Effects of oxygen content on the microstructures and optical properties of thermochromic vanadium oxide thin films

Abstract

Reactive direct current magnetron sputtering and in situ thermal oxidation were used to prepare vanadium oxide (VO _X ) thin films with different oxygen contents. X-ray diffraction, Fourier transform infrared spectroscopy and a field emission scanning electron microscope were employed to characterize the films. The optical properties of the VO _X films at room temperature and 90 °C were investigated by applying an spectroscopic ellipsometer with a three-layer model of BEMA/Brendel–Bormann oscillator/substrate. It was demonstrated that the vanadium–oxygen bonds were strengthened, the film thickness and roughness decreased, while the grain size increased with increasing oxygen content. The increase in oxygen content had the effect of decreasing the near-infrared reflectance and free-electron concentration of the film at 90°C due to the decrease in the amount of VO₂.

Keywords:

• vanadium oxide thin film
• oxygen content
• microstructure
• optical property