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

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.