Spectral assignments in the infrared absorption region and anomalous thermal hysteresis in the interband electronic transition of vanadium dioxide films

Abstract

The metal–insulator transition (MIT) is of key importance for understanding the fundamental electronic interaction that determines the physical properties of vanadium dioxide (VO₂) film. Here, the spectral slopes of transmittance and reflectance in the infrared absorption region (about 0.62–1.63 eV) and the interband electronic transitions for VO₂ films with thicknesses of 27, 40 and 63 nm have been investigated. The potential applications of the spectral slopes were presented in detail. It is found that the variation of resistivity and transmittance increases with the spectral slopes of transmittance and reflectance. It is surprising that the resistivity of the VO₂ film with a thickness of 27 nm is larger than that of the VO₂ film with a thickness of 40 nm in the metal state. In addition, an anomalous counterclockwise thermal hysteresis with higher energy from the interband electronic transition was also found during the MIT process for the thinnest film. It is believed that this remarkable phenomenon could be related to the correlation effects in the rutile phase, which could lead to the splitting of the a_1g band into Hubbard bands. The lower Hubbard band would result in an electronic transition blue-shift with the empty e^σ_g band, which can explain the origin of the counterclockwise thermal hysteresis and the abnormal resistivity in the metal state.