Simple sol-gel process and one-step annealing of vanadium dioxide thin films: Synthesis and thermochromic properties

摘要

A simple and cost effective sol-gel process for producing vanadium dioxide thin films was developed via thermolysis of V_2O_5-nH_2O (n≈2) V~v precursors prepared by dissolving vanadium powder or V_2O_5 powder in 30% hydrogen peroxide solutions. After spin-coating on fused silica substrates and annealing at 750 ℃ in vacuum, without any intermediate gas reducing step, the major phase VO_2(M, monoclinic phase) was found in both of the films based on V-H_2O_2 and V_2O_5-H_2O_2 precursor, exhibiting large transmittance changes (>40%) in the IR region (>2000 nm) and small hysteresis loop width (<5 ℃) which were comparable to reported epitaxial VO_2 films. The two films have similar metal-to-insulator transition temperature rc = 62.5 °C, lower than the classical value of 68℃ for VO_2 thin films. In addition, the method enables simple doping, as found for 0.56 at% W-doped VO_2 films. This intrinsically simple solution process followed by one-step annealing makes it potentially useful in smart window applications.