Local geometric and electronic structures of gasochromic VOx filmsElectronic supplementary information (ESI) available. See DOI: 10.1039/c3cp54773f

• Main Authors: Jang, Wei-Luen, Lu, Yang-Ming, Chen, Chi-Liang, Lu, Ying-Rui, Dong, Chung-Li, Hsieh, Ping-Hung, Hwang, Weng-Sing, Chen, Jeng-Lung, Chen, Jin-Ming, Chan, Ting-Shan, Lee, Jyh-Fu, Chou, Wu-Ching
• Format: Journal Article
• Language: English
• Published: 12.02.2014
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/c3cp54773f

VO x films were deposited by radio-frequency reactive magnetron sputtering from a vanadium target at room temperature. Local atomic and electronic structures of the films were then modified by thermal annealing. The oxidation state and structural and gasochromic properties of the films were elucidated by X-ray absorption spectroscopy. Analytical results indicate that the as-deposited VO x films were amorphous with mixed V 4+ and V 5+ valences. The amorphous VO x had a disordered and expanded lamellar structure resembling that of polymer-intercalated V 2 O 5 gels. VO x films were crystallized into orthorhombic V 2 O 5 at 300 °C, and the lamellar structure was eliminated at 400 °C. Additionally, the gasochromic reaction reduced the vanadium valence via intervalence transitions between V 5+ and V 3+ . Moreover, removing the lamellar structure reduced the gasochromic rate, and the gasochromic reaction transformed the V 2 O 5 crystalline phase irreversibly into an H 1.43 V 2 O 5 phase. Based on the results of this study, amorphous VO x with a lamellar structure is recommended for use in H 2 gas sensors. This study investigates the local geometric and electronic structures of gasochromic VO x films by X-ray absorption spectroscopy.