Effect of Post Growth Annealing on Phase Transition Parameters in LP CVD Grown Vanadium Dioxide Thin Films

Vanadium dioxide VO2 is a promising functional material for many practical applications, due to its large jump in conductivity observed during the phase transition. One of the main tasks for VO2 material is to improve its phase transition characteristics. In this paper, we study the effect of post growth annealing on the phase transition properties in two types of VO2 films synthesized by LP CVD on $\mathrm {S}\mathrm {i}O_{2}/\mathrm {S}\mathrm {i}$ substrates: with a low $(< 10)$ and high $(>10^{3})$ resistance ratio during the phase transition. Using layer-by-layer etching, we showed that both types of VO2 films are not uniform in thickness due to the presence of a non-stoichiometric $VO_{2-\mathrm {x}}$ layer. The location of this layer determines the experimentally measured value of the jump in the conductivity of VO2 films, as well as the possibility of improving the phase transition characteristics in the films by annealing. As a result, we found annealing conditions that increase the value of the jump in resistance during a phase transition up to 700 times. The results of this work are promising both for using VO2 as the basis for novel electrical and optical micro- and nanodevices, and for studying the physicochemical properties of VO2 films synthesized by CVD.