Elucidating mechanism of perfect wetting behavior of liquid indium on molybdenum oxide films

2020 Fiscal Year Final Research Report

• Project/Area Number: 19K23573
• Research Category: Grant-in-Aid for Research Activity Start-up
• Allocation Type: Multi-year Fund
• Review Section: 0401:Materials engineering, chemical engineering, and related fields
• Research Institution: Kyoto University
• Principal Investigator: Katsube Ryoji 京都大学, 工学研究科, 助教 (10839947)
• Project Period (FY): 2019-08-30 – 2021-03-31
• Keywords: 界面反応 / 濡れ性 / 化学熱力学 / 化合物半導体 / 薄膜太陽電池 / 液体金属

Outline of Final Research Achievements

Liquid indium (In) shows perfect wetting behavior on molybdenum oxide (MoOx) films despite of the fact that liquid metals generally tend to form droplets because of large surface tension. This study aims to reveal the wetting mechanism of this unique liquid-metal/oxide system.
We investigated the wetting behaviors of liquid In on the MoOx films with various oxygen content, x. As a result, we revealed that perfect wetting occurs when x is close to 3. We also detected the formation of (111)-oriented indium oxide (In2O3) at the interface between In and MoOx in the case where MoOx is perfectly wetted by liquid In. Furthermore, we found that liquid In shows dewetting on amorphous In2O3 films. According to the above results, we conclude that the key factor of the perfect wetting phenomenon in In/MoOx system is the formation of (111)-oriented In2O3 through chemical reaction at the interface.

Free Research Field

材料工学

Academic Significance and Societal Importance of the Research Achievements

金属の濡れ現象は，凝固・鋳造や化合物半導体の製膜等の材料工学における幅広いプロセスにおいて重要である。液体金属が酸化物の表面を完全に濡らす液体In/MoOx系は稀有な例に過ぎなかったが，本研究によってそのメカニズムが明らかとなり，Inだけでなく様々な金属が完全濡れ状態となるような固体表面の探索指針が得られた。従って本研究の成果は，着想の端緒となった光・電子材料りん化インジウム(InP)の任意基板上製膜のように，完全濡れ状態にある液体金属を利用した次世代のデバイス・材料設計へと発展し得る。