Thermal transition behaviors of vanadium pentoxide film during post-deposition annealing

Abstract

Vanadium pentoxide (V2O5) films were deposited on sapphire substrates by radio frequency (R.F.) magnetron sputtering at 450 °C and annealed in various ambient atmospheres. The influence of ambient atmospheres on the structure, optical properties, and morphology of the thin films after annealing were characterized, and the transition behaviors in the annealing process were investigated by DSC, temperature-dependent Raman and FTIR. The results demonstrated that V2O5 films underwent four different transition behaviors during post-deposition annealing due to the different oxygen proportion of ambient. Different products (VO2(B), VO2(R)) in the transition process were the main reason for the evolution of optical properties. No transition behaviors occurred because of the oxygen-rich ambient when annealed in air, and no significant change in infrared transmittance was observed. When annealed in 0.1% O2/Ar, the film was converted to VO2(B) with the decrease of infrared transmittance. In the case of 0.01% O2/Ar, metastable VO2(B) and VO2(R) were observed as intermediate crystalline phases before V2O5 finally transformed to VO2(M), and the changes in the three stages of two drops and one rise were shown in infrared transmittance. While annealed in pure argon ambient, V2O5 was turned into VO2 (R) and VO2 (M) without VO2 (B) phase production, accompanied by a single change of infrared transmittance reduction and recovery. This provides a more detailed vanadium oxide thermal transition process and shows data reference for the preparation technology and application of vanadium oxide materials.