Effect of annealing temperature on the structure and properties of vanadium oxide films

Abstract

Vanadium oxide is a promising material due to its thermochromic characteristics and is currently being evaluated for use in various thermal and optical applications. VO2 films were prepared on quartz substrates using the sol-gel method, spin coating, and annealing. To obtain VO2 films with high purity and improve their thermochromic properties, the effect of the annealing temperature on the film’s structure and properties was investigated. As the annealing temperature increased from 450 °C to 650 °C, the film’s phase component went through an amorphous phase, a VO2 phase with initial crystallization, a VO2 phase with high purity and mature crystallization, a VO2 phase with a small amount of a V2O5 phase, and a VO2 phase with a greater amount of a V2O5 phase. The film’s crystallinity improved continuously, and the film annealed at 550 °C was composed of fine, compact particles; higher temperatures resulted in coarser grains. The maximum transmittance mutation of the film to infrared radiation first increased and then decreased. The film annealed at 550 °C attained the maximum value of 67% at a wavelength of 2500 nm, and its phase transition temperature was 67.6 °C.