Comparison of the optical responses of O-poor and O-rich thermochromic VOX films during semiconductor-to-metal transition
Zhenfei Luo, ,
Zhiming Wu, ,
Tao Wang,
Xiangdong Xu,
Weizhi Li,
Wei Li,
Yadong Jiang
School of Optoelectronic Information, State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China (UESTC), Chengdu 610054, China
Received 20 November 2011. Revised 11 March 2012. Accepted 30 April 2012. Available online 23 May 2012.
O-poor and O-rich thermochromic vanadium oxide (VOX) nanostructured thin films were prepared by applying reactive direct current magnetron sputtering and post-annealing in oxygen ambient. UV–visible spectrophotometer and spectroscopic ellipsometry were used to investigate the optical properties of films. It was found that, when the O-poor VOX thin film underwent semiconductor-to-metal transition, the values of optical conductivity and extinction coefficient in the visible region increased due to the existence of occupied band-gap states. This noticeable feature, however, was not observed for the O-rich film, which showed a similar optical behavior with the stoichiometric crystalline VO2 films reported in the literatures. Moreover, the O-poor VOX film exhibits consistent variations of transmission values in the visible/near-infrared region when it undergoes semiconductor-to-metal transition.
Highlights
► An optical absorption shoulder is found in the absorption coefficient plot of O-poor VOX film. ► Enhancement of optical conductivity is observed in the O-poor VOX film when it undergoes SMT. ► It is believed that the optical property of the O-poor film is related to occupied band-gap states.
