Development of super multilayer oxide films with ruitle structure by spinodal decomposition toward high power solar cell

2019 Fiscal Year Final Research Report

• Project/Area Number: 17K06794
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Inorganic materials/Physical properties
• Research Institution: Okayama University
• Principal Investigator: Muraoka Yuji 岡山大学, 異分野基礎科学研究所, 准教授 (10323635)
• Project Period (FY): 2017-04-01 – 2020-03-31
• Keywords: スピノーダル分解 / ルチル型酸化物 / ラメラ周期 / 異原子価イオンドープ / 超多層構造膜 / 歪効果

Outline of Final Research Achievements

The anisotropy in the spinodal decomposition of a rutile-type TiO2-VO2 system has been studied in the form of bulk and film. In the bulk, the periodicity of lamella structures formed by decomposition along the c-axis direction and the kinetics of the decomposition are investigated. Consequently, it is found that the lamella period increases from 26 to 48 nm with the annealing time, and that the phase separation is promoted by a small amount of Al3 + ion doping while suppressed by Nb5 + doping. In the films, we apply the anisotropy in decomposition to the formation of multilayer structures in TiO2-VO2 films. By changing the orientation of the TiO2-VO2 films, we succeeded in forming multilayer film in which the lamella structure is arranged horizontally, diagonally, and vertically with respect to the surface of the substrate. It is also revealed that strain relaxation in the c-axis length of the film is crucial for enabling the spinodal decomposition in TiO2-VO2 films.

Free Research Field

固体化学

Academic Significance and Societal Importance of the Research Achievements

酸化物系でスピノーダル分解を起こす物質例は5－6件に限られる。異方的に起こる例は、本系以外にルチル型のTiO2-SnO2とコランダム型のAl2O3-Cr2O3の2例が知られているのみである。そのため、本系で得られる周期構造や分解速さの知見は、酸化物系スピノーダル分解の進行や分解方向のメカニズムを理解する重要な情報になる。また、本研究は、スピノーダル分解が酸化物の多層膜作製のための有効な手段になることを明示した。これによりこれまで困難であった超多層構造膜における物性・機能の研究が可能となった。スピノーダル分解を用いた多層化技術により今後、超多数界面による高出力太陽電池材料の開発に期待がもたれる。