Enhanced Metal–Insulator Transition Performance in Scalable Vanadium Dioxide Thin Films Prepared Using a Moisture-Assisted Chemical Solution Approach

Vanadium dioxide (VO₂) is a strong-correlated metal–oxide with a sharp metal–insulator transition (MIT) for a range of applications. However, synthesizing epitaxial VO₂ films with desired properties has been a challenge because of the difficulty in controlling the oxygen stoichiometry of VO_<i>x</i>, where <i>x</i> can be in the range of 1 < <i>x</i> < 2.5 and V has multiple valence states. Herein, a unique moisture-assisted chemical solution approach has been developed to successfully manipulate the oxygen stoichiometry, to significantly broaden the growth window, and to significantly enhance the MIT performance of VO₂ films. The obvious broadening of the growth window of stoichiometric VO₂ thin films, from 4 to 36 °C, is ascribed to a self-adjusted process for oxygen partial pressure at different temperatures by introducing moisture. A resistance change as large as 4 orders of magnitude has been achieved in VO₂ thin films with a sharp transition width of less than 1 °C. The much enhanced MIT properties can be attributed to the higher and more uniform oxygen stoichiometry. This technique is not only scientifically interesting but also technologically important for fabricating wafer-scaled VO₂ films with uniform properties for practical device applications