Fabrication of Functional Devices Based on Highly Ordered
Anodic Porous Alumina

Hideki MASUDA,^a,b Futoshi MATSUMOTO,^a and Kazuyuki NISHIO　^a,b

^aDepartment of Applied Chemistry, Tokyo Metropolitan University (1‐1 Minamiosawa, Hachioji, Tokyo 192‐03, Japan)
^bKanagawa Academy of Science and Technology (KAST) (5‐4‐30 Nishi‐Hashimoto, Sagamihara, Kanagawa 229‐1131, Japan)

Received March 29, 2004 ; Accepted April 30, 2004

Two types of preparation processes for highly ordered hole array structures of anodic porous alumina are described. In the naturally occurring ordering, long‐range ordered hole configuration was obtained under appropriate anodization conditions. The pretexturing process using a mold yielded ideally ordered hole configuration with a single domain structure over the sample. Obtained highly ordered anodic porous alumina membranes were applied to preparation of several types of functional nanodevices. In addition, replication processes using highly ordered anodic porous alumina as a starting structure are described. Highly ordered metal and semiconductor hole arrays prepared by the replication processes were applied to the preparation of several types of functional electrodes.

XAFS Study of Reaction Mechanism of Nano‐sized Manganese Dioxide
as Cathode Materials for Lithium‐ion Batteries

Shota KOBAYASHI, Yoshiharu UCHIMOTO, and Masataka WAKIHARA　^＊

Department of Applied Chemistry, Graduate School of Science and Engineering, Tokyo Institute of Technology (2‐12‐1, Ookayama, Meguro‐ku, Tokyo 152‐8552, Japan)

Received November 4, 2003 ; Accepted December 17, 2003

Nano‐sized particle manganese dioxides were synthesized by reduction process using NaMnO₄ precursor and fumaric acid as the reducing agent. Transmission electron microscopy examination showed size distribution of particles besides in the range of a few to 10nm. The high specific capacity of 350mAh g^-1 was observed during first charge. The electronic structure of synthesized samples before and after lithium ion intercalation and／or deintercalation was investigated by Mn L‐edge and O K‐edge X‐ray absorption spectroscopy.

Preparation of Thermally Stable Large Mesoporous SnO₂ Powders
by Employing a Triblock Copolymer

Yasuhiro SHIMIZU,^＊ Ayami JONO, Takeo HYODO, and Makoto EGASHIRA

Department of Materials Science and Engineering, Faculty of Engineering, Nagasaki University (1‐14 Bunkyo‐machi, Nagasaki 852‐8521, Japan)

Received November 19, 2003 ; Accepted March 9, 2004

Large mesoporous SnO₂ powders have been prepared from SnCl₄・5H₂O by a templating method using a triblock copolymer as a surfactant. Ethanol‐rinsing of resulting precipitates resulted in formation of large mesoporous SnO₂ powder having a broad pore size distribution with a maximum pore volume around 15 nm after calcination at 400℃ for 5h. Treatment of as‐precipitated products with phosphoric acid was not useful for improving the thermal stability of large mesoporous structure, whereas it prevented the growth of SnO₂ crystallites during the calcination. In contrast, large mesoporous SnO₂ powders having a sharp pore size distribution with a maximum pore volume around 3.5 nm and a specific surface area larger than 70m² g^-1 could be prepared by deionized water‐rinsing. It was revealed that aging treatment of as‐precipitated products led to a more uniform pore size distribution after the calcination, although the specific surface area decreased accordingly.

Mixed Proton‐electron Conducting Nanocomposite Based on
Hydrous RuO₂ and Polyaniline Derivatives for Supercapacitors

Kenji MACHIDA, Kei FURUUCHI, Myoungki MIN, and Katsuhiko NAOI　^＊

Graduate School of Technology, Tokyo University of Agriculture and Technology (2‐24‐16 Naka‐cho, Koganei, Tokyo 184‐8588, Japan)

Received November 22, 2003 ; Accepted March 11, 2004

Mixed proton‐electron conducting nanocomposites have been formed based on a hydrous ruthenium oxide and a proton‐conducting polymer for new supercapacitor energy storage nanomaterials with high capacitance and excellent rate capability. The nanocoating was carried out by polymerizing nano‐ordered poly ［3‐(4‐aminophenyl)propionic acid］ (PAPPA) thin film on the surface of the hydrous ruthenium oxide nanoparticles under ultrasonic irradiation. From the transmission electron microscopy observation, PAPPA film was found to form compactly and thinly on aggregated hydrous ruthenium oxide particles with diameter of ca. 20 nm (primary size). At a low scan rate of 2mV s^-1, the specific capacitance obtained for the nanocomposite electrode was 1210 F g^-1 which was higher than that for the ruthenium oxide nanoparticles itself (975 F g^-1). More importantly, the nanocomposite thin‐film electrode maintained its high capacitance (ca. 1000 F g^-1) even at an ultrafast scan rate of 1000 mV s^-1.

Electrochemical Growth of Single Crystal Alumina Nanoparticles
Using Al³⁺ Ion Conducting Solid Electrolytes

Nobuhito IMANAKA,^a＊ Young Woon KIM,^a Toshiyuki MASUI,^a
Takao SAKATA,^b and Hirotaro MORI　^b

^aDepartment of Applied Chemistry, Faculty of Engineering and Handai Frontier Research Center, Osaka University (2‐1 Yamadaoka, Suita, Osaka 565‐0871, Japan)
^bResearch Center for Ultra‐High Voltage Electron Microscopy, Osaka University (7‐1, Mihogaoka, Ibaraki, Osaka 567‐0047, Japan)

Received November 25, 2003 ; Accepted March 4, 2004

Single crystals of Al₂O₃ nanoparticles were successfully synthesized by dc electrolysis of the Al³⁺ ion conducting Al₂(WO₄)_2.4(MoO₄)_0.6 solid solution electrolyte at 11 V, 900℃. The particle size can be intentionally controlled by adjusting the electrolysis period：the particles distributed in the range of 100‐900 nm, and the average size was 440 nm for 3 days electrolysis, while the range and the size became 100‐1400 nm and 520 nm after the electrolysis for a week, respectively. Electron diffraction patterns for each particle evidenced that the particles grown were δ‐Al₂O₃ because the present electrochemical method was applicable at moderate temperatures around 900℃.

QCM Method to Evaluate Photocatalyst Ability of TiO₂

Yuuko NAKAMURA,^a＊ Yorinobu KATOU,^b and Seichi RENGAKUJI　^b

^aCenter for Instrumental Analysis, Toyama University (3190 Gofuku, Toyama 930‐8555, Japan)
^bDepartment of System Engineering of Materials & Life Science, Faculty of Engineering, Toyama University (3190 Gofuku, Toyama 930‐8555, Japan)

Received February 25, 2004 ; Accepted March 5, 2004

In order to evaluate the photocatalytic ability of TiO₂ film, quartz crystal microbalance (QCM), which is a gravitation method, was employed instead of the conventional absorption method. The advanced sol‐gel method, which can control thickness to the several tenths of a nanometer level, was applied to the coating on the QCM element. India ink coated on the QCM element was used as the model material for the photo‐decomposition. The amount of decomposition during UV light irradiation was detected by the frequency‐shift. This method was also tested in application to an organic gas sensor.

Preparation of Pt Monolayer Islands
Using Self‐assembled Monolayer Technique

Anusorn KONGKANAND and Susumu KUWABATA　^＊

Department of Materials Chemistry and Frontier Research Center, Graduate School of Engineering, Osaka University (2‐1 Yamada‐oka, Suita, Osaka 565‐0871, Japan)

Received November 26, 2003 ; Accepted March 4, 2004

Preparation technique of Pt monolayer islands has been developed by combining two techniques；the preparation of nanopores in a self‐assembled monolayer of alkanethiol and deposition of Pt monolayer using Cu adlayer as a reducing agent. This novel technique gives remarkably uniform monolayer islands for island sizes ranging from 3 to 11 nm.

Fabrication of Pt Nanoparticles‐polypyrrole Composite
for Electrocatalyst

Shigehito DEKI,^＊ Heisuke NISHIKAWA, and Minoru MIZUHATA

Department of Chemical Science and Engineering, Faculty of Engineering, Kobe University (1‐1 Rokkodai‐cho, Nada, Kobe 657‐8501, Japan)

Received November 26, 2003 ; Accepted March 8, 2004

Preparation of polypyrrole (PPy) containing Pt nanoparticles was attempted. The oxidation of pyrrole into polypyrrole proceeded by H₂PtCl₄, simultaneously reducing Pt(IV) to Pt(０). The Pt particles were obtained with average size of 2 nm and fairly narrow size distribution. Moreover, the maximum content of Pt reached over 20 wt％ without any evidence of aggregation. The optimum ［Pt］／［Py］, for obtaining successful Pt／PPy composite including highly concentrated Pt and exhibiting high electrical conductivity, was determined at R＝0.6.

Suppression of Substrate Heating in the Sputter‐deposition of ITO
Films

Kentaro FUNATSU, Hiro‐omi KATO, and Yoichi HOSHI

Faculty of Engineering, Tokyo Polytechnic University (1583 Iiyama, Atsugi‐shi, Kanagawa 243‐0297, Japan)

Received November 26, 2003 ; Accepted March 19, 2004

Suppression of substrate heating during film deposition is necessary to realize a high rate deposition of ITO films on plastic film substrate. In a sputter‐deposition of the film using a conventional magnetron sputtering system, heating power incident into substrate was measured and mechanisms of the substrate heating were investigated precisely. Most of the incidence power into the substrate is originated in the bombardment of high‐energy secondary electrons emitted from the target, and can be reduced to 1/9 by removing the electron bombardment. Compared with the total incidence power to the substrate, the heat of formation of the film was estimated to be below 1/50. This suggests that further reduction of the incidence power into substrate will be possible in the deposition using a conventional magnetron sputtering system.

Nano‐scale Crystal Formation in Copper Magneto‐electrodeposition
under Parallel Magnetic Fields

Ryoichi MORIMOTO,^a＊ Atsushi SUGIYAMA,^b and Ryoichi AOGAKI　^c

^aSaitama Industrial Technology Center (3‐12‐18 Kamiaoki, Kawaguchi, Saitama 333‐0844, Japan)
^bDomestic Research Fellow, Japan Society for Promotion of Science (3‐12‐18 Kamiaoki, Kawaguchi, Saitama 333‐0844, Japan)
^cPolytechnic University (4‐1‐1, Hashimotodai, Sagamihara, Kanagawa 229‐1196, Japan)

Received November 29, 2003 ; Accepted March 8, 2004

Nano‐scale crystal formation in copper magneto‐electrodeposition under parallel magnetic fields was examined with X‐ray diffraction. In 30 mol m⁻³ copper sulfate solution, below the overpotential −0.2 V, the average crystal size decreased with magnetic field, whereas beyond −0.2 V, the average crystal size increased in the higher range. The atomic force microscope images of the deposits also showed the same tendency.

Development of Bi Electrodeposition Process for Fabricating
Microabsorber Array for High Sensitive X‐ray Imaging Sensor

Hirotaka SATO,^a Hideomi KOBAYASHI,^a Hiroyuki KUDO,^b Toshimitsu IZUMI,^b
Takayuki HOMMA,^a＊ Tetsuya OSAKA,^a Shuichi SHOJI,^b Yoshitaka ISHISAKI,^c
Ryuichi FUJIMOTO,^d and Kazuhisa MITSUDA　^d

^aDepartment of Applied Chemistry and ^bDepartment of Electrical Engineering and Bioscience, Waseda University (Okubo, Shinjuku, Tokyo 169‐8555, Japan)
^cDepartment of Physics, Tokyo Metropolitan University (Minami‐Osawa, Hachioji, Tokyo 192‐0397, Japan)
^dHigh Energy Astrophysics Division, Institute of Space and Astronautical Science, Sagamihara (Kanagawa 229‐8510, Japan)

Received November 29, 2003 ; Accepted March 10, 2004

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.

Electrocatalytic Oxidation of Sugars at Ag Ad‐layer Modified
Au(100) Electrodes in Alkaline Solutions

Isao TANIGUCHI,^a＊ Yasuhiro NONAKA,^a Zekerya DURSUN,^a Sami BEN AOUN,^a
Changchun JIN,^a Gyeong Sook BANG,^a Tesshu KOGA,^a and Tadashi SOTOMURA　^b

^aDepartment of Applied Chemistry and Biochemistry, Kumamoto University (2‐39‐1, Kurokami, Kumamoto 860‐8555, Japan)
^bMatushita Electric Industrial Co., Ltd. (3‐1 Moriguchi, Osaka 570‐8501, Japan)

Received November 30, 2003 ; Accepted March 18, 2004

Ag ad‐layer modified Au(100) and Au(111) electrodes showed excellent catalytic behavior for oxidation of aldose type (such as glucose, maltose, galactose and xylose) sugars. The best catalytic effect was observed at a (√2×5√2)R45° Ag‐Au(100) electrode, 2/5 monolayer of Ag on Au(100), where the oxidation of glucose began at −0.7 V (vs. Ag／AgCl) with a negative shift of ca. 0.2 V in oxidation potential compared to the oxidation at a bare Au(100) electrode. As was observed at a (√3×√3)R30° Ag‐Au(111) electrode, 1/3 monolayer of Ag on Au(111), the catalytic oxidation of glucose was also seen at Au(111) film electrodes with large surface areas after deposition of Ag ad‐layer.

Synthesis and Characterization of Conducting Polymer Nanorods
by Using Electropolymerization in Nanoporous Template

Yuko MAEDA,^a Fumiko CHIBA,^b Kikuno IIDA,^b Kenro TOTANI,^b Kenji OGINO,^a Takayuki ISHIBASHI,^c Hari Singh NALWA　,^d and Toshiyuki WATANABE　^b＊

^aGraduate School of Bio‐Applications Systems and Engineering, Tokyo University of Agriculture and Technology (2‐24‐16 Nakacho, Koganei, Tokyo 184‐8588, Japan)
^bDepartment of Organic and Polymer Materials Chemistry, Faculty of Technology, Tokyo University of Agriculture and Technology (2‐24‐16 Nakacho, Koganei, Tokyo 184‐8588, Japan)
^cDepartment of Applied Physics, Faculty of Technology, Tokyo University of Agriculture and Technology (2‐24‐16 Nakacho, Koganei, Tokyo 184‐8588, Japan)
^dStanford Scientific Corporation (25650 North Lewis Way, Stevenson Ranch, CA 91381, USA)

Received December 1, 2003 ; Accepted March 4, 2004

Uniform size nanorods consisting of polypyrrole were synthesized via electropolymerization using a porous alumina template. The dispersion of polymer particles was obtained by dissolving the template in an alkaline solution followed by dialysis with distilled water. SEM‐EDS and TEM techniques revealed that synthesized polypyrrole nanoparticles are rod‐shaped having a diameter of 20 nm.

Effect of Dissolved Gas on Deposition of Pd Particles on Si Substrate

Masami SHIBATA　^＊ and Kazuki NEBASHI

Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi (4‐3‐11 Takeda, Kofu 400‐8511, Japan)

Received December 4, 2003 ; Accepted March 18, 2004

In this study, the effect of a dissolved gas on Pd deposition at the silicon substrate in the solutions saturated with various gases in a glove box is investigated. The number of Pd nanoparticles deposited in the solution saturated with the mixed gas (10％ H₂ and 90％ N₂) is less than with the air and pure oxygen gas. Also, the average size of Pd particles deposited in the hydrogen atmosphere is larger than in the air and oxygen atmospheres. In the solution containing the dissolved H₂ gas, the Pd nucleus significantly grows, and there are small numbers of Pd particles, because H₂ oxidation occurs only at the Pd nucleus.

Kinetic Study of Direct Bioelectrocatalysis of Dioxygen Reduction with
Bilirubin Oxidase at Carbon Electrodes

Seiya TSUJIMURA, Takaaki NAKAGAWA, Kenji KANO　,^＊ and Tokuji IKEDA　^＊

Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University (Sakyo, Kyoto 606‐8502, Japan)

Received December 4, 2003 ; Accepted February 14, 2004

Direct electron transfer‐type bioelectrocatalysis of four‐electron reduction of dioxygen was successfully realized with bilirubin oxidase (BOD, EC 1.3.3.5, from Myrothecium verrucaria) at carbon electrode surfaces with high crystal graphite edge density. It was found that adsorbed BOD functions as a biocatalyst. The current‐potential curves were interpreted by considering the enzyme catalytic constant, surface electron transfer kinetics, surface concentration of BOD, and the formal potential of BOD. The analysis suggested that the standard surface electron transfer rate constant and surface coverage of “active" enzyme depend strongly on functional groups and／or nano‐structure of carbon electrode surface.

Structure of DNA‐Ru(bpy)₃²⁺ Complex and Its Application to
Orange Color Electroluminescence Device

Norihisa KOBAYASHI,^＊ Masatsugu HASHIMOTO, and Kazuhiko KUSABUKA

Department of Information and Image Sciences, and Graduate School of Science and Technology Chiba University (Chiba 263‐8522, Japan)

Received December 4, 2003 ; Accepted March 16, 2004

DNA‐Ru(bpy)₃²⁺ complex was prepared to study EL characteristics. Ru(bpy)₃²⁺ was associated with duplex of DNA by the interaction such as intercalation in the pH 3 aqueous solution. It was revealed that the EL device composed of DNA‐Ru(bpy)₃²⁺ complex exhibited extremely faster response than the other Ru(bpy)₃²⁺ based EL devices. The emission mechanism was discussed. DNA‐Ru(bpy)₃²⁺ complex is expected to be applicable to an optoelectro‐functional molecular wire.

Photoelectrochemical Behavior of the Pt／TiO₂ Nanocomposite Electrodes Prepared by Co‐sputter Deposition

Takeshi SASAKI,^a＊ Naoto KOSHIZAKI,^a Jong‐Won YOON,^a Satoshi YAMADA,^b
Michio KOINUMA,^c Masayuki NOGUCHI,^c and Yasumichi MATSUMOTO　^c

^aNanoarchitectonics Research Center, National Institute of Advanced Industrial Science and Technology (Central 5, 1‐1‐1 Higashi, Tsukuba, Ibaraki 305‐8565, Japan)
^bDepartment of Aerospace Engineering, School of Science and Engineering, Teikyo University (1‐1 Toyosatodai, Utsunomiya 320‐8551, Japan)
^cDepartment of Applied Chemistry and Biochemistry, Faculty of Engineering, Kumamoto University (2‐39‐1 Kurokami, Kumamoto 860‐8555, Japan)

Received December 5, 2003 ; Accepted March 22, 2004

The photoelectrochemical behavior of the Pt／TiO₂ nanocomposite electrodes in aqueous 0.1M Na₂SO₄ electrolyte was investigated. Pt／TiO₂ nanocomposite films (platinum nanoparticles dispersed in TiO₂ films) and TiO₂ films deposited on ITO glass substrates by the sputtering were used as electrodes. Anodic photocurrent of Pt／TiO₂ nanocomposite electrode at potential higher than 0.5 V vs. Ag／AgCl under the irradiation of Xenon lamp was one order smaller in the magnitude than that of TiO₂ electrode, resulting from the recombination between hole and electron at Pt particles. Anodic photocurrent of Pt／TiO₂ nanocomposite electrode at 1.0 V vs. Ag／AgCl was observed at the wavelength region of visible light. Pt／TiO₂ nanocomposite electrodes have remarkably different photoelectrochemical behaviors compared with that of pure TiO₂ electrodes.

Co‐deposition Characteristics of Nanodiamond Particles
in Electrolessly Plated Nickel Films

Hiroshi MATSUBARA,^＊ Mikinori KOBAYASHI, Hiroshi NISHIYAMA,
Nobuo SAITO, Yasunobu INOUE, Masao MAYUZUMI　^a

Analysis and Instrumentation Center, Nagaoka University of Technology (1603‐1 Kamitomioka, Nagaoka 940‐2188, Japan)
^aTokyo Diamond Tools MFG. Co., Ltd. (2‐3‐5 Nakane, Meguro, Tokyo 152‐0031, Japan)

Received December 15, 2003 ; Accepted March 17, 2004

Co‐deposition characteristics of refined nanodiamond particles (5 nmφ) into electrolessly plated nickel films were studied. Effects of concentration, temperature and pH of the baths were investigated. It is suggested that nanodiamond particles are co‐deposited into the film after adsorption on a surface of the plated film. The authors found that the content of diamond particles in the film increased with decreasing deposition rate and decreasing hydrogen evolution rate accompanied by plating reaction. The content did not exceed 2 ％ when we use an ordinary plating solution; ammoniacal‐citrate nickel plating bath.

Electrochemical Determination of Charge Transfer Direction of
“Center‐to‐Edge" Phosphorus(V) Porphyrin Arrays

Yasuko TAKEUCHI,^a Kazutaka HIRAKAWA,^b Kimihiro SUSUMU,^c
and Hiroshi SEGAWA　^a,b＊

^aDepartment of Applied Chemistry, Graduate School of Engineering, The University of Tokyo (3‐8‐1 Komaba, Meguro‐ku, Tokyo 153‐8902, Japan)
^bDepartment of Chemistry, Graduate School of Arts and Sciences, The University of Tokyo (3‐8‐1 Komaba, Meguro‐ku, Tokyo 153‐8902, Japan)
^cDepartment of Chemistry, University of Pennsylvania (231 South, 34th Street, Philadelphia, PA 19104‐6323, U.S.A.)

Received December 30, 2003 ; Accepted March 8, 2004

The redox properties of a series of “center‐to‐edge" phosphorus(V) porphyrin arrays composed of similar porphyrin units were investigated by cyclic voltammetry. From the assignments of the reduction peaks, it was revealed that small difference of electron‐donating ability of the axial ligands and the electrostatic intramolecular interaction affect their redox potentials. Moreover, the comparison of the reduction potentials enables to determine the polarization direction of the charge transfer excited‐state of the porphyrin arrays.

Fabrication of Metal‐oxide Nanoparticles by the Liquid Phase
Deposition Method in the Heterogeneous System

Shigehito DEKI,^＊ Akiyoshi NAKATA, and Minoru MIZUHATA

Department of Chemical Science and Engineering, Faculty of Engineering, Kobe University (1‐1 Rokkodai‐cho, Nada, Kobe 657‐8501, Japan)

Received January 9, 2004 ; Accepted March 8, 2004

For the development of the preparation method of size‐controlled nanoparticles, we applied the liquid phase deposition (LPD) method to the reverse micelle (RM) reaction contained TritonX‐100 and 1‐hexanol. We prepared two kinds of metal oxide nanoparticle; TiO₂ and SnO₂. The average sizes of nanoparticles were 5.9 nm and 3.0 nm for TiO₂ and SnO₂, respectively. The size distribution was narrow, and crystallization of the particles was promoted by the nano‐scale reaction field. The bandgap was calculated from UV‐Vis spectra. The bandgap energy of SnO₂ nanoparticles showed a larger value at 4.6 eV, whereas that of TiO₂ nanoparticles showed a constant value at 3.2 eV. The quantum effect causes the variation of the bandgap, however, the effect depends on the kinds of the metal oxide.

High‐quality Growth of TiO₂ Thin Film from Its Precursor Solution
by New Sol‐gel Method

El‐Maghraby MOHAMED,^a Yuuko NAKAMURA,^b＊ Yasuhiro FUJII,^c
Michiyo KAMIYA,^d and Seichi RENGAKUJI　^e

^aVenture Business Laboratory, Graduate School of Materials Science and Technology, Faculty of Engineering, Toyama University (3190 Gofuku, Toyama 930‐8555, Japan)
^bCenter for Instrumental Analysis, Toyama University (3190 Gofuku, Toyama 930‐8555, Japan)
^cELNA CO., LTD. (30 Ta Torahime‐machi, Higashiazai‐gun, Siga 529‐0142, Japan)
^dVenture Business Laboratory, Toyama University (3190 Gofuku, Toyama 930‐8555, Japan)
^eDepartment of System Engineering of Materials & Life Science, Faculty of Engineering, Toyama University (3190 Gofuku, Toyama 930‐8555, Japan)

Received October 29, 2003 ; Accepted March 17, 2004

TiO₂ thin film, which has high photocatalytic property, was fabricated from its precursor solution by spin‐coating method. The solution was prepared by the recently developed advanced sol‐gel method. This liquid process is based on the hydrolysis and polymerization of Ti alkoxide in mixed solvent of butanol and toluene. The obtained solution was transparent without precipitate and stable, and thus the metal oxide precursor solution was prepared. TG‐DTA analysis of the powder dried in vacuum and XRD patterns of the annealed films showed that the crystalline anatase phase appeared at 300℃. This temperature is lower than that obtained from the conventional sol‐gel method. From AFM imaging, the surface of TiO₂ thin film coated on quartz or glass substrates appeared flat. The photocatalytic activity of TiO₂ thin film prepared by advanced sol‐gel method was higher than that prepared by conventional sol‐gel method.

Adsorption of Sulfur and Growth of Copper Sulfide
on Cu(100) and Cu(110) in Alkaline Solution

Junji INUKAI,^a,b Masatoshi SUGIMASA,^b Shueh‐Lin YAU,^c,d and Kingo ITAYA　^b,c＊

^aNICHe, Tohoku University (Aoba‐yama 10, Sendai 980‐8579, Japan)
^bDepartment of Applied Chemistry, Faculty of Engineering, Tohoku University (Aoba‐yama 0.4, Sendai 980‐8579, Japan)
^cCREST, JST (4‐1‐8 Kawaguchi, Saitama 332‐0012, Japan)
^dDepartment of Chemistry, National Central University (ChungLi, 320, Taiwan)

Received November 25, 2003 ; Accepted March 4, 2004

Adlayer structures of S on Cu(100) and Cu(110) were investigated by using in situ scanning tunneling microscopy (STM) in alkaline solution. On Cu(100), the adsorbed S formed a (2₁0₃) structure, whereas a c(2×8) structure was found on Cu(110). Both structures were stable in the double‐layer potential region. At anodic potentials, Cu₂S was formed on both surfaces. On Cu(100), patches of islands with Cu₂S(100) surfaces were observed. On Cu(110), the surface was highly roughened as a result of the formation of Cu₂S.

Ab Initio Molecular Orbital Study of the Electron Emission Mechanism
of TiCl₃ as a Reductant for an Electroless Deposition Process

Takuya SHIMADA,^a Isao KOMATSU,^a Takayuki HOMMA,^a＊ Hiromi NAKAI,^b＊
and Tetsuya OSAKA　^a

^aDepartment of Applied Chemistry, School of Science and Engineering, Waseda University (Okubo, Shinjuku‐ku, Tokyo 169‐8555, Japan)
^bDepartment of Chemistry, School of Science and Engineering, Waseda University (Okubo, Shinjuku‐ku, Tokyo 169‐8555, Japan)

Received November 29, 2003 ; Accepted March 5, 2004

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 Pd₄ cluster as a model surface. It was suggested that the Pd₄ 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.

Chemical Etching Behavior and Mechanism of Undoped GaAs
in Tartaric Acid ‐ hydrogen Peroxide Solution Systems

Kazuhiro SHIGYO,^＊ Sonoko UMEMURA, and Kazumasa KAWASE

Mitsubishi Electric Corporation, Advanced Technology R&D Center (Tsukaguchi Honmachi 8‐1‐1, Amagasaki, Hyogo 661‐8661, Japan)

Received November 25, 2003 ; Accepted March 22, 2004

The chemical etching behaviors of undoped GaAs (100) in tartaric acid (C₄H₆O₆) and hydrogen peroxide (H₂O₂) aqueous solutions is investigated for the fabrication of nano‐structures applied for opt‐electronic and photonic devices. The role of the constituents of the etching solution (H₂O₂ and C₄H₆O₆) is reported clearly. The etching rate of GaAs increases with increased concentration of H₂O₂, and the cross‐sectional etching profile changes from a non‐isotropic to an isotropic shape as the H₂O₂ concentration decreases. X‐ray photoelectron spectroscopy studies clarify that the H₂O₂ oxidizes the GaAs surface, and C₄H₆O₆ removes the oxide layers. Photoelectron peaks attributed to arsenic oxides are obtained from the surface of a GaAs specimen chemically etched in a C₄H₆O₆＋H₂O₂ aqueous solution. It seems that successive oxidation and dissolution of GaAs are performed during chemical etching in C₄H₆O₆＋H₂O₂, and gallium oxide may preferably dissolve into the solution.