeposition at various potentials was evaluated. The calculated current efficiency was almost 100% when it was assumed that SiCl4 reduction progressed by four-electron electroreduction. The XPS and Raman results showed that the deposited films were composed primarily of amorphous Si with Si-Si bonds. Crystalline Si thin films were obtained after annealing in an Ar gas stream. (C) 2015 Elsevier Ltd. All rights reserved.

A new approach to produce high purity solar grade silicon (SOG-Si) using wet-chemical and electrochemical processes was proposed. First, diatomaceous earth was used as a source of silica and wet-chemical purification by acid leaching and solvent extraction processes were applied for eliminating heavy metal and light element such as boron, respectively. In particular, the solvent extraction using channel flow reactor demonstrated extremely high efficiency for eliminating boron to 7N (99.99999%) level purity. Secondly, the high-purity silica was reduced to silicon by the direct electrolysis method using molten CaCl2 as an electrolyte and Si plate as cathode. We proposed the continuous electrolysis system by feeding silica granules to the Si cathode set at the bottom of the cell. It was confirmed that the reduction proceeded steadily to form crystalline Si with a sufficient reduction rate. We also attempted electrodeposition of Si films and have developed a process using KF-KCl + K2SiF6 molten salt, from which uniform layer of Si with a thickness larger than 100 mu m could be formed. (C) 2015 Elsevier Ltd. All rights reserved.

Electrochemical approaches for the fabrication of functional micro–nano structures and devices were comprehensively described primarily on the basis of the results obtained from previous studies conducted by the author's group with the aim of demonstrating the potential for achieving further precise controllability. First, a theoretical study was conducted for investigating the processes, mainly focusing upon electroless deposition to present an approach for analyzing its reaction mechanism from the molecular level. These approaches could be powerful tools for elucidating the overall process and could contribute toward achieving the precise design of processes. Second, some experimental approaches for achieving the precise control of micro–nano fabrication of functional structures, such as maskless and electroless fabrication of metal nano-patterns, lateral enhanced electrodeposition to form ultrathin layers, as well as the nanostructures for various devices by through-mask electrochemical deposition, were introduced to demonstrate high capability of the processes for nanoscale fabrication in various applications.

Electrochemical approaches for the fabrication of functional micro-nano structures and devices were comprehensively described primarily on the basis of the results obtained from previous studies conducted by the author's group with the aim of demonstrating the potential for achieving further precise controllability. First, a theoretical study was conducted for investigating the processes, mainly focusing upon electroless deposition to present an approach for analyzing its reaction mechanism from the molecular level. These approaches could be powerful tools for elucidating the overall process and could contribute toward achieving the precise design of processes. Second, some experimental approaches for achieving the precise control of micro-nano fabrication of functional structures, such as maskless and electroless fabrication of metal nano-patterns, lateral enhanced electrodeposition to form ultrathin layers, as well as the nanostructures for various devices by through-mask electrochemical deposition, were introduced to demonstrate high capability of the processes for nanoscale fabrication in various applications. (C) The Electrochemical Society of Japan, All rights reserved.

A new method for electroplating Si using a water-soluble KF-KCl molten salt electrolyte and high-purity gaseous SiCl4 has been proposed. To gain a fundamental understanding of the process, the electrodeposition of Si from Si(IV) complex ions on a Ag electrode in a molten KF-KCl-K2SiF6 system was investigated by cyclic voltammetry at 923 K. The reduction of Si(IV) ions to metallic Si was observed as a single 4-electron wave, which is explained by an EqEr (quasireversible-reversible electron transfer reactions) mechanism. The diffusion coefficient of the Si(IV) ions in the electrolyte was determined to be 3.2 x 10(-5) cm(2) s(-1) at 923 K by chronoamperometry. (C) 2015 The Electrochemical Society. All rights reserved.

To establish a new Si-electrodeposition process, the optimum conditions for obtaining adherent, compact, and smooth Si films using molten KF-KCl-K2SiF6 were investigated at 923 K. Galvanostatic electrolysis was conducted on a Ag substrate in eutectic KF-KCl (45:55 mol%) with various current densities (10-500 mA cm(-2)) and K2SiF6 concentrations (0.5-5.0 mol%). Cross-sectional scanning electron microscopy (SEM) of the deposits revealed that compact and smooth Si films form at intermediate K2SiF6 concentrations and current densities. The relationship between the deposition conditions and Si morphology is discussed in terms of the electrodeposition mechanism. (C) 2015 The Electrochemical Society. All rights reserved.

Elimination of boron species via solvent extraction with 2,2,4-trimethyl-1,3-pentandiaol was engaged in a flow-type device into which the aqueous solution dissolving diatomaceous earth, a -candidate of the resource for high-purity silicon material. The flow-type device has a 2-stage channel with 1.0 mm width, 0.10 mm depth, and 25 mm length each, and the specific interfacial area is comparable to a typical microchannel device. Residual boron content in the aqueous solution decreased to less than 0.1 ppm after the solvent extraction under the restriction of short contact duration shorter than 100 ms. In addition, the analysis with density functional theory indicated that the number of neighbor carbon on the central carbon is one of the keys for improvement of reactivity of extractant. Hence, it is suggested that the flow-type microchannel device with solvent extraction with alkyldiol extractant can be utilized as an attractive approach toward the production of high-purity silica as a source for solar-grade silicon.

We have fabricated Co-Pt nanodot arrays by electrochemical process for the application of bit patterned media (BPM), which is proposed as a key technology for future recording media. Since formation of uniform nanodot arrays is required for BPM, controlling the initial stages of electrodeposition is significant. In this work, we analyzed the effects of applied potential and size of nano-patterns on initial stages of Co-Pt electrodeposition. As a result, number of Co-Pt nuclei decreased in smaller nano-pore. In particular, formation of Co-Pt single grains, which exhibit high and uniform coercivity, was expected with low overpotential in nanopore with 10 nm diameter. Furthermore, coercivities of Co-Pt films at the initial stage increased with lower overpotential, since Co-Pt nucleated and grew along with Ru underlayer with high orientation. These results indicate that magnetic properties of Co-Pt nanodot arrays can be optimized by controlling the nucleation and growth behavior of Co-Pt.

A Pi-structured Bi-Te micro-thermoelectric device with a large upper electrode, i.e., an umbrella-type device, was fabricated via electrodeposition, and the effect of the size of the electrode was evaluated. The Bi-Te thermoelectric materials were electrodeposited from HNO3-based aqueous electrolyte. The device consisted of eight arrays, each consisting of 110 thermoelectric units, each of which was electrodeposited onto the patterned substrate with an array of 50 x 50 mu m(2) holes that were 20 mu m deep. The deposition conditions for the n-type and p-type Bi-Te films were optimized to enable patterned electrodeposition of the materials to yield dense and uniform deposits. Accordingly, the materials were selectively deposited in a pattern to fabricate the thermoelectric micro-device. The resultant umbrella-type device, whose electrode is 1.65 times larger than smaller electrode, generated 4.57 times more power than the device with a smaller electrode. Therefore, we confirmed the improvement power by using an umbrella-type device. (C) 2014 Elsevier Ltd. All rights reserved.

TiO2 nanotubes are widely investigated materials for photoelectrochemical water splitting, but the presence of trap states limits their performance by facilitating the recombination of electron/hole pairs. In this investigation we unequivocally demonstrate that the photocurrent improvement observed in TiO2 nanotubes after performing electrochemical doping with hydrogen or lithium ions is due to trap state passivation. Specifically, electrochemical impedance spectroscopy evidences that trap state defects disappear upon electrochemical doping, concurrent with an increase in the electron lifetime and faster photocurrent transients. This results in a two-fold enhancement in the photocurrent under simulated sunlight at 1.0 V vs. SCE. Li intercalation was confirmed and the structure as well as the composition of the modified nanotubes was elucidated by GDOES, XPS, and TEM.

TiO2 nanotubes are widely investigated materials for photoelectrochemical water splitting, but the presence of trap states limits their performance by facilitating the recombination of electron/hole pairs. In this investigation we unequivocally demonstrate that the photocurrent improvement observed in TiO2 nanotubes after performing electrochemical doping with hydrogen or lithium ions is due to trap state passivation. Specifically, electrochemical impedance spectroscopy evidences that trap state defects disappear upon electrochemical doping, concurrent with an increase in the electron lifetime and faster photocurrent transients. This results in a two-fold enhancement in the photocurrent under simulated sunlight at 1.0 V vs. SCE. Li intercalation was confirmed and the structure as well as the composition of the modified nanotubes was elucidated by GDOES, XPS, and TEM.

The electrochemical reduction behavior of stratified SiO2 granules in molten CaCl2 at 1123 K (850 A degrees C) was investigated to develop a new process for producing solar-grade silicon. The cross sections of the electrolyzed electrode prepared from a graphite crucible filled with SiO2 granules were observed and analyzed. The visual and SEM observations indicate that the overall reduction proceeds via two different routes. In one route, the reduction proceeds along the granule surfaces from the SiO2 near the conductor to the distant SiO2. In the other route, the reduction proceeds from the granule surface to the core of each granule. The reduction along the granule surfaces is faster than that from the surface to the core. Fine SiO2 granules are expected to be favorable for a high reduction rate. (C) The Minerals, Metals & Materials Society and ASM International 2014

The kinetic characteristics of electrochemical reduction of SiO2 granules in molten CaCl2 were investigated to develop a new process for producing solar-grade silicon. The reduction rate was-evaluated based-on-the time dependence of the reduction fractions measured from the growth of the reduced Si layer and the weight change of the samples during electrolysis. The samples were prepared by potentiostatic electrolysis of SiO2 granules in molten CaCl2 at 1123 K. The results indicated that the reduction was fast at the initial stage of electrolysis, and gradually slowed as the reaction progressed. The apparent current density reached 0.7 A cm(-2) at the initial stage, which was comparable to the commercial Hall-Heroult process for aluminum production. (C) 2014 The Electrochemical Society. All rights reserved.

A novel approach toward the purification of silica and removal of boron impurities via solvent extraction with 2-ethyl-1,3-hexanediol using a microchannel device is presented. The microchannel, fabricated on Si substrates using lithographic techniques, had 100 mu m width, 100 mu m depth, and 10 mm length. Amorphous silica spiked with a trace amount of boric acid and refined diatomaceous earth used as silica feedstock were purified. Residual boron content was determined by inductively coupled argon plasma atomic emission spectrometry. Following extraction using a microchannel device, the residual boron content was less than 1.0 ppm for the former silica feedstock and than 2.5 ppm for the latter one, and the contact reaction period was 0.03 seconds for both type of silica feedstock. These are lower and significantly shorter due to much shorter diffusion distance and much larger specific interfacial area as compared to those observed when using a conventional separatory funnel, for both types of silica feedstock. Hence, it is suggested that microchannel devices can be utilized as an attractive approach toward the production of high-purity silica as a source for solar-grade silicon. (C) 2014 The Electrochemical Society. All rights reserved.

A NiP imprinting mold with patterns, whose size is from nanometer to submicrometer (170, 500, and 1000nm diameter), was fabricated by electroless deposition of NiP on a 3-aminopropyltriethoxysilane (APTES) modified master mold. The NiP deposit as a replicate mold was then detached from the master mold. The initial NiP deposition in patterns of the master mold was investigated
moreover, nanoindentation was successfully performed on a single NiP pattern for investigating the hardness. The NiP had a similar grain size in different sizes of patterns of the master mold during the initial deposition, as well as the same hardness of the NiP patterns (approximately 12 GPa) was observed. These results indicated that the initial NiP deposition and hardness of NiP were not size dependent above 170 nm. The surface morphology of the NiP detached from the master mold and NiP pattern of different sizes were investigated as well. © 2013 The Japan Society of Applied Physics.

We fabricated hcp-Co_<80>Pt_<20> and L1_0-FePt thin films and nanodot arrays onto hcp-Ru (002) / Si substrate by electrodeposition and lithography processes. The effect of applied potential and diameter of the nanodot on deposition behavior of Co-Pt was analyzed in order to control the deposition of Co-Pt. By using electron beam lithography, nanodot patterns with 10 nm diameter and 18 nm pitch were uniformly fabricated. It was suggested that the particle size of Co-Pt could be controlled by the applied potential, and in the case of relatively positive applied potential of -400 mV and -500 mV vs Ag / AgCl, progressive nucleation preferentially occurred to increase the size of each Co-Pt particle. The phase transformation from fcc-Fe-Pt to L1_0 Fe-Pt was observed by annealing at 650℃, and Fe-Pt films with perpendicular coercivity of 9.0 kOe and 9.8 kOe with a thickness of 10 nm and 25 nm were obtained. In addition, Fe-Pt nanodot arrays having a pitch and a diameter of 100 nm and 35 nm were successfully fabricated by UV-nanoimprint lithography.

Oxidation of the reductants is a dominant factor in the electroless deposition process. In order to obtain fundamental knowledge about the reaction mechanism of reductant oxidation for more precise control of the solid-liquid interface in this process, we have attempted to characterize the behavior of reductants adsorbed on Cu surface by using plasmon antenna enhanced Raman scattering. The concentric-patterned antenna coated with Cu, which consisted of a dimple array with single hole or a single hole with coaxial dimples, was designed by Finite Difference Time Domain (FDTD) calculation to enhance the electric field by focusing surface plasmons. By using this antenna and comparing the spectra to the results of Density Functional Theory (DFT) calculations, Raman peaks of adsorbed reductants on Cu were identified. Furthermore, we examined the conformation of adsorbed reductants by DFT calculation of the adsorption model of reductants on fcc-Cu(111) surface. As a result, the nature of reductant adsorption on Cu surface has been investigated from a computational point of view and an experimental point of view, and such in-situ characterization will be useful for analysis of a variety of systems at solid-liquid interface. (c) The Electrochemical Society of Japan, All rights reserved.

An electroless NiP imprinting mold was fabricated through replication of a cyclo-olefin polymer (COP) master mold. The NiP was electrolessly deposited on a nanopatterned COP master mold, pretreated by ultraviolet (UV) irradiation prior to modification with 3-aminopropyltriethoxysilane (APTES). The NiP deposit as a "replicate" was then detached from the COP master mold. Additionally, by optimizing the UV irradiation period, APTES could be formed on the COP master mold for electroless deposition without disturbing the nanopattern geometry of the COP master mold. The water contact angle and surface morphology of the COP surface, and the adhesion strength between deposited NiP and the COP surface were investigated. © 2013 The Electrochemical Society of Japan, All rights reserved.

Direct electrolytic reduction of SiO2 was investigated in molten CaCl2 at 1123K as a fundamental study to develop a continuous process for solar-grade Si production. Several different types of SiO 2 granules, as well as SiO2 pellets, were successfully reduced to Si on the bottom cathode of a Si plate. Three parameters were varied in the reduction of SiO2 granules: electrode potential, layer thickness of the SiO2 granules, and SiO2 particle size. The reduction rate was evaluated by the magnitude of the reduction current. The main factor determining the reduction rate was the diffusion of O2- ions inside the reduced porous Si layer filled with the electrolyte. Another factor which influenced the reduction rate was the contact resistance between Si granules. © The Electrochemical Society of Japan 2013.

We have been fabricating ferromagnetic nanodot arrays for bit patterned media (BPM) by using lithography techniques and electrochemical processes. In this research, we attemped to fabricate hcp-Co-Pt(002) and L10-Fe-Pt thin films and nanodot arrays with high coercivity. Nano-patterns were formed by electron beam lithography (EBL) and Co-Pt and Fe-Pt were electrodeposited into the nano-patterns. For obtaining Co-Pt thin films and nanodot arrays with high perpendicular coercivities, we applied hcp-Ru(002) intermediate layer on Si substrate. As a result, the magnetic properties and the crystallinities of Co-Pt thin films and nanodot arrays were improved by using Ru(002) layer, and Co-Pt nanodot arrays with 10 nm diameters and 18 nm pitches were observed. Investigation of initial deposition suggested that the particle size of Co-Pt can be controlled by changing the applied potential. The phase transformation from fcc-Fe-Pt to L1_0-Fe-Pt was verified by annealing, and the coercivities of Fe-Pt were improved.

The electrodeposition of silicon from silicon tetrachloride in the hydrophobic room temperature ionic liquid trimethyl-n-hexyl ammonium bis-(trifluoromethylsulfonyl) imide was investigated by cyclic voltammetry and chronoamperometry. In situ electrochemical quartz crystal microbalance (EQCM) impedance spectroscopy was used to estimate the mass of films during deposition. The charge efficiency estimated from EQCM measurements is similar to 190-250% for four-electron silicon reduction. However, compositional analysis by XPS shows that the EQCM current efficiency estimates are artificially high due to ionic liquid inclusion in the films. Taking the mass concentration of impurities into account, the bestcase estimate of current efficiency is found to be approximately 130% for constant potential deposition, suggesting silicon may not have been completely reduced at the potentials investigated, or a chemical reaction step occurs. We also consider that the EQCM analysis may include too many deviations from assumptions for accurate estimation of mass with the conditions studied. (C) 2012 Elsevier Ltd. All rights reserved.

The electrodeposition of silicon from silicon tetrachloride in the hydrophobic room temperature ionic liquid trimethyl-n-hexyl ammonium bis-(trifluoromethylsulfonyl) imide was investigated by cyclic voltammetry and chronoamperometry. In situ electrochemical quartz crystal microbalance (EQCM) impedance spectroscopy was used to estimate the mass of films during deposition. The charge efficiency estimated from EQCM measurements is similar to 190-250% for four-electron silicon reduction. However, compositional analysis by XPS shows that the EQCM current efficiency estimates are artificially high due to ionic liquid inclusion in the films. Taking the mass concentration of impurities into account, the bestcase estimate of current efficiency is found to be approximately 130% for constant potential deposition, suggesting silicon may not have been completely reduced at the potentials investigated, or a chemical reaction step occurs. We also consider that the EQCM analysis may include too many deviations from assumptions for accurate estimation of mass with the conditions studied. (C) 2012 Elsevier Ltd. All rights reserved.

This paper described characterization of hydrazine adsorption on Cu surface with high-selectivity of component at right angle down to single molecular level using a plasmonic antenna enhancing Raman scattering. The antenna deposited by Cu with concentric pattern was designed by Finite Difference Time Domain (FDTD) calculation to enhance the electric field by focusing surface plasmon. By using this antenna, Raman peaks of adsorbed hydrazine on Cu was provided at 385 cm(-1). Furthermore, these peaks were only observed at 1-2 nm from the antenna surface which meant that this approach had a potential to define the structure of adsorbed hydrazine just only on the plasmon antenna. The structure of adsorbed hydrazine was gauche-conformation. This data corresponded to the Density Functional Theory (DFT) of adsorption model of hydrazine on fcc-Cu (1 1 1) surface. These results suggest that this method creates a wide range of spin-off effects to the characterization of solid-liquid interface. (c) 2012 Elsevier Ltd. All rights reserved.

The TiO2 nanotube system exhibits properties of interest in photoelectrochemical water splitting for hydrogen production, including high surface area and vectorial charge transport along the nanotube length. Changes in the anodizing electrolyte chemistry provide the means to control nanotube morphology as well as their length and width. Despite the large amount of work available on nanotube synthesis, however, a thorough assessment of the effect of anodization conditions on the photoelectrochemical performance is still unavailable. In this paper, we characterize TiO2 nanotubes produced by varying the water content of the organic anodization electrolyte and investigate the influence of the electrolyte on their photoelectrochemical performance. We find that the photocurrent efficiency of the nanotubes is optimized by using an 11 vol % water:ethylene glycol ratio. We also demonstrate that a double-anodization technique produces a cleaner surface, resulting in higher photon-to-current conversion efficiencies of up to 30% at 350 nm. Raman spectroscopy, X-ray diffraction, and electrochemical impedance studies support the notion that the variation in crystallinity as a function of water content is the main factor in determining the photocurrent efficiency of the nanotube system.

We demonstrated fabrication of nanogap electrodes with flat and thin Au films by using laterally enhanced growth of Au electrodeposition and applied the electrodes for electrical measurement of poly(3-methylthiophene) (P3MT) nanowires. The Au electrodeposition was performed on nnicrogap electrodes following an organic modification process on an insulator surface of the microgap electrodes. Then, P3MT nanowires were aligned between the nanogap electrodes for transistor property measurement. The result suggested that the fabricated nanogap electrodes were suitable to apply for electrical properties measurement of such organic nanowires because of small difference in height between top of the electrodes and the insulator surface. (C) The Electrochemical Society of Japan, All rights reserved.

Mechanical stress was applied to a Si single crystal wafer to evaluate the changes in its surface properties arising from the lattice strain induced by mechanical stress. The stress was applied quantitatively to the wafer in order to investigate the correlation between the degree of strain and the electrochemical properties of its surface. Finite element method (FEM) structural analysis was used to estimate the degree of strain on the surface, and the open circuit potential was measured in order to investigate the surface electrochemical properties. The analysis suggested that the surface of the wafer was under tensile strain, and the open circuit potential shifted toward the negative direction with the strain. This indicates that mechanical stress applied to a Si surface can change its electronic properties by changing the surface crystal structure. (C) 2012 Elsevier B.V. All rights reserved.

A nanoimprint lithography mold was fabricated through electroless deposition combined with self-assembled monolayer (SAM) modification. To copy nanopatterns as "replicates", NiP was electrolessly deposited on a nanopatterned master mold (made of SiO2/Si), whose surface was modified with 3-[2-(2-aminoethylamino)ethylamino]propyltrimethoxysilane (TAS). NiP deposits were then manually detached from the mold. SAM improves Pd catalyst coverage for electroless deposition, further improving the morphology of the electroless deposition of NiP on the nanopatterned master mold and controlling the adhesion strength between electroless deposited NiP and the nanopatterned master mold to a level appropriate for smooth detachment. The initial catalyzation process and mechanical properties (such as, the hardness and adhesion strength of the SiO2 substrate) of electroless deposited NiP were also systematically investigated. (c) 2012 Elsevier Ltd. All rights reserved.

Mechanical stress was applied to a Si single crystal wafer to evaluate the changes in its surface properties arising from the lattice strain induced by mechanical stress. The stress was applied quantitatively to the wafer in order to investigate the correlation between the degree of strain and the electrochemical properties of its surface. Finite element method (FEM) structural analysis was used to estimate the degree of strain on the surface, and the open circuit potential was measured in order to investigate the surface electrochemical properties. The analysis suggested that the surface of the wafer was under tensile strain, and the open circuit potential shifted toward the negative direction with the strain. This indicates that mechanical stress applied to a Si surface can change its electronic properties by changing the surface crystal structure. (C) 2012 Elsevier B.V. All rights reserved.

A nanoimprint lithography mold was fabricated through electroless deposition combined with self-assembled monolayer (SAM) modification. To copy nanopatterns as "replicates", NiP was electrolessly deposited on a nanopatterned master mold (made of SiO2/Si), whose surface was modified with 3-[2-(2-aminoethylamino)ethylamino]propyltrimethoxysilane (TAS). NiP deposits were then manually detached from the mold. SAM improves Pd catalyst coverage for electroless deposition, further improving the morphology of the electroless deposition of NiP on the nanopatterned master mold and controlling the adhesion strength between electroless deposited NiP and the nanopatterned master mold to a level appropriate for smooth detachment. The initial catalyzation process and mechanical properties (such as, the hardness and adhesion strength of the SiO2 substrate) of electroless deposited NiP were also systematically investigated. (c) 2012 Elsevier Ltd. All rights reserved.

Chemical structure of ultra-thin lubricant film/DLC overcoat for 4Tbpsi and more was measured with plasmonic sensor and surface-enhanced Raman scattering spectroscopy. Depth profile of the chemical structure for the film system was also measured with a depth resolution of 0.1nm.

We investigated the laterally enhanced growth of electrodeposited Au for fabricating nanogap electrodes. To enhance the lateral growth, we carried out electrodeposition over patterned electrodes onto a SiO2 surface modified with self-assembled monolayers (SAMs) or dendrimers with amine groups. The morphology and thickness of the Au films were controlled by adjusting deposition conditions such as duration, applied potential, and Au ion concentration in the bath. To investigate the mechanism of the laterally enhanced growth, the surface states of SAM- or dendrimer-modified SiO2 were analyzed by X-ray photoelectron spectroscopy (XPS). The XPS results indicate the existence of organic molecules and Au ions on the SiO2 surface, which suggests that laterally enhanced growth is induced by the Au ions coordinated on the amine groups of the organic molecules. To further analyze the mechanism of the laterally enhanced growth, we investigated the relationship between the morphology of the laterally enhanced growth of Au and the amount of Au ions on organic molecules. The laterally enhanced growth of Au is expected to be useful for fabricating thin film nanogap electrodes. (C) 2012 Elsevier Ltd. All rights reserved.

The influence of water molecules on the reaction behavior of hypophosphite ion, which acts as a reducing agent for electroless deposition, on metal surfaces was elucidated by calculating the adsorption structure of hydrated hypophosphite ion on a Pd surface using Monte-Carlo simulation and density functional theory calculations. Through geometrical optimization, the most favorable structure of the hydrated hypophosphite ion was obtained, in which six water molecules interact with the oxygen of hypophosphite ion and no water interacts with the hydrogen of hypophosphite ion. Further calculations indicated that the hydrated hypophosphite ion adsorbed on the Pd surface via hydrogen. (C) The Electrochemical Society of Japan, All rights reserved.

To elucidate the mechanism of catalytic activity of metal surfaces on the reaction of hypophosphite ions, which act as a reducing agent for electroless deposition, molecular orbital interactions between hypophosphite ions and metal surfaces were analyzed using density functional theory. Pd (111) and Cu (111) were chosen as the surfaces with high and low catalytic activity, respectively. The electronic states of adsorption systems were analyzed using the Mulliken population analysis. The position of the d-band plays a key role in determining the catalytic activity on P-H bond cleavage of hypophosphite. The Pd surface has a d-band near the Fermi level and contains a vacancy; this enables the donation and back-donation effect to occur on the adsorbed hypophosphite and promotes P-H bond cleavage. On the other hand, the Cu surface has a d-band in the deep energy area and contains no vacancy; the donation and back-donation effect is not induced and P-H bond cleavage is not promoted. This difference in the degree of promotion of P-H cleavage is responsible for the difference in the catalytic activity on P-H cleavage and dehydrogenation of hypophosphite ions, which in turn explains the difference in the catalytic activity during the entire hypophosphite oxidation process. (C) The Electrochemical Society of Japan, All rights reserved.

An electroless deposition process for fabricating CoNiP nanodot arrays (less than 50 nm in height) with high magnetic coercivities was investigated. To fabricate such nanostructures, we improved the crystallinity of the CoNiP deposits in the initial deposition stage by applying an fcc-Cu(1 1 1) underlayer with low lattice mismatch to hcp-Co(0 0 0 2), and an autocatalytic electroless deposition process at the Cu surface was carried out by using dual reducing agents, H(2)PO(2)(-) and N(2)H(4). CoNiP films demonstrated high perpendicular magnetic coercivities in the initial deposition stage since the highly crystalline hcp(0 0 0 2) CoNiP layers were grown parallel to the Cu underlayers. Nanopatterned substrates were formed by UV-nanoimprint lithography. CoNiP was electroless deposited on the nanopatterned substrates. As a result. CoNiP was deposited selectively from the bottom of the nanopores with few defects in a large area. Perpendicular coercivities higher than 3000 Oe were obtained for nanodots even with heights of 50 nm. Thus, an electroless deposition process that can be used to form nanostructures with high crystallinities in the initial stage without any anomalous deposition was demonstrated. (C) 2011 Elsevier Ltd. All rights reserved.

Ultra-thin DLC films and lubricant films are requested for high density magnetic recording. It was difficult for Raman spectroscopy to measure their molecular structures because of its low sensitivity. Newly-developed plasmonic sensor successfully acquired Raman spectrum of DLC films or lubricant/DLC interfaces with sub-nanometer thickness. Crystal structure of ultra-thin DLC films were slightly changed compared with that of thick films. Specifically, a graphite-like structure increases with decreasing thickness. It was found that organic and inorganic contaminations exist on a magnetic layer or a magnetic layer/DLC interface. According to the Raman spectrum analysis, a feature of adsorbed lubricant molecules of lubricant on the DLC film was confirmed.

We investigated fabrication processes of magnetic nanodot arrays for the ultra-high density magnetic recording media by using an electrodeposition A CoZrNb underlayer was sputter-deposited on a glass disk substrate as a soft magnetic underlayer (SUL) Nano-patterns were formed on the substrate by UV-nanoimprint lithography (UV-NIL) and CoPt was electrodeposited into the nano-patterns For obtaining uniform CoPt nanodot arrays with high perpendicular coercivities we applied thin Cu intermediate layer on CoZrNb SUL and minimized its thickness As a result we obtained CoPt nanodot arrays with 150-nm diameter 300-nm pitches and 20-nm heights which have uniform structures on the substrates with the construction of Cu (1-2 nm)/CoZrNb (100 nm)/Cr (5 nm)/glass disk The perpendicular coercivity of the CoPt nanodot arrays was as high as 5 4 kOe From these results we showed that the Cu intermediate layer with even 1-2 nm thick considerably improved the deposition condition on the substrates with CoZrNb SUL to successfully fabricate CoPt nanodot arrays with the diameter and pitches of 80 nm and 160 nm with sufficient uniformity (C) 2010 Elsevier Ltd All rights reserved

We investigated fabrication processes of magnetic nanodot arrays for the ultra-high density magnetic recording media by using an electrodeposition A CoZrNb underlayer was sputter-deposited on a glass disk substrate as a soft magnetic underlayer (SUL) Nano-patterns were formed on the substrate by UV-nanoimprint lithography (UV-NIL) and CoPt was electrodeposited into the nano-patterns For obtaining uniform CoPt nanodot arrays with high perpendicular coercivities we applied thin Cu intermediate layer on CoZrNb SUL and minimized its thickness As a result we obtained CoPt nanodot arrays with 150-nm diameter 300-nm pitches and 20-nm heights which have uniform structures on the substrates with the construction of Cu (1-2 nm)/CoZrNb (100 nm)/Cr (5 nm)/glass disk The perpendicular coercivity of the CoPt nanodot arrays was as high as 5 4 kOe From these results we showed that the Cu intermediate layer with even 1-2 nm thick considerably improved the deposition condition on the substrates with CoZrNb SUL to successfully fabricate CoPt nanodot arrays with the diameter and pitches of 80 nm and 160 nm with sufficient uniformity (C) 2010 Elsevier Ltd All rights reserved

An approach to control the diameter of high-aspect-ratio pores formed into a silicon wafer by an electrochemical etching process is reported. Hole (h(+)) was involved in the etching reaction and the collection of the h(+) was the key factor. Artificial micro-cavities were fabricated on the silicon surface prior to the etching. The depth of the space charge region (SCR), Schottky barrier on the silicon-electrolyte interface, was adjusted regarding the depth of the micro-cavities by applied overpotential and specific resistance of the silicon wafer. The collection of h at the tip of the cavity site was widely controlled by the adjusted SCR. Consequently the electrochemically etched domain at the cavity site was actively tuned, and then high-aspect-ratio pore with the controlled diameter was formed. The diameter was tuned by the SCR depth which was controlled by the overpotential and the specific resistance. The diameter tuning mechanism worked under the mask-free condition. (C) 2010 Elsevier B.V. All rights reserved.

Discrete track media (DTM) and bit-patterned media (BPM) are being extensively studied as routes to achieve higher density hard disk drives. In the DTM and BPM, it is essential to isolate the data tracks or bits with non-magnetic materials to reduce the magnetic noise from adjacent tracks or bits. In contrast to the conventional procedure of physically etching the media, we attempted to isolate the tracks or bits with soft regions using an area-selective ion irradiation method. We prepared hard and soft nano-composite structures by nanoimprinting, followed by ion irradiation. In this study, we confirmed the magnetic reversal process of the hard and soft regions of the nano-composite structure using magnetic force microscopy (MFM) with various external applied magnetic fields. The analysis of the magnetization reversal process of patterned Coupled Granular Continuous (CGC) films with weak exchange coupling confirmed the validity of this novel approach for the fabrication of DTM and BPM.

Synchrotron radiation-induced total reflection X-ray fluorescence (SR-TXRF) analysis is a high sensitive analytical technique that offers limits of detection in the femtogram range for most elements. Besides the analytical aspect, SR-TXRF is mainly used in combination with angle-dependent measurements and/or X-ray absorption near-edge structure (XANES) spectroscopy to gain additional information about the investigated sample. In this article, we briefly discuss the fundamentals of SR-TXRF and follow with several examples of recent research applying the above-mentioned combination of techniques to analytical problems arising from industrial applications and environmental research. (C) 2010 Elsevier Ltd. All rights reserved.

An approach to control the diameter of high-aspect-ratio pores formed into a silicon wafer by an electrochemical etching process is reported. Hole (h(+)) was involved in the etching reaction and the collection of the h(+) was the key factor. Artificial micro-cavities were fabricated on the silicon surface prior to the etching. The depth of the space charge region (SCR), Schottky barrier on the silicon-electrolyte interface, was adjusted regarding the depth of the micro-cavities by applied overpotential and specific resistance of the silicon wafer. The collection of h at the tip of the cavity site was widely controlled by the adjusted SCR. Consequently the electrochemically etched domain at the cavity site was actively tuned, and then high-aspect-ratio pore with the controlled diameter was formed. The diameter was tuned by the SCR depth which was controlled by the overpotential and the specific resistance. The diameter tuning mechanism worked under the mask-free condition. (C) 2010 Elsevier B.V. All rights reserved.

This paper describes the fabrication process of CoPt nandot arrays on a glass disk substrate with a CoZrNb underlayer as a soft magnetic underlayer (SUL) by using an electrochemical process, and also the analysis on the magnetic properties of these fabricated CoPt nanodot arrays. We formed nano-patterned substrates by UV-nanoimprint lithography (UV-NIL) on the glass disk substrate. CoPt was electrodeposited into the nano-patterned substrates optimizing the electrodeposition condition and bath composition as well as a Cu intermediate layer. The construction of the nanodot arrays were CoPt nanodot arrays (20 nm)/Cu (5 nm)/CoZrNb (100 nm)/Cr (5 nm)/Glass disk. Magnetic signals were clearly observed on the dc magnetized state and multi domain were observed in each nanodot on the ac magnetized state by magnetic force microscopy (MFM). The perpendicular coercivity of the CoPt nanodot arrays was 430 kA/m. These results showed electrochemical process can be used for the manufacture of magnetic recording media.

The electrochemical behavior of Al-Si alloy films in zincate solution was investigated to elucidate the effects of zincate pretreatment on the Zn morphology and subsequent electroless NiP deposition, which is used for under bump metallization (UBM) in integrated circuit (IC) chip packaging. To investigate the electrochemical behavior of the Al-Si films during the zincate pretreatment, the immersion potential and the surface morphology during Zn and NiP deposition were evaluated using Al-Si electrodes that had been fabricated onto two types of Si substrates with different specific resistances. A heterogeneous point was observed for samples fabricated onto Si substrates with high specific resistance (45-95 Ωm), but no such point was observed on samples fabricated onto Si substrates with low specific resistance (0.00001-0.00002 Ωm). This result suggests that the morphology of the deposits was affected considerably by the specific resistance of the Si substrate.

Copper electrolysis is carried out in a stagnant 0.05 M CuSO4 aqueous electrolyte under alternating current (AC) condition. Transient mass transfer rate of Cu2+ ion caused by copper electrodeposition with AC is studied theoretically and experimentally with the holographic interferometer. The effect of buoyancy convection developing along the vertical plane electrodes on the transient concentration boundary layer (CBL) structure accompanying with AC is focused on. Two different electrode configurations, the horizontal cathode over anode and the vertical electrode settings, are employed for this purpose. The CBL thickness tends to increase over long duration time in the former configuration, while it converges to a steady-state value in the latter. Both calculated and measured concentration profiles in the vertical electrode configuration exhibit the characteristic transient behaviors composed of the pulsating CBL (PCBL) in the vicinity of the cathode surface and the stationary CBL (SCBL) outside the PCBL The appearance of the SCBL is ascribed to mass transfer by advection, and the overall CBL thickness depends on the hydrodynamic conditions such as the magnitude of buoyancy convection. (C) 2010 Elsevier Ltd. All rights reserved.

To increase the areal density of hard disk drives (HDDs), discrete track media (DTM) and bit-patterned media (BPM) are being extensively studied. In the DTM and BPM, it is essential to isolate data tracks or bits. Unlike isolating the data tracks or bits using the conventional procedure involving physical etching, we attempted to isolate the tracks or bits with a soft guard band using an area-selective ion irradiation method. We prepared hard and soft (H/S) patterned films by nanoimprinting followed by ion irradiation. We confirmed the magnetic isolation of tracks and bits using magnetic force microscopy (MFM) images and magnetooptical Kerr effect (MOKE) signals. The results of an analysis of the magnetic properties of patterned coupled granular continuous (CGC) films with weak exchange coupling confirmed the validity of this novel approach for the fabrication of DTM and BPM.

We attempted to fabricate patterned media using the electrochemical deposition process along with nanopatterned substrates prepared by the electron beam lithography (EBL), UV nanoimprint lithography (UV-NIL), and spin-on-glass nanoimprint lithography (SOG-NIL) approaches. CoPt was electrodeposited into the nanopatterned substrates and chemical mechanical polishing was carried out to planarize the surface. It was clarified that CoPt nanodot arrays were successfully deposited into the patterned nanopores fabricated by UV-NIL and SOG-NIL as well as by EBL with high area selectivity and uniformity. The density of the CoPt nanodot arrays deposited into the nanopores fabricated by EBL was equal up to an areal recording density of 250 Gbit/in(2). (C) 2008 Elsevier B. V. All rights reserved.

We present fabrication methods of functional three-dimensional (3-D) micromesh structures coated with titanium dioxide (TiO(2)) microparticles and biocatalysts. The 3-D micromesh structures are useful for fabricating highly efficient microreactors because of their large surface area. In this study, TiO(2)-embedded SU-8 micromesh structures were formed by coating a TiO(2)/SU-8 mixture onto the surface of SU-8 micromesh structures. Biocatalyst-immobilized micromesh structures were also formed by coating a biocatalyst/photopolymer mixture onto SU-8 micromesh structures.

Microreactors and micro-fluidic devices require micro-tube structures to reserve and manipulate extremely small volume of liquid specimen, and nano-hole on the micro-tube is useful for its injection, aspiration and filtration, etc. In the present study, we attempted to develop a precise etching process to form nano-hole to the edge part of the micro glass tube by controlling SiO2 etching conditions with diluted aqueous HF solution. The arrayed micro-glass-tubes were fabricated by electrochemical etching of Si wafer followed by wet-thermal oxidation. The bottoms of arrayed micro-glass-tubes were exposed from Si wafer, which possessed pyramid-shape edges. The etching with optimized concentration of HF formed uniform nano-holes only at every bottom edge, indicating self-alignment of the etching process. The diameter of the nano-holes was controllable in the range of ca. 100-500 nm by adjusting the immersion duration and thickness of the glass tube. Nonlinear diffusion of fluoride species to the bottom edges could be the origin of the self-aligned formation of nano-holes at the bottom edges. (C) 2007 Elsevier Ltd. All rights reserved.

Nanoscale dot patterns of cobalt alloy were formed on a silicon substrate using the ultra-violet nanoimprint lithography (UV-NIL) technology in combination with an electrodeposition process. We developed an improved UV-NIL equipment that can evacuate the chamber during imprinting. Using this equipment, we successfully imprinted 240-nm dot patterns with 500 nm pitch on a photocurable resin with high dimensional accuracy. Thickness control of the resin and imprinting under vacuum are important issues to obtain fine nanopatterns. Using these resin patterns as a mask layer, 300-nm cobalt alloy patterns are successfully formed by the electrodeposition process. (c) 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

The oxidation mechanism of hydrazine and hydroxylamine were investigated using molecular orbital (MO) calculation. Two pathways for their reactions were verified. One is initiated by hydrogen elimination from the reducing agent, followed by coordination of hydroxyl group to center nitrogen atom accompanied with electron emission. Another is initiated by coordination of hydroxyl group to hydrogen atom to form H2O, which is eliminated later, followed by electron emission. The calculated results indicated that the oxidation reactions of hydrazine preferentially proceeded via the second pathway. It was also indicated that only the first electron emission steps of the hydrazine oxidation took place on Cu surface, while the following reactions proceeded at near the solid/liquid interface. The oxidation of hydroxylamine also proceeded via the elimination reaction of H2O. After the oxidation, calculated heats of reactions suggested that OH radical, generated from N2O as a product, decomposed hydroxylamine.

The covalent attachment of alkyl groups to silicon surfaces, via carbon-silicon bond formation, has been attempted using gas-surface reactions starting from Cl-terminated Si(111) or H:Si(111) under ultraviolet light irradiation. The formation of Cl-terminated Si(111) and its resulting stability were examined prior to deposition of organic molecules. High-resolution electron energy loss spectroscopy (HREELS) was utilized for detecting surface-bound adsorbates. The detection of photo-deposited organic species on CI:Si(111) from gas-phase CH4 or CH2=CH2 was not significant. On H:Si(111), it was evident that after the photoreaction with gas-phase C2H5Cl, C2H5 groups were chemically bonded to the surface Si atoms through single covalent bonds. The C2H5 groups were thermally stable at temperatures below 600 K. Alkyl monolayers prepared on silicon surfaces by dry process will lead to a new prospective technology of nanoscale fabrication and biochemical applications. (c) 2006 Elsevier B.V. All rights reserved.

We succeeded in fabricating 256-pixel arrays of Ti/Au transition edge sensor (TES) microcalorimeters with electrodeposited microabsorbers made of Bi, and report on their test results. We confirmed till pixels tested so far were alive, however most of the microabsorbers were stripped off during cooling cycles. We investigated some pixels by irradiating with 5.9 keV X-rays, and confirmed that they actually worked as microcalorimeters. The X-ray pulses are represented by a sum of two components with different decay times. The ratio of the two components fluctuates from pulse to pulse, which limits the energy resolution to similar to 200 eV. We discuss the pulse shape of two decay-time components considering thermal conductivities, i.e., inside microabsorbers, between microabsorbers and TES. (c) 2005 Elsevier B.V. All rights reserved.

The oxidation mechanism of aldehydes, which are commonly used as reductants for an electroless deposition process, was studied by using Density Functional Theory (DFT) calculations. The reaction pathway of the three aldehydes, i.e., formaldehyde, acetaldehyde and glyoxylic acid, with different functional groups, were examined by calculating energy profiles of all intermediate species. It was indicated that the pathway in an isolated system proceeds via dianion-free intermediate species. Taking the solvation effect into consideration, it was indicated that the oxidation reactions of the three aldehydes preferably proceed at the solid/liquid interface. In combination with a Cu metal cluster as a model of metal surface, it was also indicated that the oxidation reactions proceed preferentially at the Cu surface. It was expected that the adsorption/desorption energy at the Cu surface of glyoxylic acid, which has an electron-accepting carboxyl group, was smaller and substituent effect lead to its high reducibility. (C) 2005 Elsevier Ltd. All rights reserved.

Maskless and electroless fabrication was demonstrated to form patterned nanostructures of various metal species, based upon the process previously developed by the authors. In this process, the metallic nanostructures were formed on the surface of clean, hydrogen terminated p-(1 0 0) Si wafer with pre-patterned nanoscopic defects, which were confirmed to possess higher activity for the reductive deposition reaction of the metal ion species. The deposition was achieved spontaneously and selectively at the defect sites on the wafer surface by immersing into dilute aqueous fluoride solution containing trace amount of metal ion species. By optimizing the formation condition of the patterned defects and composition of the solution, fabrication of patterned nanostructures of various metallic species such as Au, Ag, and Co, was achieved. Formation of the patterned nanostructures to 10 mu m(2) in extent, as well as control of the feature size of the deposits by adjusting the formation condition of the pattemed defects were also attempted. (C) 2005 Elsevier Ltd. All rights reserved.

Electrochemical behavior of At and At alloy films in zincate solution was investigated to elucidate the effect of the zincate pretreatment for electroless NiP deposition, which is used for under bump metallization for LSI interconnects. The immersion potential for AlCu and AlSiCu, immediately reached to constant, which was almost equal potential to zinc reference electrode. The corrosion current for the AlCu and AlSiCu films was larger than that of the At and AlSi films in the zincate solution. It was also confirmed that the deposited Zn at the surface of AlCu and AlSiCu films possessed smaller grain size and larger amount of nucleation, resulted in the formation of flat NiP films. (C) 2005 Elsevier Ltd. All rights reserved.

Fabrication process for picoliter volume SiO2 glass tube array partially embedded in Si wafer was developed. As a template for the glass tubes, macropore array was formed at the surface of n-Si(1 0 0) wafer by photo-assisted electrochemical etching process. The area-selective formation of the array was achieved by applying Au/Cr micropatterns formed at the back-side surface of the substrate as the shade mask, which controls the illumination condition to optimize the etching reaction conditions. Subsequently, surface of the macropores was wet-thermally oxidized to form glass layer, and the bulk Si region was removed by alkaline etching, remaining the "glass tubes". As a result of complete removal of the bulk Si, released glass tubes were obtained. By partial removal of the bulk Si part, the glass tubes were exposed, fixed in the remaining Si substrate in the form of well-ordered array. It was confirmed that the depth, the exposed region and the wall thickness of each glass tube were controllable by adjusting the parameters such as the duration of the Si electrochemical etching, the alkaline etching and the wet-thermal oxidation, respectively. In order to demonstrate microreaction in the glass tube, aqueous rhodamine B solution was injected into the tubes and excitation light was irradiated to them. As a result, the fluorescence of rhodamine B was clearly detected, confirming the applicability of the glass tubes for various kinds of devices and systems such as microreactors. (C) 2005 Elsevier Ltd. All rights reserved.

To realize highly sensitive electrochemical immunoassays, a micro-fabricated three-dimensional (313) electrode was fabricated and applied to enzyme immuno assay based on production of a redox species. The dimensions of the electrodes are 10 mu m in width and 30 mu m in height, with 20 mu m spacing in between, and the 30 pairs of anode and cathode electrodes made up a single sensor. This structure lead to enhancement of the electrochemical reaction, nearly 100% of trap ratio of redox species. It can be applied to highly sensitive enzyme immuno sensing based on p-aminophenylphosphate (PAPP). Applicability of this technique to the immuno assay for one of the clinical diagnostic marker proteins (alpha-fetoprotein; AFP) from 6 to 500 ng/mL was demonstrated. (c) 2004 Elsevier B.V. All rights reserved.

To realize highly sensitive electrochemical immunoassays, a micro-fabricated three-dimensional (313) electrode was fabricated and applied to enzyme immuno assay based on production of a redox species. The dimensions of the electrodes are 10 mu m in width and 30 mu m in height, with 20 mu m spacing in between, and the 30 pairs of anode and cathode electrodes made up a single sensor. This structure lead to enhancement of the electrochemical reaction, nearly 100% of trap ratio of redox species. It can be applied to highly sensitive enzyme immuno sensing based on p-aminophenylphosphate (PAPP). Applicability of this technique to the immuno assay for one of the clinical diagnostic marker proteins (alpha-fetoprotein; AFP) from 6 to 500 ng/mL was demonstrated. (c) 2004 Elsevier B.V. All rights reserved.

Array of macropores filled with electrodeposited Ni was formed on Si substrate applying the novel process, which consists of Si electrochemical etching and Ni electrodeposition using single electrolyte. This electrolyte contained HF as Si dissolution agent and Ni(OSO2NH2)(2) 4H(2)O as Ni2+ source for Ni electrodeposition. First, array of macropores was formed on Si (100) substrate by applying anodic current. The formation was carried out area-selectively by applying Au/Cr micropatterns formed at the back side surface of the substrate as the shade mask, which enables to control the illumination condition for hole generation condition. Subsequently, the applied bias was switched to cathodic current, and Ni was filled into c.a. 200 mu m depth Si macropores without void-like defects. Array of Ni needles with smooth surface was formed area-selectively by removal of the Si region of the Ni filled specimen with 25 wt% tetramethylammonium hydroxide (TMAH) aqueous solution at 90 degrees C.

Array of macropores filled with electrodeposited Ni was formed on Si substrate applying the novel process, which consists of Si electrochemical etching and Ni electrodeposition using single electrolyte. This electrolyte contained HF as Si dissolution agent and Ni(OSO2NH2)(2) 4H(2)O as Ni2+ source for Ni electrodeposition. First, array of macropores was formed on Si (100) substrate by applying anodic current. The formation was carried out area-selectively by applying Au/Cr micropatterns formed at the back side surface of the substrate as the shade mask, which enables to control the illumination condition for hole generation condition. Subsequently, the applied bias was switched to cathodic current, and Ni was filled into c.a. 200 mu m depth Si macropores without void-like defects. Array of Ni needles with smooth surface was formed area-selectively by removal of the Si region of the Ni filled specimen with 25 wt% tetramethylammonium hydroxide (TMAH) aqueous solution at 90 degrees C.

Effects of the Pd seeds formed by an electrochemical process on the microstructures of Co/Pd multilayered perpendicular recording media were investigated. By immersing a CoZrNb soft magnetic underlayer (SUL) into PdCl2 aqueous solution, island-like Pd clusters were deposited on the SUL, resulting from the electrochemical substitution reaction. Transmission electron microscopic observations revealed that the columnar Co/Pd multilayered grains with clear boundaries grew on the SUL with the Pd clusters. The clear grain boundaries, where the densities of Co and Pd elements were low, were thought to cause the magnetic exchange decoupling between the Co/Pd grains, leading to an increase of perpendicular coercivity and a decrease of magnetic cluster size of Co/Pd multilayered film. Consequently, lower medium noise was obtained for the Co/Pd multilayered medium with the Pd clusters than for that with a sputter-deposited Pd seedlayer. From these investigations, it was clarified that the SUL surface with Pd clusters provided the effective nucleation sites for a well-defined Co/Pd multilayered grain growth. (C) 2004 Elsevier B.V. All rights reserved.

Effects of the Pd seeds formed by an electrochemical process on the microstructures of Co/Pd multilayered perpendicular recording media were investigated. By immersing a CoZrNb soft magnetic underlayer (SUL) into PdCl2 aqueous solution, island-like Pd clusters were deposited on the SUL, resulting from the electrochemical substitution reaction. Transmission electron microscopic observations revealed that the columnar Co/Pd multilayered grains with clear boundaries grew on the SUL with the Pd clusters. The clear grain boundaries, where the densities of Co and Pd elements were low, were thought to cause the magnetic exchange decoupling between the Co/Pd grains, leading to an increase of perpendicular coercivity and a decrease of magnetic cluster size of Co/Pd multilayered film. Consequently, lower medium noise was obtained for the Co/Pd multilayered medium with the Pd clusters than for that with a sputter-deposited Pd seedlayer. From these investigations, it was clarified that the SUL surface with Pd clusters provided the effective nucleation sites for a well-defined Co/Pd multilayered grain growth. (C) 2004 Elsevier B.V. All rights reserved.

Electroless deposition process for fabricating magnetic dot arrays was studied. A patterned Si substrate with a SiO2 resist was produced by processes combined with electron-beam lithography and reactive ion etching. By immersing the patterned Si substrate into a CoNiP electroless deposition bath, CoNiP was deposited only into the patterned pores, demonstrating a satisfactory area selectivity of the deposition. Excellent uniformity on the CoNiP deposition into the patterned pores with diameter less than 100 nm and high aspect ratio (&gt; 5) was achieved by applying chemical activation processes using a Pd solution prior to the deposition. The CoNiP dot arrays exhibited higher perpendicular squareness ratio than that of CoNiP continuous film and showed a clear magnetization state at DC-magnetized state, which originated from the shape anisotropy caused by high aspect ratio of the dot patterns. (C) 2004 Elsevier B.V. All rights reserved.

Pd cluster seeds for a double-layered perpendicular magnetic recording medium composed of a Co/Pd multilayered film and a CoZrNb soft magnetic underlayer (SUL) were fabricated with an electrochemical treatment. By immersing the SUL into an aqueous PdCl2 solution, the substitution of Pd for Co at the surface of the SUL took place, which was caused by the difference in electrochemical redox potential between Pd and Co. Uniformly distributed Pd clusters with 8 nm in diameter were successfully formed with the treatment for the optimized duration. Use of the Pd clusters as the seeds for deposition of the Co/Pd multilayered film increased the perpendicular coercivity and reduced the size of magnetic cluster of the film. These results suggested that the Pd cluster seeds led to the formation of magnetically isolated Co/Pd multilayered grains, improving the magnetic properties of Co/Pd multilayered film.

Microscale Bi electrodeposition process was developed to fabricate the array of mushroom-shaped absorbers for the high sensitive X-ray imaging sensor, so called X-ray microcalorimeter array. The bath composition and operating conditions for Bi electrodeposition was optimized, and sufficient bath stability and surface smoothness of the deposits were achieved by applying the additives such as diethylenetriamine pentaacetic acid and sodium n-dodecyl sulfate with appropriate concentration. By applying the two-step exposure steps for the "stem" part and the "roof" part, the mold to deposit the mushroom-shaped microstructure was formed from single-layered photoresist coating. The absorber array was successfully fabricated by the sequential processes of Bi electrodeposition into the mold, precise polishing, and mold removal.

The oxidation mechanism of TiCl3 as a reductant for an electroless deposition process was studied by ab initio molecular orbital method. The reaction process of TiCl3 proceeds with the substitution of Cl- to OH-. Net charge and spin density of the reactant, product, and intermediates were evaluated. It was suggested that the electron emission of TiCl3, which is originated by the oxidation of Ti(III) to Ti(IV), took place when Cl is replaced by OH- to form Ti(OH)(4). The catalytic activity of the metal surface, which is one of the most important factors for the electroless deposition process, was studied using a Pd-4 Cluster as a model surface. It was suggested that the Pd-4 cluster enhanced the reaction of TiCl3 to emit the electron. The effect of solvation is also taken into account in terms of the dielectric field constant. It was indicated that the heat of oxidation reaction shifted to an exothermic reaction with decreasing dielectric constant, indicating that the reaction preferentially proceeds in the vicinity of solid/liquid interface. However, it was indicated that the reaction could proceed in the bulk solution, suggesting that appropriate stabilization such as formation of complex is required for the application of the TiCl3 to the electroless deposition process.

Microscale Bi electrodeposition process was developed to fabricate the array of mushroom-shaped absorbers for the high sensitive X-ray imaging sensor, so called X-ray microcalorimeter array. The bath composition and operating conditions for Bi electrodeposition was optimized, and sufficient bath stability and surface smoothness of the deposits were achieved by applying the additives such as diethylenetriamine pentaacetic acid and sodium n-dodecyl sulfate with appropriate concentration. By applying the two-step exposure steps for the "stem" part and the "roof" part, the mold to deposit the mushroom-shaped microstructure was formed from single-layered photoresist coating. The absorber array was successfully fabricated by the sequential processes of Bi electrodeposition into the mold, precise polishing, and mold removal.

Performance of microcalorimeters with a Ti/Au transition-edge sensor (TES) and an electrodeposited absorber has been investigated. The absorbers are in a mushroom-shape made of Sn or Bi. With an Sn absorber we observed a long time scale component of 1.8 ms for X-ray pulses, which is due presumably to recombination of quasiparticles into phonons. As a result, the energy resolution is not good with the Sn absorber. Better energy resolution of 28 +/- 1 eV was obtained with an incomplete-shaped Bi absorber, although the long component was also seen with smaller level. A calorimeter with only a neck of the An seed layer for the electrodeposition had the best energy resolution of 6.3 +/- 0.4 eV in spite of saturated pulses and relatively high transition temperature of 210 mK. (C) 2003 Elsevier B.V. All rights reserved.

We have developed multi-pixel TES microcalorimeters in order to realize high-energy resolution and X-ray imaging. A Sn absorber and a Bi absorber were formed on Si3N4 and SiO2 membrane using two-step exposure photolithography and electrodeposition. A FEM analysis was carried out to investigate the performance of the X-ray microabsorbers. In addition, a superconducting through-wafer interconnection was demonstrated considering the future X-ray imager using microcalorimeters. Detail of the fabrication techniques, characteristics and simulation results of two types of the microabsorbers, as well as those of the calorimeters are described. (C) 2003 Elsevier B.V. All rights reserved.

We are developing a Ti/Au TES microcalorimeter array for future Japanese X-ray astronomy missions. The goal is an energy resolution of 2-5 eV at 6 keV, and an array of 100-1000 pixels to achieve a geometrical area of &gt;1 cm(2) and a moderate spatial resolution simultaneously. The energy resolution was improved to similar to6 eV at 6 keV with a very fast time constant (&lt;100 mus). To achieve a high coverage fraction, it is necessary to fabricate mushroom-shaped X-ray microabsorbers. We are developing an electrodeposition fabrication technique that is suitable for our process. Sn was used as absorber material, but the energy resolution was not good due to the existence of long-lived quasiparticles. Bi is also used, and the process is under optimization now. The readout strategy is to multiplex signals in the frequency domain, using a bridge circuit. So far, we succeeded in multiplexing two pixels modulated with 50 and 20 kHz at 440 mK. The energy resolution obtained at 110 mK was 33 eV (25 kHz). (C) 2003 Elsevier B.V. All rights reserved.

Formation of the methyl- and n-butyl monolayer on (Cl)Si(I 11) surfaces by using the Grignard reaction and their electro-chemical behavior was investigated. The modified Si(I 11) surfaces were indicated to be closely packed with a single moiety species. The methyl-modified Si(I 11) surface was composed of (I x 1) adlattice structure. The methyl-modified surface was stable in aqueous solution, and showed essentially good electrical conductive property with p-n junction like behavior.

Performance of microcalorimeters with a Ti/Au transition-edge sensor (TES) and an electrodeposited absorber has been investigated. The absorbers are in a mushroom-shape made of Sn or Bi. With an Sn absorber we observed a long time scale component of 1.8 ms for X-ray pulses, which is due presumably to recombination of quasiparticles into phonons. As a result, the energy resolution is not good with the Sn absorber. Better energy resolution of 28 +/- 1 eV was obtained with an incomplete-shaped Bi absorber, although the long component was also seen with smaller level. A calorimeter with only a neck of the An seed layer for the electrodeposition had the best energy resolution of 6.3 +/- 0.4 eV in spite of saturated pulses and relatively high transition temperature of 210 mK. (C) 2003 Elsevier B.V. All rights reserved.

We have developed multi-pixel TES microcalorimeters in order to realize high-energy resolution and X-ray imaging. A Sn absorber and a Bi absorber were formed on Si3N4 and SiO2 membrane using two-step exposure photolithography and electrodeposition. A FEM analysis was carried out to investigate the performance of the X-ray microabsorbers. In addition, a superconducting through-wafer interconnection was demonstrated considering the future X-ray imager using microcalorimeters. Detail of the fabrication techniques, characteristics and simulation results of two types of the microabsorbers, as well as those of the calorimeters are described. (C) 2003 Elsevier B.V. All rights reserved.

We are developing a Ti/Au TES microcalorimeter array for future Japanese X-ray astronomy missions. The goal is an energy resolution of 2-5 eV at 6 keV, and an array of 100-1000 pixels to achieve a geometrical area of &gt;1 cm(2) and a moderate spatial resolution simultaneously. The energy resolution was improved to similar to6 eV at 6 keV with a very fast time constant (&lt;100 mus). To achieve a high coverage fraction, it is necessary to fabricate mushroom-shaped X-ray microabsorbers. We are developing an electrodeposition fabrication technique that is suitable for our process. Sn was used as absorber material, but the energy resolution was not good due to the existence of long-lived quasiparticles. Bi is also used, and the process is under optimization now. The readout strategy is to multiplex signals in the frequency domain, using a bridge circuit. So far, we succeeded in multiplexing two pixels modulated with 50 and 20 kHz at 440 mK. The energy resolution obtained at 110 mK was 33 eV (25 kHz). (C) 2003 Elsevier B.V. All rights reserved.

Formation of the methyl- and n-butyl monolayer on (Cl)Si(I 11) surfaces by using the Grignard reaction and their electro-chemical behavior was investigated. The modified Si(I 11) surfaces were indicated to be closely packed with a single moiety species. The methyl-modified Si(I 11) surface was composed of (I x 1) adlattice structure. The methyl-modified surface was stable in aqueous solution, and showed essentially good electrical conductive property with p-n junction like behavior.

Formation of organosilane monolayer templates using ultraviolet and electron-beam (EB) lithography was investigated. The oligonucleotides were covalently immobilized with high selectivity only to the amino-monolayer modified regions locally formed on the template surfaces at micro and nanometer scale. By using EB lithography, patterned immobilization in nanometer scale, as small as 20nm, was achieved.

Formation of organosilane monolayer templates using ultraviolet and electron-beam (EB) lithography was investigated. The oligonucleotides were covalently immobilized with high selectivity only to the amino-monolayer modified regions locally formed on the template surfaces at micro and nanometer scale. By using EB lithography, patterned immobilization in nanometer scale, as small as 20nm, was achieved.

Sn electrodeposition was employed for fabricating an array of microabsorbers with a 'mushroom-shaped' microstructure for a precision X-ray microdetector, the so called X-ray microcalorimeter. A deposition process for flat and smooth Sn films, which was suitable for the use of the absorber material, was developed by optimizing the conditions of additives such as o-cresol-4-sulfonic acid and polyethyleneglycol (PEG) to the Sn bath. The Sn films exhibited suitable properties, i.e. a higher superconducting transition temperature than the operating temperature of the X-ray microcalorimeter. The mushroom-shaped absorber array was successfully fabricated by Sn electrodeposition in combination with a photolithographic technique. (C) 2002 Elsevier Science B.V. All rights reserved.

The oxidation mechanism of dimethylamine borane (DMAB), which acts as a reductant in the electroless deposition process, was studied using ab initio molecular orbital approaches such as Hartree-Fock (HF) and second order Møller-Plesset (MP2) calculations. The overall oxidation process of the DMAB was divided into each elementary reaction in which OH- substitutes H one by one and eventually forms B(OH)4-. The oxidation mechanism of DMAB in the isolated state, which was previously proposed by us, was refined using more accurate basis sets, and the effects of solvation and interaction with metal surface sites on the oxidation mechanism were also studied. Taking the solvation effect into consideration using the self-consistent reaction field method with an isodensity polarized continuum model (SCRF-IPCM), the heat of oxidation was transferred to an exothermic reaction with decreasing dielectric constant. This indicated that the reaction preferably proceeds at the solid|liquid interface. Combined with Cu(111) and Pd(111) neutral cluster models as metal surface sites, it was found that the oxidation reaction proceeds preferentially at the metal surface sites. It was also suggested that the catalytic activity of the deposited metal is caused by its electron acceptivity. © 2003 Elsevier Science B.V. All rights reserved.

As is well known, contamination of the silicon surface by trace metal impurities is responsible for detrimental effects in the production of ULSI circuits. An extensive experimental study of the factors influencing the spontaneous metal nucleation from fluoride solutions on Si substrates was undertaken. In acidic media (dilute HF solution) only noble metals can be deposited. The mechanism for the formation of Cu element nuclei was chosen as a model example. The first stage was the appearance of Cu crystals of a nanoscopic scale, observed by AFM microscopy. These nuclei soon induce corrosion pits due to the formation of a short-circuited electrochemical cell. In concentrated NH4F solutions, the open circuit potential (ocp) of Si samples is highly negative and provides an efficient driving force for nucleation even for common metals like Fe. Our results show that the deposition of Fe is hardly observable when Fe only is present, but in the presence of Cu, a catalytic effect is observed leading to the co-deposition of Fe + Cu nuclei. In all cases surface defects on the Si substrate are generated by the corrosion pits. (C) 2002 Elsevier Science B.V. All rights reserved.

Attempt was made to develop novel maskless and electroless fabrication process of metal nanostructures by controlling local surface activity for the deposition reaction at silicon wafer surfaces. P-Si(100) wafers were cleaned to obtain hydrogen-terminated surface and nanoscopic patterns were formed on the surface by nanoindentation technique using a scanning probe microscope (SPM) with a diamond probe. By controlling the parameters such as the indentation force (within the order of 1 - 10 muN), nanoscopic patterns with different degrees of defects were formed. The scanning surface potential microscopy (SPoM) analysis clarified that these sites locally possessed negative shift in potential, i.e., higher activity for the reductive deposition of metal ions, which increased with an increase in the degree of defect. In order to achieve spontaneous (electroless) and selective deposition at those patterns, conditions of the solution were optimized and the formation of metal nanostructures, such as Cu nanodot arrays and wires, has been achieved. Capability of the present process to form nanostructures whose feature size is as small as 50 nm was demonstrated. (C) 2003 Elsevier Ltd. All rights reserved.

Signal and noise characteristics of Co/Pd multilayer perpendicular magnetic recording media are discussed based upon MFM analysis. The noise of the Co/Pd multilayer media is originated mainly from irregularities in the magnetic transition regions, and can be drastically suppressed by increasing the thickness of the carbon underlayer although a large number of reversed magnetic domains between the magnetic transitions still exist. The fine magnetic clusters formed in the medium with a thick carbon underlayer result in clear magnetic transition boundaries of recorded bits in the high recording density region. By examining the profile of the M-H loops. the decrement in the x value, which is defined as the slope of M-H loop at the value of coercivity, improves the signal to noise (S/N) ratio for the Co/Pd multilayer media. (C) 2001 Elsevier Science B.V. All rights reserved.

Molecular orbital study was applied to investigate electroless deposition processes, focusing upon reducibility of reductants as well as the effect of catalytic activity of the metal surfaces. Elementary reaction pathways of the reductants such as dimethylamine borane, hypophosphite ion, formaldehyde, and titanium trichloride were quantitatively examined in terms of the heat of reaction. It was indicated that the reaction via 5-coordinate intermediates was favorable for these species and that the value could be used for quantitative evaluation of the reducibility of the reductant species. The analysis of solvation effect on the reactions suggested that the reactions preferably proceed at the interfacial region, i.e. the surface of the metal, rather than in the 'bulk' solution region. The effect of catalytic activity of metal surfaces was investigated using a cluster-model surface. It was suggested that the elementary reactions were stabilized on the metal surfaces to enhance the electron emission from the reductants. On the other hand, difference in the stabilization effects for the reaction of hypophosphite ion was obtained due to the variation in the metal species, it was expected that the copper surface is not catalytically active for the reaction, which corresponds to the experimentally known results. (C) 2001 Elsevier Science Ltd. All rights reserved.

The effect of amorphous carbon underlayers on magnetic properties and read-write characteristics of Co73Cr18Pt6Ta3 single layer and Co/Pd multilayer perpendicular magnetic recording media were investigated. The increase in H-c and decrease in alpha, defined as 4 pi (dM/dH)(H=Hc), were observed by increasing the underlayer thickness for both Co-73 Cr18Pt6Ta3 and Co/Pd media. The media with a low alpha value, suggesting a decrease in the exchange coupling, exhibited the higher coercivity and the improvement of S/N ratio. In read-write experiments, the improvement of S/N ratio for the Co/Pd media was achieved up to 400 kFRPI or even higher in the recording density by increasing carbon underlayer thickness, while that for the Co73Cr18Pt6Ta3 media was obtained up to ca. 250 kFRPI.

In order to clarify the origin of the graded magnetic properties by the substrate rotational speed for electroless CoNiP films, electrochemical characteristics such as mixed potential and polarization behaviors were investigated. The results of mixed potential analysis revealed that the cathodic and anodic partial reactions in this system were diffusion- and reaction-controlled stale, respectively. It was shown that the mixed potential of the CoNiP deposition with the substrate rotational speed was dominated mainly by the deposition reaction of Co. The results of the polarization curves for each metal ion clarified that the Co deposition is in the diffusion-controlled state, whereas such a tendency did not appear for the deposition of Ni. This suggests that such a difference in deposition behaviors between Co and Ni with respect to the rotational speed of the substrate results in the formation of graded film properties. (C) 2000 The Electrochemical Society. S0013-4651(00)02-081-4. All rights reserved.

The substrate (Ni)-catalyzed electroless gold plating process invented by Iacovangelo and Zarnoch has been investigated for plating gold on electroless nickel substrates for application to bonding of electronic devices. The process was found to yield uniform and adherent gold films on Ni-B substrates, whereas on Ni-P substrates acceptable gold films were obtained only when the P content was low and a pretreatment procedure was introduced to prevent the formation of surface oxide or to remove it completely. Unlike the conventional galvanic displacement process, the substrate-catalyzed process does not attack the nickel substrates and yields gold films with a very low porosity. Compared with autocatalytic electroless gold plating baths, the substrate-catalyzed bath is inherently more stable, although the maximum gold thickness obtainable is naturally limited. Results of these evaluations are presented in detail. (C) 2000 The Electrochemical Society. S0013-4651(99)106-062-0. All rights reserved.

Gradient control of magnetic properties in electroless-deposited CoNiP films was attempted and microstructural origin of the graded properties was investigated. Control of the single and dual gradient in magnetic properties, such as coercivity, Hc, in the direction of the film thickness was achieved by controlling the rotational speed of substrates during the deposition. The results of cross-sectional scanning electron microscopy and transmission electron microscopy investigations clarified that the size of the crystallites changed according to the speed of the rotation, forming the `graded' microstructure in the film thickness direction, which resulted in the graded properties.

Gradient control of magnetic properties in electroless-deposited CoNiP films was attempted and microstructural origin of the graded properties ties was investigated. Control of the single and dual gradient in magnetic properties, such as coercivity, Hc, in the direction of the film thickness was achieved by controlling the rotational speed or substrates during the deposition. The results of cross-sectional scanning electron microscopy and transmission electron microscopy investigations clarified that the size of the crystalites changed according to the speed of the rotation, forming the "graded" microstructure in the film thickness direction, which resulted in the graded properties. (C) 2000 The Electrochemical Society. All rights reserved.

The mechanism of direct copper plating on nonconductive resin substrates was studied using high-resolution TEM, SEM and XPS. Substrates were catalyzed by Pd/Sn catalyst and subsequently immersed in alkaline solution containing either copper ions or sulfide ions before electroplating. After conversion in the alkaline solution containing copper ions, catalyst colloid particles formed clusters and crystallinity improved. Sulfide compounds, however, formed by conversion in alkaline solution containing sulfide ions. Both conversion techniques markedly promoted propagation in electroplating. The effect is explained by propagation in which improved palladium colloid crystallinity and palladium sulfide formed in conversion play a critical role in determining the propagation rate.

The read-write characteristics of a perpendicular/longitudinal composite medium prepared by sputtering were investigated. The composite medium exhibited a higher voltage than a perpendicular single-layered medium, although the noise of these media was almost the same. The noise of the composite medium increased slightly with the recording density, suggesting that it was affected by the longitudinal underlayer. However, the noise reduction effect of the composite medium was observed by comparing with the simple superposition of the noise of each single layered medium. As a result, it was found that the perpendicular/longitudinal composite medium exhibited a higher S/N value than the perpendicular single-layered medium.

The initial nucleation process of trace amounts of copper metal on the H-Si(111)(1 x 1) surface in aqueous fluoride solution was investigated by ex-situ scanning tunneling microscopy. We observed that copper nucleates preferentially along step edges and appears to inhibit the step-flow etching of silicon. The presence of copper species in the fluoride solution also appears to inhibit the formation of terrace etch pits, which are known to be initiated by dissolved oxygen. It is suggested that silicon-dihydroxyl-cuprous ion complexes are formed at dihydroxyl kink sites, resulting in the preferential nucleation of Cu metal at step edges and the inhibition of step-flow etching. Copper ions in solution may act as catalysts for the disproportionation and electrocatalytic reduction of superoxide anion radical formed by the electrochemical reduction of dissolved oxygen at the silicon surface. Such reactions would reduce the rate of etch-pit initiation and may also decrease the rate of deposition of metallic copper on the silicon surface.

The initial nucleation process of trace amounts of copper metal on the H-Si(111)(1 x 1) surface in aqueous fluoride solution was investigated by ex-situ scanning tunneling microscopy. We observed that copper nucleates preferentially along step edges and appears to inhibit the step-flow etching of silicon. The presence of copper species in the fluoride solution also appears to inhibit the formation of terrace etch pits, which are known to be initiated by dissolved oxygen. It is suggested that silicon-dihydroxyl-cuprous ion complexes are formed at dihydroxyl kink sites, resulting in the preferential nucleation of Cu metal at step edges and the inhibition of step-flow etching. Copper ions in solution may act as catalysts for the disproportionation and electrocatalytic reduction of superoxide anion radical formed by the electrochemical reduction of dissolved oxygen at the silicon surface. Such reactions would reduce the rate of etch-pit initiation and may also decrease the rate of deposition of metallic copper on the silicon surface.

In order to establish the methodology for the preparation of the magnetic recording medium whose properties graded along the head field distribution, an intentional gradient control of coercivity, He, in electroless-deposited CoNiP thin films was attempted. Microstructure and He of the films changed significantly with the rotational speed of the substrate during deposition. Based upon these results, the gradient control of He was achieved by employing a programmed variation of the rotational speed of the substrate during the deposition. It was confirmed that not only "single-gradient" but also "dual-gradient" control of He in the direction of film thickness can be realized. This method is expected to be a useful technique for preparing a recording medium with magnetic properties most suitable for recording system parameters such as head properties.

The growth process of electroless nickel-phosphorous (NiP) films on nonconducting substrate was investigated quantitatively using tapping mode atomic force microscopy (TMAFM) with focus upon the nucleation density on the substrate surface. Three kinds of catalyzing processes were used for polyimide substrates to obtain nucleation densities of 900, 750, and 550 nuclei/mu m(2). The TMAFM observation showed that the film growth proceeds mainly through successive nucleation of fine ''particles'' with several nanometers in diameter and their three-dimensional growth, and that the nucleation density influences the state of aggregation of the particles and hence the resulting surface topography The lower nucleation density developed the rougher surface with larger ''grains'' with a diameter of ca. 80 nm. However, the effect of nucleation density decayed with film growth and eventually vanished at a thickness of ca. 2000 nm due to successive nucleation. For comparison, the growth process of NiP on NiP coated Al substrate, which is used for rigid magnetic disk applications and has a higher nucleation density of 3000 nuclei/mu m(2), was also examined. This process resulted in a smooth surface without the formation of ''aggregates.'' Bated upon these results, the root-mean-square roughness and scaling analyses were performed to evaluate quantitatively the differences in growth process.

A compositionally inhomogeneous state in electroless-deposited CoNiP films with perpendicular magnetic anisotropy is investigated using spin-echo 59Co nuclear magnetic resonance (NMR), focusing on its correlation with magnetic properties. By adjusting pH of the electroless-deposition bath, films were prepared which possess almost the same average composition (Co42Ni50P8) and crystal orientation, but the differing values of coercivity (Hc). By analyzing the shift in peak resonance frequency of NMR spectra of the CoNiP films with respect to that of bulk CoNi alloys, we observed the formation of a compositionally inhomogeneous state in the film which possesses high Hc of 2600 Oe, whereas formation of inhomogeneities was not observed for the low-Hc films. By assuming that a Co-enriched ferromagnetic component detected by NMR was separated from a non-magnetic amorphous Ni-P component, we found that the high-Hc film consists of Co42Ni26 and Ni24P8. Moreover, the results of high spatial resolution X-ray microanalysis on the high-Hc film showed a tendency that the Co-enriched ferromagnetic component segregates to the center of grains and the Ni-P non-magnetic component segregates to grain boundaries. Such evidence indicates that compositional inhomogeneities could be one of the origins of high-Hc in CoNiP films.

The possibility of electrodeposition of soft gold from a thiosulfate-sulfite bath was explored for electronics applications. The bath does not contain cyanide, and it is operated at a near neutral pH and a mildly elevated temperature. The bath is stable, does not undergo spontaneous decomposition without the addition of any stabilizer, and yields gold deposits with a hardness sufficiently low for use as gold bumps on semiconductor devices. Factors affecting the hardness were investigated in detail. It is shown that the use of high concentrations of the complexing agents and/or the addition of thallium(I) ions decreases both hardness and sulfur content of the deposit. The lowest Vickers hardness values achieved were approximately 80 kg mm(-2) in the as-deposited state and 50 kg mm(-2) after annealing at 350 degrees C for 30 min in air. The relationship between hardness and microstructure of the deposit was also examined.

A compositionally inhomogeneous state in electroless-deposited CoNiP films with perpendicular magnetic anisotropy is investigated using spin-echo 59Co nuclear magnetic resonance (NMR), focusing on its correlation with magnetic properties. By adjusting pH of the electroless-deposition bath, films were prepared which possess almost the same average composition (Co42Ni50P8) and crystal orientation, but the differing values of coercivity (Hc). By analyzing the shift in peak resonance frequency of NMR spectra of the CoNiP films with respect to that of bulk CoNi alloys, we observed the formation of a compositionally inhomogeneous state in the film which possesses high Hc of 2600 Oe, whereas formation of inhomogeneities was not observed for the low-Hc films. By assuming that a Co-enriched ferromagnetic component detected by NMR was separated from a non-magnetic amorphous Ni-P component, we found that the high-Hc film consists of Co42Ni26 and Ni24P8. Moreover, the results of high spatial resolution X-ray microanalysis on the high-Hc film showed a tendency that the Co-enriched ferromagnetic component segregates to the center of grains and the Ni-P non-magnetic component segregates to grain boundaries. Such evidence indicates that compositional inhomogeneities could be one of the origins of high-Hc in CoNiP films.

The recording characteristics of a composite medium with a longitudinal magnetization recording layer as a underlayer of a perpendicular magnetization recording layer were evaluated by using ring-type heads. The results suggest that the residual magnetization mode of the medium is a phase synchronization mode, which forms a horseshoe-shaped magnetization region composed of the strong perpendicular magnetization region of the perpendicular layer and the longitudinal magnetization region of the underlayer. The reproduced voltage of the medium is higher than that obtained by simple superposition of the outputs of the perpendicular top layer and the longitudinal under-layer, and the waveform of the medium shows an almost single-peaked pulse. The recording density response and peak shift characteristics are not restricted by the characteristics of the underlayer. The magnetization state of the medium can be controlled by the medium and head parameters, indicating the importance of optimizing these parameters.

The effects of perpendicular layer thickness on rémanent magnetization states and recording characteristics of perpendicular-longitudinal composite media were investigated. The contribution of perpendicular magnetic reversal is varied due to a change in the thickness of perpendicular layer
the transition length of the thinner perpendicular layer medium was broader than that of thicker perpendicular medium. The medium with thicker perpendicular layer shown better performance not only in recording density response but also peak shift characteristics. In order to realize excellent read/write characteristics, optimization of the thickness of perpendicular layer becomes one of the important factors, in addition to the optimization of the underlayer parameters. © 1996 IEEE.

Effects of additives of Cl^- and glue in the high speed copper electrodeposition on the surface morphology of copper foil to form pyramidal shape were investigated by means of SEM and TEM observation. The surface pyramidal deposition at the copper foil deposited from the standard conditions of 50ppm Cl^- and 2ppm glue is controlled by formation of perpendicular columnar microstructure. The structure became clearer, at the surface region. The additives of Cl^- and glue promoted and suppressed the formation of columnar structure, respectively, the columnar structure formation corresponded well to the &lsaquo;110&rsaquo; direction growth of copper crystals. The complex effect of 50ppmCl^- and 2ppm glue determined the uniformity of surface pyramidal deposition and the shape of pyramid form became shaper with the additive of glue.

The peak shift characteristics of perpendicular-longitudinal composite media in combination with a ring-typehead were investigated. It was found that the composite media had excellent peak shift characteristics in the region where the underlayer-medium showed worse characteristics. In the case of the composite media, strong perpendicular magnetization of the perpendicular recording layer suppressed the unfavorable effect of the underlayer. The underlayer's magnetization had great influence on the peak shift characteristics of the composite media, especially in the higher recording region. It is suggested that the peak shift characteristics are mainly subject to the condition of perpendicular magnetic reversal formed in the composite media.

Effects of saturation flux density (Bs) of read/write head on the recording characteristics of perpendicular/longitudinal composite medium were investigated. It was found that the recording sensitivity was improved by applying the higher Bs head. In higher density region, the reproduced-voltage-enhancement was enlarged with high Bs head, however, at the higher MMF region, the read/write characteristics was worse because the head field penetration becomes broad. Therefore, it was necessary to optimize the medium parameters in account to the head parameter.

The growth morphologies of electrodeposited silver under potential control on an Au (111) surface from the solutions of 5mM AgNO₃/0.5M HNO₃ and 5mM KAg (CN)₂/0.5M KCN were investigated using Scanning Tunneling Microscopy (STM) in air. The silver films were deposited between 20mV and 100mV overpotential. From 5mM AgNO₃/0.5M HNO₃, silver was deposited like a single crystal along the gold substrate at 20mV overpotential. At 50mV overpotential large grains (300-500nm) were formed. Finally, at 100mV overpotential rough films were formed. From 5mM KAg (CN)₂/0.5M KCN, silver was deposited like a single crystal at 20mV overpotential, and between 50mV and 100mV, smaller grain deposition with 50-100nm particles were clearly deposited compared to the deposit from 5mM AgNO₃/0.5M HNO₃.

Effects of saturation flux density (Bs) of read/write head on the recording characteristics of perpendicular/longitudinal composite medium were investigated. It was found that the recording sensitivity was improved by applying the higher Bs head. In higher density region, the reproduced-voltage-enhancement was enlarged with high Bs head, however, at the higher MMF region, the read/write characteristics was worse because the head field penetration becomes broad. Therefore, it was necessary to optimize the medium parameters in account to the head parameter. © 1995 IEEE

The effect of mechanical strain on the surface properties of Si wafer was investigated as a model experiment to evaluate the correlation between the degree of the strain and the electrochemical properties of the Si wafer surface. Finite element structure analysis was applied to estimate the degree of strain, and the open circuit potential measurement was carried out to investigate the surface electrochemical property. The results of these experiments suggested that the mechanical stress induces strain to the Si crystal structure to change the surface reactivity. ©The Electrochemical Society.

We attempt to prepare the patterned electrode for the formation of nano particles using electrochemical deposition with the cathode whose surface has nano dot patterns. In particular, we applied electrodeposition of Pt and UV nano imprinting lithography (UV-NIL) to prepare the nano patterned electrode. In order to achieve higher activity, the deposition condition of Pt was optimized using additives such as polyethylene glycol (PEG). The surface activity of the Pt films was affected by molecular weight of PEG. It was revealed that the surface activity of the films deposited with the order of thousands of molecular weight of PEG indicated the highest effective current density among the examined films. The Pt films, which exhibited the highest current density, were adapted to fabricate nano-patterned electrode with 400 nm pith periodic structure using UV-NIL. ©The Electrochemical Society.

Sn-Cu films were electroplated on Cu seed layers of various thicknesses. The velocity of the diffusion of Cu atoms from a seed layer into the electroplated Sn-Cu film was investigated, focusing on the effect of microstructural properties of the film. It was found that the diffusion velocity of Cu from a Cu seed layer into the electroplated Sn-Cu film increased with a decrease in the thickness of the Cu seed layer. Moreover, the film microstructure was influenced by the thickness of the Cu seed layer. When the crystalline quality of the Cu seed layer was inferior, a large lattice mismatch developed at the interface between the electroplated Sn-Cu film and the Cu seed layer. As a result of this lattice mismatch, many lattice defects and stress may exist at the interface between the electroplated Sn-Cu films and the Cu seed layers. Therefore, the lattice mismatch was considered to be related to the high-diffusion velocity of Cu from the Cu seed layer. Furthermore, the high-diffusion velocity of Cu was found to cause whisker formation. (C) 2009 The Electrochemical Society. [DOI: 10.1149/1.3090179] All rights reserved.

The dendrite growth behavior of Li metal galvanostatically electrodeposited on Ni substrate in a LiClO(4)-propylene carbonate electrolyte solution was in situ observed by a laser scanning confocal microscope with a metallographic microscope. A Li dendrite precursor is stochastically evolved on Ni substrate probably through a solid electrolyte interphase layer produced by the surface chemical reaction between a reduced Li metal and an organic electrolyte. The measured length of randomly growing Li dendrite arms was statistically analyzed. The initiation period of the dendrite precursor becomes shorter with increasing current density and decreasing LiClO(4) concentration. Once it has been initiated, the ionic mass transfer rate starts to govern the growth process of the dendrite arm length, exceeding over the surface chemistry controlling step. The dendrite arm length averaged over the substrate surface grows linearly proportional to the square root of time. The lower the concentration of LiClO(4), the steeper the inclination of the line at 5 mA cm(-2), whereas the concentration dependence of inclination is not evident at 0.5 mA cm(-2). (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3486468] All rights reserved.

Effect of Tl on the electrodeposition behavior of Au was investigated by electrochemical analysis, total-reflection X-ray fluorescene analysis, XRD, glow discharge optical emission spectrometer (GD-OES) and hardness measurement. The deposition rate increased with an increase in the amount of Tl addition to the bath. Tl was co-deposited at the interface between the seed layer and the Au films, as well as in the films. In as-deposited condition, the Tl contained films exhibited higher hardness compared with the Tl-free films, while both of them showed almost the same hardness after annealing. It was suggested that the hardness is correlated with the crystal orientation of the grains.

This paper describes the development of Co alloy films thinner than 50 nm with high perpendicular magnetic coercivity using an electroless deposition process. In order to obtain these films, we used a Cu underlayer for a heteroepitaxial growth of the Co alloys and an optimized bath composition which included sodium hypophosphite and hydrazine as reductants. As a results, the perpendicular coercivity of the films turned to be higher 3000 Oe at the initial deposition stage with the thickness lower than 80 nm. In particular, the high perpendicular magnetic coercivity of the film as thin as 25 nm thick was obtained. These results indicate that electroless deposition is applicable for formation of the films with high perpendicular magnetic coercivity by optimizing the deposition conditions.

Laterally-enhanced growth of Au using electrochemical deposition from an electrode onto SiO2 surface modified with organic molecules for fabrication of nanogap electrodes was investigated. After modifying the SiO2 surface with self-assembled monolayers (SAMs) or dendrimer, electrodeposition was carried out and the enhanced lateral deposition was observed from the edge of Au electrode onto the SiO2 surface. In order to analyze the surface states modified with SAMs or dendrimer, X-ray photoelectron spectroscopy (XPS) were conducted and the existence of the organic molecules and Au ions on the SiO2 surface was confirmed. It was suggested that the enhanced lateral deposition was induced by the adsorbed Au ions. Furthermore, we tried to measure the electrical property of phthalocyanine molecular wire using the gap electrodes. In order to improve the contact state between the wire and the electrodes, electrodeposition was applied. As a result, improvement of contact state was observed from Current-Voltage characterization.

The electrochemical anodization of silicon films in aqueous solutions containing hydrofluoric acid was investigated. The films were deposited onto fused quartz chips from poly-crystalline, phosphorous doped silicon using magnetron physical vapor deposition in argon plasma. X-ray diffraction from these films showed that the atomic structure of silicon was amorphous. Current-potential profiles of the films in hydrofluoric acid solutions showed a linear increase in current with increasing anodic potential, unlike the diffusion limited profiles obtained from arsenic-doped silicon (100) crystals. In order to form microstructures within selected regions of the silicon, an epoxy resin was lithographically patterned onto the surface of the silicon prior to anodization. Three-dimensional profiles of the film's surface after removal of the resin revealed that the regions of silicon protected by the resin had formed microstructures.

The dendrite growth behavior of Li metal galvanostatically electrodeposited on Ni substrate in a LiClO(4)-propylene carbonate electrolyte solution was in situ observed by a laser scanning confocal microscope with a metallographic microscope. A Li dendrite precursor is stochastically evolved on Ni substrate probably through a solid electrolyte interphase layer produced by the surface chemical reaction between a reduced Li metal and an organic electrolyte. The measured length of randomly growing Li dendrite arms was statistically analyzed. The initiation period of the dendrite precursor becomes shorter with increasing current density and decreasing LiClO(4) concentration. Once it has been initiated, the ionic mass transfer rate starts to govern the growth process of the dendrite arm length, exceeding over the surface chemistry controlling step. The dendrite arm length averaged over the substrate surface grows linearly proportional to the square root of time. The lower the concentration of LiClO(4), the steeper the inclination of the line at 5 mA cm(-2), whereas the concentration dependence of inclination is not evident at 0.5 mA cm(-2). (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3486468] All rights reserved.

In order to elucidate the reactivity difference of hypophosphite ions used as reducing agents for electroless deposition on different metal surfaces, such as Pd and Cu, electronic structures of the activation states of hypophosphite ion oxidation on these surfaces were intensively analyzed by using Density Functional Theory (DFT). In the calculation, we focused on the dehydrogenation reaction which should be a rate-determining step in the elementary reaction steps. From the calculation results, a particular orbital interaction between the hypophosphite ion and the metal surface was observed. On Pd (111), the s-orbital of H in the hypophosphite ion interacts singly with the d- or p-orbital of Pd (111). This interaction induces an anti-bonding interaction between H and P in the hypophosphite ion, which is responsible for P-H cleavage. On the other hand, on Cu (111), the s-orbital of H and the s-orbital of P in a hypophosphite ion interact simultaneously with the p-orbital of Cu (111). This interaction barely induces an anti-bonding interaction between H and P in the hypophosphite ion. Such a difference in orbital interaction structures should be related to P-H cleavage activity and the reactivity difference of hypophosphite ion on each metal surface. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3623782] All rights reserved.

Two distinct morphologies were observed for copper films electrodeposited from an organic additive-free acid sulphate electrolyte near the limiting current density, namely facetted columns and spheroidal nodules. Facetted columns form for overpotentials eta = 200-280 mV while nodules form for eta &gt; 240 mV. Electron Back Scattering Diffraction (EBSD) was applied to cross-sections of the columnar films to determine the crystallographic orientation of individual grains. Over the first few microns, the substrate has a strong influence, but for greater thicknesses, the columnar film develops a strong &lt; 110 &gt; and weak &lt; 112 &gt; fibre texture. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3578016] All rights reserved.

In order to elucidate the reactivity difference of hypophosphite ions used as reducing agents for electroless deposition on different metal surfaces, such as Pd and Cu, electronic structures of the activation states of hypophosphite ion oxidation on these surfaces were intensively analyzed by using Density Functional Theory (DFT). In the calculation, we focused on the dehydrogenation reaction which should be a rate-determining step in the elementary reaction steps. From the calculation results, a particular orbital interaction between the hypophosphite ion and the metal surface was observed. On Pd (111), the s-orbital of H in the hypophosphite ion interacts singly with the d- or p-orbital of Pd (111). This interaction induces an anti-bonding interaction between H and P in the hypophosphite ion, which is responsible for P-H cleavage. On the other hand, on Cu (111), the s-orbital of H and the s-orbital of P in a hypophosphite ion interact simultaneously with the p-orbital of Cu (111). This interaction barely induces an anti-bonding interaction between H and P in the hypophosphite ion. Such a difference in orbital interaction structures should be related to P-H cleavage activity and the reactivity difference of hypophosphite ion on each metal surface. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3623782] All rights reserved.

The elementary steps of the reactions of hypophosphite ions with Cu, Ni, and Pd were calculated theoretically using Density Functional Theory (DFT) to demonstrate the reaction mechanism and gain insight at the molecular level. The elementary steps of these reactions are adsorption, dehydrogenation, and oxidation (hydroxyl base attack). In the adsorption step, hypophosphite ions adsorb onto each surface spontaneously with stabilities in the order of Ni (111) &gt; Pd (111) &gt; Cu (111). In the dehydrogenation step, hypophosphite ions dehydrogenate on Ni (111) and Pd (111) with small reaction barriers, whereas they react on Cu (111) with a large reaction barrier. The large reaction barrier on Cu (111) is not compensated for by the adsorption energy on the surface. In the oxidation step, dehydrogenated anions on each metal surface react spontaneously with the hydroxyl base. The reaction barriers on each metal surface in this step are not so significant compared to the adsorption energies on each surface, suggesting that a reaction barrier of hypophosphite ion oxidation should exist in the dehydrogenation step and only be observed for Cu (111). This proposition elucidates the experimental catalytic behaviors of metal surfaces in the electroless deposition process using hypophosphite ions. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3609000] All rights reserved.

To elucidate the influence of surface defects, such as steps, on the oxidation of a reducing agent that is used in the electroless deposition process, we theoretically analyzed the reaction behavior of hypophosphite ion around the defect using density functional theory calculations. The reason why we chose the hypophosphite ion is that it is a typical reducing agent and reacts through a universal reaction mechanism. In this analysis, we focused on the dehydrogenation reaction, which is the rate-determining step in the oxidation pathway. Pd and Cu surfaces were chosen as the metal surfaces, because they exhibit completely different catalytic activity from each other, both experimentally and theoretically. Our calculations showed that the surface defect stabilized the final state of dehydrogenation on both Pd and Cu surfaces, which indicates that the defect accelerates the oxidation of the hypophosphite ion. In the final state of dehydrogenation, dissociated hydrogen adsorbs on the hollow site, which appears on the slope of the defect. More detailed analyses of the final state indicate that the stabilization effect by the surface defect originates from the highly efficient interactions between the dissociated hydrogen and the slope. The molecular orbital structure on this slope is distorted, which leads to high electron density around the slope that enables the highly efficient interactions between the hydrogen and the slope. © 2013 Elsevier Ltd.

The acceleration effect of thiourea on an electroless Ni deposition reaction was analyzed through experimental and theoretical approaches. In the experimental approach, the entire deposition process was physically separated into the anodic and the cathodic reactions by preparing two cells connected by a salt bridge. The cells contained either a bath without metal (Ni) ions or a bath without a reducing agent (hypophosphite ions). The current flowing between the two separated baths increased when thiourea was added only to the anodic reaction bath, which indicated that the acceleration effect of thiourea was mainly on the anodic reaction of the hypophosphite ions. Based on this experimental result, in the theoretical calculation approach, a co-adsorption system consisting of thiourea, hypophosphite, and a Ni metal surface was analyzed using density functional theory. Among all the elementary steps of a hypophosphite reaction, thiourea primarily should promote the adsorption step owing to the following two factors. One was the molecular interaction between thiourea and the hypophosphite ion. The other was the restructuring of the electronic states of the Ni surface owing to the adsorption of thiourea, which enhanced the interaction between hypophosphite and its adsorption site on the Ni surface. © 2012 Elsevier Ltd.

The TiO2 nanotube system exhibits properties of interest in photoelectrochemical water splitting for hydrogen production, including high surface area and vectorial charge transport along the nanotube length. Changes in the anodizing electrolyte chemistry provide the means to control nanotube morphology as well as their length and width. Despite the large amount of work available on nanotube synthesis, however, a thorough assessment of the effect of anodization conditions on the photoelectrochemical performance is still unavailable. In this paper, we characterize TiO2 nanotubes produced by varying the water content of the organic anodization electrolyte and investigate the influence of the electrolyte on their photoelectrochemical performance. We find that the photocurrent efficiency of the nanotubes is optimized by using an 11 vol % water:ethylene glycol ratio. We also demonstrate that a double-anodization technique produces a cleaner surface, resulting in higher photon-to-current conversion efficiencies of up to 30% at 350 nm. Raman spectroscopy, X-ray diffraction, and electrochemical impedance studies support the notion that the variation in crystallinity as a function of water content is the main factor in determining the photocurrent efficiency of the nanotube system.

Thiourea is well known and widely used additive for controlling the rate of electroless Ni deposition, and it is known to show complicated behavior in acidic/alkaline electroless deposition baths. To understand this, several experiments and theoretical calculations were performed. In the experiments, the adsorption of thiourea and the reducing agent (i.e., hypophosphite ions) on a Ni surface was characterized with a high-selectivity component at a right angle down to the sub-monolayer level using surface-enhanced Raman spectroscopy. By comparing the results with those obtained from the theoretical calculation, co-adsorption of thiourea and hypophosphite ions on the Ni surface was confirmed. Moreover, the acceleration or suppression effects of thiourea on the oxidation of hypophosphite ions on a Ni surface in acidic/alkaline bath were analyzed from the experimental and computational perspectives. Accordingly, an explanation that unifies both the acceleration and suppression mechanisms of thiourea in terms of its own fundamental characteristics is proposed; this will be one of the most important processes for industrial applications of electroless Ni deposition. (C) 2013 The Electrochemical Society. All rights reserved.

The acceleration effect of thiourea on an electroless Ni deposition reaction was analyzed through experimental and theoretical approaches. In the experimental approach, the entire deposition process was physically separated into the anodic and the cathodic reactions by preparing two cells connected by a salt bridge. The cells contained either a bath without metal (Ni) ions or a bath without a reducing agent (hypophosphite ions). The current flowing between the two separated baths increased when thiourea was added only to the anodic reaction bath, which indicated that the acceleration effect of thiourea was mainly on the anodic reaction of the hypophosphite ions. Based on this experimental result, in the theoretical calculation approach, a co-adsorption system consisting of thiourea, hypophosphite, and a Ni metal surface was analyzed using density functional theory. Among all the elementary steps of a hypophosphite reaction, thiourea primarily should promote the adsorption step owing to the following two factors. One was the molecular interaction between thiourea and the hypophosphite ion. The other was the restructuring of the electronic states of the Ni surface owing to the adsorp

Thiourea is well known and widely used additive for controlling the rate of electroless Ni deposition, and it is known to show complicated behavior in acidic/alkaline electroless deposition baths. To understand this, several experiments and theoretical calculations were performed. In the experiments, the adsorption of thiourea and the reducing agent (i.e., hypophosphite ions) on a Ni surface was characterized with a high-selectivity component at a right angle down to the sub-monolayer level using surface-enhanced Raman spectroscopy. By comparing the results with those obtained from the theoretical calculation, co-adsorption of thiourea and hypophosphite ions on the Ni surface was confirmed. Moreover, the acceleration or suppression effects of thiourea on the oxidation of hypophosphite ions on a Ni surface in acidic/alkaline bath were analyzed from the experimental and computational perspectives. Accordingly, an explanation that unifies both the acceleration and suppression mechanisms of thiourea in terms of its own fundamental characteristics is proposed; this will be one of the most important processes for industrial applications of electroless Ni deposition. (C) 2013 The Electrochemical Society. All rights reserved.

To elucidate the influence of surface defects, such as steps, on the oxidation of a reducing agent that is used in the electroless deposition process, we theoretically analyzed the reaction behavior of hypophosphite ion around the defect using density functional theory calculations. The reason why we chose the hypophosphite ion is that it is a typical reducing agent and reacts through a universal reaction mechanism. In this analysis, we focused on the dehydrogenation reaction, which is the rate-determining step in the oxidation pathway. Pd and Cu surfaces were chosen as the metal surfaces, because they exhibit completely different catalytic activity from each other, both experimentally and theoretically. Our calculations showed that the surface defect stabilized the final state of dehydrogenation on both Pd and Cu surfaces, which indicates that the defect accelerates the oxidation of the hypophosphite ion. In the final state of dehydrogenation, dissociated hydrogen adsorbs on the hollow site, which appears on the slope of the defect. More detailed analyses of the final state indicate that the stabilization effect by the surface defect originates from the highly efficient interactio

Deposition processes of lithium in solid polymer [poly(ethylene oxide) (PEG)8+LiClO4] and gel [PEO8+propylene carbonate(PC) +LiClO4] electrolytes, as well as in the liquid (PC+LiClO4) one, were observed in situ using an optical microscope and their difference is discussed. It was confirmed that the dendritic growth of lithium, which appeared in the liquid electrolyte, is suppressed in the solid polymer due to the immobility of the electrolyte molecules, although non-uniform coverage of the cathode was observed because of its low conductivity. In contrast, the gel electrolyte possessed advantages of both the liquid and solid electrolytes, resulting in a smooth and uniform deposition in the current density region up to 2.0 mA cm(-2).

In order to elucidate the origin of magnetic properties and microstructure of electroless-deposited CoNiP films with perpendicular magnetic anisotropy, their initial growth processes were investigated mainly focusing upon the effects of bath factors. It was clarified that coercivity and grain size of the films changed widely with an increase in the ammonia concentration in the bath without varying the average film composition and crystal orientation. Detailed analysis of the growth processes clarified that an increase in ammonia concentration in the bath inhibited the growth of each crystallite, resulting in small grain size and coercivity, whereas it hardly affected the deposition activity of the catalytically-treated substrate surface and average film composition. (C) 1997 Published by Elsevier Science Ltd.

The growth process of etectroless nickel-phosphorous (NiP) films on nonconducting substrate was investigated quantitatively using tapping mode atomic force microscopy (TMAFM) with focus upon the nucleation density on the substrate surface. Three kinds of catalyzing processes were used for polyimide substrates to obtain nucleation densities of 900, 750, and 550 nuclei/μm2. The TMAFM observation showed that the film growth proceeds mainly through successive nucleation of fine "particles" with several nanometers in diameter and their three-dimensional growth, and that the nucleation density influences the state of aggregation of the particles and hence the resulting surface topography. The lower nucleation density developed the rougher surface with larger "grains" with a diameter of ca. 80 nm. However, the effect of nucleation density decayed with film growth and eventually vanished at a thickness of ca. 2000 nm due to successive nucleated. For comparison, the growth process of NiP on NiP coated Al substrate, which is used for rigid magnetic disk applications and has a higher nucleation density of 3000 nuclei/μm2, was also examined. This process resulted in a smooth surface without the formation of "aggregates." Based upon these results, the root-mean-square roughness and scaling analyses were performed to evaluate quantitatively the differences in growth process.

The oxidation mechanism of dimethylamine borane (DMAB) as a reductant fur an electroless deposition process was studied by an ab initio molecular orbital method. Two types of reaction pathways, via either three-coordinate borane molecules obtained by primary dehydrogenation reactions, or five-coordinate ones by primary additions of OH- for the oxidation of the DMAB, were examined. While the former pathway corresponds to the general oxidation mechanism of the reductant proposed by Meerakker, the present theoretical results support the latter one. Furthermore, it was clarified that an electron emission occurs when OH- adds to the four-coordinate compounds, which agrees with the Meerakker's mechanism. Results of the normal-mode analyses showed that the five-coordinate compounds are the transition states, The optimized geometries of monoanion five-coordinate molecules are nearly bipyramidal. The charge and spin-population analyses indicated that the axial bondings in the five-coordinate compounds are stabilized by the three-center three- or four-electron bondings. During the oxidation reaction of the DMAB, the change in the net charge of B is much smaller than that in the formal oxidation number, which is due to a great covalence. The existences of the five-coordinate borane molecules, which are first clarified by the present study, could be the key points of the catalytic activities of the deposited metals.

The oxidation mechanism of dimethylamine borane (DMAB) as a reductant fur an electroless deposition process was studied by an ab initio molecular orbital method. Two types of reaction pathways, via either three-coordinate borane molecules obtained by primary dehydrogenation reactions, or five-coordinate ones by primary additions of OH- for the oxidation of the DMAB, were examined. While the former pathway corresponds to the general oxidation mechanism of the reductant proposed by Meerakker, the present theoretical results support the latter one. Furthermore, it was clarified that an electron emission occurs when OH- adds to the four-coordinate compounds, which agrees with the Meerakker's mechanism. Results of the normal-mode analyses showed that the five-coordinate compounds are the transition states, The optimized geometries of monoanion five-coordinate molecules are nearly bipyramidal. The charge and spin-population analyses indicated that the axial bondings in the five-coordinate compounds are stabilized by the three-center three- or four-electron bondings. During the oxidation reaction of the DMAB, the change in the net charge of B is much smaller than that in the formal oxidation number, which is due to a great covalence. The existences of the five-coordinate borane molecules, which are first clarified by the present study, could be the key points of the catalytic activities of the deposited metals.

Effect of deposition site condition on the growth process of electroless CoNiP films was investigated by employing the intermediate 'treatment' step during the deposition. The effect of chemical species in the bath on the deposition sites, i.e., the film growth process, was examined using scanning electron microscopy (SEM) and atomic force microscopy (AFM). By changing the pH of the solutions for the 'treatment' step, it was found that the 'treatment' with higher pH solution resulted in the formation of smaller grains which possess lower perpendicular coercivity, Hc(perpendicular to). From these results, ammonia in the deposition bath results in the inhibition of the growth of crystallites, which leads lower Hc(perpendicular to). Based upon this, a model of the growth process of the CoNiP films was proposed. (C) 1999 Elsevier Science Ltd. All rights reserved.

The hardness of the soft gold electrodeposited from the thiosulfate-sulfite mixed ligand bath which we developed recently, has previously been found to increase with increasing sulfur content of the gold deposit. In the present study the mechanism of the sulfur inclusion was investigated by analyzing for sulfur gold deposits produced under various experimental conditions and also by observing weight gains resulting from the adsorption of sulfur-containing species on gold using the quartz crystal microbalance (QCM) technique. The results led us to conclude that the origin of the included sulfur is primarily the adsorbed Au(I)-thiosulfate species, (Au2S2O3)(ads), formed as an intermediate in the gold deposition reaction. (C) 2001 The Electrochemical Society.

Electroless gold deposition is known to take place on Ni-based substrates even when the conventional reducing agent is excluded from the autocatalytic bath containing thiosulfate and sulfite as ligands for gold ions. It is shown in this paper that the reaction of gold deposition from this bath on electroless Ni-B substrate is not autocatalytic but, instead, proceeds primarily by the mechanism of substrate catalysis with galvanic displacement playing a secondary role. It was established that sulfite serves as the reducing agent for the substrate-catalyzed gold deposition reaction. (C) 2002 The Electrochemical Society.

Characteristics of the gold deposit produced by the substrate (Ni)-catalyzed process in the thiosulfate-sulfite bath described in Part I of this series of papers are profoundly affected by bath composition and the composition and pretreatment of the substrate. This paper, Part II of a series of two, describes effects of those variables on the appearance, uniformity, morphology, and porosity of the gold deposit. (C) 2002 The Electrochemical Society.

Electroless gold deposition is known to take place on Ni-based substrates even when the conventional reducing agent is excluded from the autocatalytic bath containing thiosulfate and sulfite as ligands for gold ions. It is shown in this paper that the reaction of gold deposition from this bath on electroless Ni-B substrate is not autocatalytic but, instead, proceeds primarily by the mechanism of substrate catalysis with galvanic displacement playing a secondary role. It was established that sulfite serves as the reducing agent for the substrate-catalyzed gold deposition reaction. (C) 2002 The Electrochemical Society.

Characteristics of the gold deposit produced by the substrate (Ni)-catalyzed process in the thiosulfate-sulfite bath described in Part I of this series of papers are profoundly affected by bath composition and the composition and pretreatment of the substrate. This paper, Part II of a series of two, describes effects of those variables on the appearance, uniformity, morphology, and porosity of the gold deposit. (C) 2002 The Electrochemical Society.

An X-ray microcalorimeter is a cryogenic energy-dispersive spectrometer, which has an energy resolution almost comparable to that of conventional wavelength-dispersive spectrometers. Using a transition edge sensor (TES) as a temperature sensor, the energy resolution can be further improved. We have developed a new method of achieving an array of TES microcalorimeters for the purpose of X-ray imaging. To achieve this, mushroom-shaped X-ray microabsorbers formed using electrodeposition were applied. The temperature of the TES, which is easily degraded by thermal diffusion, was kept sufficiently low throughout the process to achieve practical use. On the bases of this new method, a 2 x 2 (x 4) array of TES microcalorimeters was fabricated and tested. A high energy resolution of 13.0 eV at 6 keV was achieved and the filling factor was improved to 83%. Although several issues still need to be investigated, we verified that our method is useful for fabricating a Ti-Au TES microcalorimeter array.

Formation of organosilane monolayers having various functional groups on silicon oxide surfaces for fabricating on-chip biosensing devices was investigated. Alkyl and perfluoro-alkyl functionalized monolayers were prepared by a chemical vapor deposition, and amino functionalized monolayers were formed by a liquid phase reaction. Each monolayer was confirmed to be closely packed and composed of single moiety species. A molecular patterning process using these organic monolayers was performed. The monolayer patterns were uniformly formed on the substrate by using ultraviolet light patterning and oxygen plasma ashing processes. The pH responsibility at the liquid/modified electrode interface was examined by using capacitor profiles of the structure of monolayer/silicon oxide/silicon. The amino modified surface showed good pH sensitivity of -44 mV/pH. This value was similar to that of the silicon nitride surface. On the other hand, the potential was not changed in any pH solutions in the case of the alkyl and perfluoro-alkyl monolayer-modified surface. It was demonstrated that the pH response of these surfaces was greatly affected by the variation of the functional group. Furthermore, by using the patterned monolayers, fabrication of a multichannel electrode for multiple detection of pH response was achieved.

An X-ray microcalorimeter is a cryogenic energy-dispersive spectrometer, which has an energy resolution almost comparable to that of conventional wavelength-dispersive spectrometers. Using a transition edge sensor (TES) as a temperature sensor, the energy resolution can be further improved. We have developed a new method of achieving an array of TES microcalorimeters for the purpose of X-ray imaging. To achieve this, mushroom-shaped X-ray microabsorbers formed using electrodeposition were applied. The temperature of the TES, which is easily degraded by thermal diffusion, was kept sufficiently low throughout the process to achieve practical use. On the bases of this new method, a 2 x 2 (x 4) array of TES microcalorimeters was fabricated and tested. A high energy resolution of 13.0 eV at 6 keV was achieved and the filling factor was improved to 83%. Although several issues still need to be investigated, we verified that our method is useful for fabricating a Ti-Au TES microcalorimeter array.

The heterojunction between Si(111) semiconductor and the well-ordered methyl monolayer was formed to investigate the channel conduction at the surface in the heterojunction structure. With the presence of water, the methyl monolayer/Si heterojunction structure showed switching action with a high trance-conductance of 2.8 x 10(-3) A/V under the application of bias voltage, while without the presence of water, such a switching behavior was not observed. The methyl monolayer/Si heterojunction structure worked as a p-type mode with the presence of water at the modified surface.

A photoassisted anodization process to fabricate arrays of uniform and straight macropores at selected areas of a Si wafer surface was developed. The front- and backside surfaces of n-type Si(100) wafers were coated with a thin Si3N4 layer, and the frontside layer was micro-patterned using photolithography and reactive ion etching to form an array of microscopic openings at selected areas. The inverted pyramid-shape micropits were formed at these openings by anisotropic etching using aqueous KOH solution; these pits act as the initiation sites for the anodization to form macropores. The electrochemical etching was carried out in aqueous HF solution under illumination from the backside of the wafer, on which Au/Cr electric contact was formed following removal of the Si3N4 layer. To improve the uniformity of the formation condition of the macropores at the selected area, holes were area-selectively generated by controlling the illumination condition during the anodization. For this, micropatterns were formed on the Au/Cr layer at the backside surface, which were aligned to those at the frontside surface. The parameters, such as HF concentration, current density, and wafer thickness, i.e., hole diffusion length, were optimized, and the arrays of uniform and high-aspect-ratio macropores were formed at the selected area of the domain at the silicon surface.

The spontaneous deposition of Ni on Si(100) surface in aqueous alkaline solution was investigated under various conditions. In a 0.1 M NiSO4 solution containing 0.2-0.5 M (NH4)(2)SO4, the optimum pH for the homogeneous deposition at 60-80degreesC at each set of operating conditions shifted in the high-pH direction as both (NH4)2SO(4) concentration and the operating temperature were decreased. The potential at which the deposition terminates and the deposition duration were determined from electrochemical open-circuit potential profiles. The different behaviors, observed at different pH levels, are discussed in terms of these potential measurements. Ultraviolet-visible absorption spectra of various Ni solutions used indicated that the deposition behavior was strongly affected by the composition of the Ni complex and the reactivity of Si surface. The deposition reaction efficiently proceeded when the Ni complex was present in a specific composition. The anodic reaction rate of Si decreased steeply when the solution temperature was lowered. The optimum condition for the homogeneous deposition was greatly affected by the reactivity of the Si surface rather than the composition of the complex, the higher pH favoring the overall reaction. (C) 2004 The Electrochemical Society. All rights reserved.

The heterojunction between Si(111) semiconductor and the well-ordered methyl monolayer was formed to investigate the channel conduction at the surface in the heterojunction structure. With the presence of water, the methyl monolayer/Si heterojunction structure showed switching action with a high trance-conductance of 2.8 x 10(-3) A/V under the application of bias voltage, while without the presence of water, such a switching behavior was not observed. The methyl monolayer/Si heterojunction structure worked as a p-type mode with the presence of water at the modified surface.

The recent adoption of copper interconnect technology by the semiconductor industry, has led to great interest in understanding the mechanisms of copper metal deposition onto silicon wafer surfaces from ultra pure water (UPW) solutions. We have studied these processes by using total reflection X-ray fluorescence (TXRF) and X-ray absorption near edge spectroscopy (XANES) in a grazing incidence geometry to determine the surface concentration and chemical state of copper atoms on intentionally contaminated Si surfaces. These measurements established that in deoxygenated UPW, copper is deposited on the silicon surface in the form of metallic nanoparticles with sizes up to 16 nm. However, in non-deoxygenated UPW, the copper is incorporated uniformly into the silicon surface oxide as Cu oxide.

Pd nanocluster seeds were formed on a soft magnetic underlayer (SUL) using an electrochemical substitution reaction, and were utilized as an intermediate layer for a Co/Pd multilayered ([Co/Pd](n)) perpendicular magnetic recording medium. A CoNiFeB film prepared with electroless deposition was used as SUL, which was immersed into a PdCl2 solution for the formation of Pd seeds. The Pd seeds were found to effectively reduce the size of magnetic domains in the [Co/Pd](n) film deposited on them. The optimization of the concentration of the PdCl2 solution and the use of the pretreatment process with a SnCl2 solution were effective to obtain the smooth SUL surface with fine Pd seeds as small as 5 nm. The 20 nm-thick [Co/Pd] n film deposited on the optimized Pd seeds/CoNiFeB SUL exhibited a high coercivity of 7.8 kOe and a small magnetic domain size of 69 nm. These results indicated that the combination of the Pd seeds and the electroless-deposited SUL was desirable in terms of the improvement not only in the magnetic properties of [Co/Pd] n media but also in the mass productivity of the underlayer. (C) 2006 Elsevier B.V. All rights reserved.

Oxidation reaction mechanisms of reductants for electroless Ag deposition process were investigated using density functional theory calculation, focusing upon behavior of the reaction intermediate species. It was indicated that the oxidation processes of reductants, such as dimethylamine borane, formaldehyde, and hypophosphite ion, on the Ag surface are initiated by addition of OH- and proceed via five-coordinate intermediate species. Catalytic activity of the Ag surface for the oxidation reaction of the reductants was investigated by using energy density analysis, focusing upon the local interaction of the species. The results indicated that the adsorption of the reductants onto the Ag surface is driven by destabilization of the reductant and stabilization of the Ag surface. It was also indicated that the destabilization of the five-coordinate intermediate species at the Ag surface is a key factor of the "catalytic activity" for the oxidation reaction. In the case of the reaction of formaldehyde, in which the Ag surface acts as catalyst, the intermediates were considerably activated at the Ag surface, whereas such an effect was not clearly seen with the hypophosphite ion, for which the Ag surface is not catalytic. It was also suggested that the activation of the intermediates is affected by coordination behavior of OH- species. (c) 2007 The Electrochemical Society.