| Summary: | Vanadium oxide (VO<sub>2</sub>) is considered a Peierls–Mott insulator with a metal–insulator transition (MIT) at T<sub>c</sub> = 68° C. The tuning of MIT parameters is a crucial point to use VO<sub>2</sub> within thermoelectric, electrochromic, or thermochromic applications. In this study, the effect of oxygen deficiencies, strain engineering, and metal tungsten doping are combined to tune the MIT with a low phase transition of 20 °C in the air without capsulation. Narrow hysteresis phase transition devices based on multilayer VO<sub>2</sub>, WO<sub>3</sub>, Mo<sub>0.2</sub>W<sub>0.8</sub>O<sub>3,</sub> and/or MoO<sub>3</sub> oxide thin films deposited through a high vacuum sputtering are investigated. The deposited films are structurally, chemically, electrically, and optically characterized. Different conductivity behaviour was observed, with the highest value towards VO<sub>1.75</sub>/WO<sub>2.94</sub> and the lowest VO<sub>1.75</sub> on FTO glass. VO<sub>1.75</sub>/WO<sub>2.94</sub> showed a narrow hysteresis curve with a single-phase transition. Thanks to the role of oxygen vacancies, the MIT temperature decreased to 35 °C, while the lowest value (T<sub>c</sub> = 20 °C) was reached with Mo<sub>0.2</sub>W<sub>0.8</sub>O<sub>3</sub>/VO<sub>2</sub>/MoO<sub>3</sub> structure. In this former sample, Mo<sub>0.2</sub>W<sub>0.8</sub>O<sub>3</sub> was used for the first time as an anti-reflective and anti-oxidative layer. The results showed that the MoO<sub>3</sub> bottom layer is more suitable than WO<sub>3</sub> to enhance the electrical properties of VO<sub>2</sub> thin films. This work is applied to fast phase transition devices.
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