光電極反応と光機能界面

1997 年度 実績報告書

• 研究課題/領域番号: 09237105
• 研究種目: 重点領域研究
• 研究機関: 大阪大学
• 研究代表者: 中戸 義禮 大阪大学, 大学院・基礎工学研究科, 教授 (70029502)
• 研究分担者: 中林 誠一郎 埼玉大学, 理学部, 助教授 (70180346) ; 箕浦 秀樹 岐阜大学, 工学部, 教授 (40021612) ; 橋本 和仁 東京大学, 先端科学技術研究センター, 教授 (00172859) ; 野坂 芳雄 長岡技術科学大学, 工学部, 教授 (30134969)
• キーワード: 原子レベル構造制御 / 終端結合 / 太陽エネルギー交換 / ナノ構造体 / 電気化学的エピタキシャル成長 / 磁性材料 / 光制御 / 界面電子移動ダイナミクス

研究概要

本研究では、電気化学的な手法による半導体表面の原子レベルでの構造制御、ならびに、界面光電気化学過程のダイナミクスの解明と、これらによる新しい光機能界面の創製を目的に、研究を行った。半導体表面の原子レベルでの構造制御に関連して、シリコン(Si)半導体表面の終端結合の制御を試み、濃厚ハロゲン化水素酸処理によりハロゲン終端結合が生成して、Siの表面バンドエネルギー(フラットバンド電位)が変化し、光起電力が向上することを見出した。さらに、これを利用して、Siチップの表面の非対称化をはかり、一つのSiチップだけを用いて高効率な太陽エネルギーの化学エネルギーへの変換システムを作ることができることを示した。半導体表面上のナノ構造体の形成に関しては、多結晶n-TiO_2電極を硫酸中で光アノード溶解させることにより数百ナノメートルの大きさの規則正しい構造の細孔が形成されることを見出した。また、半導体薄膜の電気化学的エピタキシャル成長に関しては、金やSi単結晶を基板に用い、交互ディッピング堆積法により、(001)方向に強く配向したCdS多結晶薄膜を得た。また、電着液の組成を詳しく検討して、(002)配向の高結晶性の六角形のCdS結晶粒が得られることも明らかにした。電気、光などの外部刺激により制御可能な新しいタイプの磁性材料の開発についても実験および理論の両面から研究を進め、プルッシアンブルーにTiO_2光触媒をハイブリッドさせた薄膜において、これにメタノールとカリウムイオンの存在下で紫外光を照射すると、薄膜が(5K以下の温度において)強磁性体から常磁性体に変化する(すなわち光により磁性を制御できる)ことを見出した。半導体電極上のダイナミクスについては、半導体電極上の固定した色素分子の光誘起電子移動反応のダイナミクスの解明を行い、反応が表面でパターンを描きつつ広がりながら進むことを示唆する結果を得た。

研究成果

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• [文献書誌] H.Minoura: "Effects of Some Lewis Bases on CdX (X=S,Se) Photoelectrochemistry" Electrochemical Society Proceedinngs,(Photoelectrochemistry). 97-20. 199-208 (1997)
• [文献書誌] T.Yoshida: "Chemical Bath Deposition of Band Gap Tailored Indium Sulfide Thin Films" Electrochemical Society Proceedinngs,(Photoelectrochemistry). 92-20. 37-57 (1997)
• [文献書誌] K.Hayashi: "La_<0.5>Sr_<0.5>MnO_<3->YSZ Composite Film-Electrodes Prepared by Metal-Organic Decomposition for SOFC" The Proceedings of the Third International Symposium on Ionic and Mixed Conducting Ceramics. (in press).
• [文献書誌] S.Nakabayashi: "Reaction Pathway of 4 Electron oxidation of Formaldehyde on Platinum Electrode As Observed by In-Situ Optical Spectroscopy" Surf.Sci.386. 82-88 (1997)
• [文献書誌] I.Yagi: "In Situ Optical Second Harmonic Rotational Anisotropy Measurements of an Au(111) electrode during Electrodeposition of Tellurium" J.Phys.Chem.B. (in press).
• [文献書誌] I.Yagi: "Excitation Wavelength Dependent Three-Wave Mixing at a CO-Covedred Platinum Electrode" J.Phys.Chem.B. 101. 7414-7421 (1997)
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• [文献書誌] Y.NOSAKA: "Formation and Characterization of CdS Nanoparticles in Aqueous Solution,“Physics,Chemistry and Application of Nanostructures" World Scientific Publ., 8 (1997)