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

Abstract

A simple and cost effective sol–gel process for producing vanadium dioxide thin films was developed via thermolysis of V2O5·nH2O (n≈2) VV precursors prepared by dissolving vanadium powder or V2O5 powder in 30% hydrogen peroxide solutions. After spin-coating on fused silica substrates and annealing at 750°C in vacuum, without any intermediate gas reducing step, the major phase VO2(M, monoclinic phase) was found in both of the films based on V–H2O2 and V2O5–H2O2 precursor, exhibiting large transmittance changes (>40%) in the IR region (>2000nm) and small hysteresis loop width (<5°C) which were comparable to reported epitaxial VO2 films. The two films have similar metal-to-insulator transition temperature τC=62.5°C, lower than the classical value of 68°C for VO2 thin films. In addition, the method enables simple doping, as found for 0.56at.% W-doped VO2 films. This intrinsically simple solution process followed by one-step annealing makes it potentially useful in smart window applications.