Masao Miyake - Academia.edu (original) (raw)

Papers by Masao Miyake

Title Evidence for the Diffusion of Au Atoms into the Te UPD Layer Formed on a Au(111) Substrate ... more Title Evidence for the Diffusion of Au Atoms into the Te UPD Layer Formed on a Au(111) Substrate Author(s) Kawamura, Hiroyuki; Takahasi, Masamitu; Hojo, Nobuhiko; Miyake, Masao; Murase, Kuniaki; Tamura, Kazuhisa; Uosaki, Kohei; Awakura, Yasuhiro; Mizuki, Jun'ichiro; Matsubara, Eiichiro Citation Journal of The Electrochemical Society, 149(2): C83-C88 Issue Date 2002 Doc URL http://hdl.handle.net/2115/50232 Right © The Electrochemical Society, Inc. 2001. All rights reserved. Except as provided under U.S. copyright law, this work may not be reproduced, resold, distributed, or modified without the express permission of The Electrochemical Society (ECS). The archival version of this work was published in J. Electrochem. Soc. 2002 volume 149, issue 2, C83-C88. Type article

The Japan Society of Applied Physics, 2013

1. はじめに酸化亜鉛 (ZnO) は、3.37 eV のバンドギャップを持つ直接遷移型半導体であり、透明導電体材料としてだけでなく、半導体レーザーや青色発光ダイオードへの応用が期待されてい... more 1. はじめに酸化亜鉛 (ZnO) は、3.37 eV のバンドギャップを持つ直接遷移型半導体であり、透明導電体材料としてだけでなく、半導体レーザーや青色発光ダイオードへの応用が期待されている。これらの高い電気的および光学的特性を必要とする用途においては、10  cm オーダーの低抵抗率やエピタキシャル成長膜であることが求められる。一般的にエピタキシャル成長膜は乾式法で作製されてきたが、低コストの水溶液プロセスによっても ZnO のエピタキシャル成長は可能である。本研究では水溶液プロセスを用いて Ga を ZnO 膜中にドープし、低抵抗率の ZnO エピタキシャル膜を得ることを目的とする。 2. 実験方法基板には a 面サファイア単結晶を用い、ZnO 成長のためのシード層として膜厚 100 nm のエピタキシャル ZnO 膜をパルスレーザー堆積法で形成した。このシード層上に、フローリアクターを用いた水溶液プロセスによって ZnO 膜を成長させた。反応溶液には、ZnO を 25 °C で飽和させた 0.9 M NH3 0.1 M NH4NO3 3 mM クエン酸水溶液を用いた。この溶液をリアクター内の流路に流通させ、流路の上壁に固定した基板を 80 °C で 6 h 加熱することで、基板上に ZnO 膜を析出させた。反応溶液に GaCl3 を添加することで、Ga を含有する ZnO 膜を成長させた。析出膜の組成を EDX で評価した。結晶性の評価は XRD を用いて行い、電気的特性を van der Pauw 法による抵抗率およびホール効果測定によって評価した。 3. 結果反応溶液に添加した GaCl3 の濃度と ZnO 析出膜の Ga 含有率の関係を Fig. 1 に示す。溶液の GaCl3 濃度の増大とともに ZnO 析出膜の Ga 含有率は増大し、GaCl3 濃度 10 mM の時、Ga 含有率約 8% の ZnO 膜が得られた。これらの析出膜を XRD および極点図測定で分析した結果、GaCl3 濃度 9 mM 以下の溶液から析出した ZnO 膜はエピタキシャル成長していることが確認された。GaCl3 濃度を 10 mM まで増大させると、ZnO の 002 回折に加え、100 回折も検出され、配向性の低下が明...

Wide-bandgap oxide semiconductors have received significant attention as they can produce devices... more Wide-bandgap oxide semiconductors have received significant attention as they can produce devices with high output and breakdown voltage. p-Type conductivity control is essential to realize bipolar devices. Therefore, as a rare wide-bandgap p-type oxide semiconductor, NiO (3.7 eV) has garnered considerable attention. In view of the heterojunction device with Ga2O3 (4.5–5.0 eV), a p-type material with a large bandgap is desired. Herein, we report the growth of a Ni1-xMgxO thin film, which has a larger bandgap than NiO, on α-Al2O3 (0001) substrates that was developed using the mist chemical vapor deposition method. The Ni1-xMgxO thin films epitaxially grown on α-Al2O3 substrates showed crystallographic orientation relationships identical to those of NiO thin films. The Mg composition of Ni1-xMgxO was easily controlled by the Mg concentration of the precursor solution. The Ni1-xMgxO thin film with a higher Mg composition had a larger bandgap, and the bandgap reached 3.9 eV with a Ni1-x...

Scientific Reports, 2019

In this study, we explored the feasibility of WO3 surface layer formation on electrodeposited Al–... more In this study, we explored the feasibility of WO3 surface layer formation on electrodeposited Al–W alloy coatings by selective dissolution and heat treatment, with the aim of providing corrosion-resistant Al–W alloy coatings with photocatalytic self-cleaning properties under visible light illumination. The selective dissolution of Al and oxidation of residual W was carried out by immersing Al–W alloy films in an aqueous solution of nitric acid. A nanostructured H2WO4·H2O surface layer was formed on the alloy film by this process. The H2WO4·H2O layer was dehydrated to WO3 by heat treatment, yielding a multilayered WO3/Al–W alloy film with an approximately 300 nm thick WO3 layer. The WO3/Al–W alloy film exhibited photocatalytic self-cleaning, as demonstrated by the photodegradation of stearic acid and methylene blue. We also confirmed that selective dissolution and heat treatment did not significantly diminish the corrosion resistance of the Al–W alloy films.

MATERIALS TRANSACTIONS, 2018

Electrodeposition of AlW alloy films with high W contents has been carried out using 1-ethyl-3-me... more Electrodeposition of AlW alloy films with high W contents has been carried out using 1-ethyl-3-methylimidazolium chloride (EMIC) aluminum chloride (AlCl 3) ionic liquids containing tungsten(II) chloride (W 6 Cl 12). Although the corrosion resistance and hardness of the alloy films are expected to be improved with an increase in the W content, dense films with W contents higher than ³12 at% have not been obtained by electrodeposition to date. This study has demonstrated that electrodeposition using a EMICAlCl 3 W 6 Cl 12 bath with a lower AlCl 3 /EMIC molar ratio can yield AlW alloys with higher W contents. The maximum W content of the alloys electrodeposited using the EMIC1.5AlCl 3 bath reached 19.4 at%. The alloy films with up to ³18 at% W were dense and smooth, whereas those with >³18 at% W exhibited increased surface roughness. The hardness and Young's modulus of the dense and smooth 17.7 at% W film were determined by nano-indentation. The hardness of this film was confirmed to be higher than those of the AlW alloy films previously obtained from the EMIC2AlCl 3 baths.

Journal of The Surface Finishing Society of Japan, 2019

Electrodeposition of Al, which requires the use of a nonaqueous bath, is usually performed under ... more Electrodeposition of Al, which requires the use of a nonaqueous bath, is usually performed under an inert atmosphere of argon or nitrogen in a closed system, typically using a glove box, to protect the bath from hydrolysis. These operating conditions reduce productivity and increase Al electrodeposition process costs, thereby hindering industrialization. As described in this report, we demonstrate the electrodeposition of Al in dry air using dimethyl sulfone-AlCl 3-based baths. By obviating a closed system, this method can facilitate the industrialization of Al electrodeposition processes. Cyclic voltammetry, X-ray diffraction, and elemental analysis have confirmed Al metal electrodeposition in dry air. Hydrogen evolution was observed during electrodeposition in dry air, revealing that the current efficiency for the Al electrodeposition process was lower in dry air than in argon, although it remained higher than 90%. The poor appearance of the Al coating electrodeposited in dry air was resolved using an additive. Stability of the bath in dry air for over a month was confirmed.

Journal of Japan Institute of Light Metals, 2019

physica status solidi (a), 2013

Thin films of cuprous iodide (CuI), which is expected to be used in solid-state dye-sensitized so... more Thin films of cuprous iodide (CuI), which is expected to be used in solid-state dye-sensitized solar cells as a hole conductor, were formed by spin coating and subsequent annealing. The effects of the annealing conditions on the electrical properties of the CuI films were investigated by resistivity and Hall-effect measurements. The CuI films showed p-type conduction with resistivities of 0.3-5 Ω cm, carrier concentrations of 1 × 10 18-1 × 10 19 cm-3 and mobilities of 0.5-2 cm 2 V-1 s-1. It was found that the resistivities of the films annealed in air were slightly lower than those annealed in an Ar atmosphere because the carrier concentrations were higher in the former than in the latter. An increase in the mobility with the rise of annealing temperature was observed in the films annealed in Ar. However, annealing in air at high temperatures oxidized CuI to CuO.

International Journal of Electrochemical Science, 2017

In this study, we investigated the feasibility of a new process for the fabrication of Al-based c... more In this study, we investigated the feasibility of a new process for the fabrication of Al-based composite coatings containing TiO 2 particles with high photocatalytic activity. In the first step of this process, Al-TiO 2 composite coatings were electrodeposited in a dimethyl sulfone-aluminum chloride bath with suspended TiO 2 particles yielding Al-matrix composite coatings with uniformly dispersed TiO 2 particles. Subsequently, the electrodeposited Al-TiO 2 composite coatings were anodized in oxalic aqueous solution. Through this anodization step, the Al matrix was converted into an alumina layer with many nanopores extending from the surface of the coating toward the substrate. As a consequence, a porous alumina layer supporting TiO 2 particles was formed. The photocatalytic activity of the anodized composite coatings was confirmed to be higher than that of the as-deposited coatings.

Journal of The Electrochemical Society, 2017

The electrodeposition of Al-W alloy films in a Lewis acidic 1-ethyl-3-methyl-imidazolium chloride... more The electrodeposition of Al-W alloy films in a Lewis acidic 1-ethyl-3-methyl-imidazolium chloride (EMIC)-AlCl 3 ionic liquid using W 6 Cl 12 as the W ion source was investigated. W 6 Cl 12 dissolved in the ionic liquid at a higher concentration than other W ion sources used in previous studies. Potentiostatic electrodeposition was performed in a bath containing W 6 Cl 12 at a concentration of 49 mM. Dense Al-W alloy films containing up to 12 at.% W were electrodeposited at potentials more negative than 0 V vs. Al/Al(III). The deposition current density at >0 V was lower than 0.3 mA cm −2 , while that for Al-W alloy films was higher and reached 38 mA cm −2 at −0.5 V. The deposition of W was induced by the deposition of Al. At lower W concentrations, the Al-W alloy films were composed of a super-saturated solid solution, and in the W content range of 9-12 at.% they comprised an amorphous phase. Potentiodynamic polarization and nano-indentation showed that the Al-W alloy films containing 10-12 at.% W exhibited high pitting corrosion resistance, high hardness, and low Young's modulus.

Materials Chemistry and Physics, 2017

Various annealing conditions were examined for enhancing the electrical conductivity of galliumdo... more Various annealing conditions were examined for enhancing the electrical conductivity of galliumdoped ZnO (ZnO:Ga) epitaxial films grown from a low-temperature aqueous solution. The resistivity of the films decreased with increasing annealing temperature, accompanying increases in both the carrier concentration and mobility. However, the improvement obtained from 0.5 h of annealing was limited because the films spalled when the temperature exceeded ~300 °C. The temperature at which spalling of the films occurred depended on the annealing atmosphere, and it was lower in 5%H2-Ar than in air or vacuum. Thermal desorption spectroscopy showed that the cause of spalling was expulsion of H2O vapor from the interior of the film, indicating that water molecules or hydroxides were incorporated into the crystal during film growth. Analysis of the variations in electrical properties with increasing annealing duration revealed that the electrical properties were quickly improved upon heating before the film spalled. Thus, by limiting the annealing duration to ≤20 s, annealing could be performed at a temperature as high as 580 °C without spalling of the film, which yielded the lowest resistivity of 4.7 × 10-4 Ω cm. The annealed film exhibited transmittance as high as >75% in the visible spectrum.

Surface and Coatings Technology, 2017

Al-W alloy films with various W contents up to ~12 at% were prepared by electrodeposition using 1... more Al-W alloy films with various W contents up to ~12 at% were prepared by electrodeposition using 1-ethyl-3-methylimidazolium chloride (EMIC)-AlCl3 ionic liquids with different concentrations of W precursor, W6Cl12. The hardness (H) and Young's modulus (E) of the films were examined by nano-indentation. The films were composed of a single-phase fcc Al super-saturated solid solution, an amorphous phase, or

Surface and Coatings Technology, 2012

Aluminum (Al) coatings have been electrodeposited from dimethylsulfone (DMSO2)-AlCl3 electrolytes... more Aluminum (Al) coatings have been electrodeposited from dimethylsulfone (DMSO2)-AlCl3 electrolytes, but the coatings usually contained trace amounts of chlorine (Cl) and sulfur (S) as impurities. Since these impurities make the coatings hard and brittle, and moreover may adversely affect the corrosion-and oxidation-resistances of the Al coatings, it would be desirable to decrease their contents in the Al coatings. Examination of the Al coatings electrodeposited from the electrolytes with the addition of various amounts of trimethylamine hydrochloride (TMA) revealed that the Cl and S contents of the Al coatings decreased with increasing concentration of TMA in the electrolyte. The addition of TMA also brought about changes in the surface morphology and crystal orientation of the Al coatings. Preferential adsorption of TMA on the surface of the Al deposit was inferred to be a cause of the exclusion of Cl and S from the Al coating. As a result of the decrease in Cl and S contents, the Al coatings were softened.

Electrochimica Acta, 2014

This study investigated the use of novel organic solvent baths for the electrodeposition of alumi... more This study investigated the use of novel organic solvent baths for the electrodeposition of aluminum at near-ambient temperatures. It was found that Al metal can be electrodeposited from baths that were composed of 1,3-dimethyl-2-imidazolidinone (DMI) and AlCl3, with an AlCl3 concentration greater than 50 mol%. IR spectroscopy indicated that Al2Cl7ions were present in the baths that contained >50 mol% AlCl3, where the electrodeposition of Al occurs from Al2Cl7ion. The DMI/AlCl3 baths with AlCl3 concentrations between 59 and 64 mol% retained a single liquid phase without precipitation at 25 °C, and therefore, they can be used for Al electrodeposition near room temperature. Smooth Al films could be obtained by galvanostatic electrodeposition at 40 °C using a DMI/AlCl3 bath with the addition of a trace amount of 1,10-phenanthroline.

Journal of the Electrochemical Society, 2014

An aqueous process based on a unique flow-reactor design was developed for the preparation of gal... more An aqueous process based on a unique flow-reactor design was developed for the preparation of gallium-doped ZnO (ZnO:Ga) epitaxial films with a low electrical resistivity. In this process, a ZnO:Ga film was grown on a ZnO-seeded sapphire substrate heated at 80 • C under a constant flow of a reaction solution. The Ga content of the resulting films was found to increase in relation to the concentration of GaCl 3 used-0 to 9 mM GaCl 3-resulting in epitaxial growth of ZnO containing 0-5% Ga, whereas a polycrystalline ZnO film was produced with 10 mM GaCl 3. The electrical resistivity of the as-grown ZnO:Ga films varied from 0.2 to 2 cm, but was reduced by two to three orders of magnitude after the films were annealed in air at 300 • C. Thus, the lowest resistivity of 7 × 10-4 cm was obtained with an annealed film containing 2.5% Ga, whose carrier concentration and mobility were 7 × 10 20 cm-3 and 13 cm 2 V-1 s-1 , respectively. Furthermore, even though the non-doped ZnO film was rendered translucent by annealing, ZnO:Ga films with 1.8-4.0% Ga still exhibited transmittance as high as ∼80% in the visible spectrum.

physica status solidi (a), 2012

The fabrication of Al-doped ZnO films by an aqueous solution process using a continuous circulati... more The fabrication of Al-doped ZnO films by an aqueous solution process using a continuous circulation reactor was studied. By heating ZnO-saturated ammonia solutions containing 2-10 mM Al(NO3)3 with pH 10.7 at 90 ºC under ambient pressure, polycrystalline ZnO films with Al content of 1-2 at.% were deposited. The carrier concentration of ZnO films increased with increasing Al content, indicating that Al was successfully incorporated into the ZnO crystals. The Al-doped ZnO films had carrier concentrations of 10 19-10 20 cm-3 and mobilities of 0.7 to 7 cm 2 V-1 s-1 after annealing at 300 ºC in air.

MATERIALS TRANSACTIONS, 2011

A new cost-effective process to fabricate aluminide coatings was developed. Coating layers consis... more A new cost-effective process to fabricate aluminide coatings was developed. Coating layers consisting of nickel aluminides could be formed by electrodeposition of Al layers from a dimethylsulfone-AlCl 3 electrolyte on Ni substrates and subsequent annealing in air or vacuum at temperatures of 700-1150 C. Analysis of the intermetallic layers by XRD, SEM and EDX indicated the formation of Al 3 Ni and Al 3 Ni 2 at 700 C, AlNi at 900 C and 1000 C, and AlNi and AlNi 3 at 1150 C. The Annealing atmosphere did not affect the resulting intermetallic products.

Nature materials, Jan 24, 2011

Optoelectronic devices have long benefited from structuring in multiple dimensions on microscopic... more Optoelectronic devices have long benefited from structuring in multiple dimensions on microscopic length scales. However, preserving crystal epitaxy, a general necessity for good optoelectronic properties, while imparting a complex three-dimensional structure remains a significant challenge. Three-dimensional (3D) photonic crystals are one class of materials where epitaxy of 3D structures would enable new functionalities. Many 3D photonic crystal devices have been proposed, including zero-threshold lasers, low-loss waveguides, high-efficiency light-emitting diodes (LEDs) and solar cells, but have generally not been realized because of material limitations. Exciting concepts in metamaterials, including negative refraction and cloaking, could be made practical using 3D structures that incorporate electrically pumped gain elements to balance the inherent optical loss of such devices. Here we demonstrate the 3D-template-directed epitaxy of group III-V materials, which enables formation ...

Journal of The Electrochemical Society, 2011

Simple potentiostatic electrodeposition of platinum nanoparticles was performed on carbon black t... more Simple potentiostatic electrodeposition of platinum nanoparticles was performed on carbon black to prepare a carbon-supported Pt catalyst for polymer electrolyte fuel cells. The effect of ethylene glycol (EG) as an additive, deposition potential, and pH on the size and content of the electrodeposited Pt particles in the carbon powder was examined. Compared with the particles electrodeposited from a solution without EG, those with EG were smaller and dispersed well on the carbon. The electrodeposition at a more negative potential produced smaller particles. However, when the deposition potential was more negative than the equilibrium potential for H + /H2, Pt content higher than 30 wt% could not be obtained. In contrast, when the deposition potential was more positive than the equilibrium potential of H + /H2, the Pt content could be controlled by the amount of electrical charge, and increased up to 40 wt%. The electrodeposition from an alkaline solution yielded Pt particles with a mean 2 size of 4 nm, smaller than those obtained from a standard acidic solution.

Journal of The Electrochemical Society, 2012

Electrodeposition of Al coatings from dimethylsulfone (DMSO2)-AlCl3 baths with the addition of Zr... more Electrodeposition of Al coatings from dimethylsulfone (DMSO2)-AlCl3 baths with the addition of ZrCl4 was studied. Although pure Al coatings electrodeposited from the bath without ZrCl4 are lusterless, bright and smooth coatings were obtained when the ZrCl4 content in the baths was 0.005-0.015 mol per 10 mol DMSO2. The Zr content in the coatings varied up to 3.5 at% in proportion to the ZrCl4 content in the baths. The bright Al-Zr alloy coating showed high reflectance of 50-80% in the wavelength range of 450-1000 nm, whereas that of the matte pure Al coating was 10-20%. Morphological observations confirmed a reduction in the grain size of Al and surface leveling caused by the addition of ZrCl4 to the baths. Moreover, a strong <100> preferential orientation of Al crystals was observed for the bright coatings. The bright coating containing ~3.5 at% Zr had a higher corrosion potential by 0.1 V than the pure Al coating.