Reactive RF Sputtering of VO2

Abstract

There are multiple oxides that exhibit metal-to-insulator transition, VO2 is one of them. What makes it unique is that the transition occurs at near room temperature, thereby making the energy cost of switching very low. The material had amassed a large amount of attention from scientific community over the past few years, resulting in low power devices like phase change field-effect transistors with switching times on the order of picoseconds. The deposition of VO2 can be approached via chemical vapour deposition, evaporation, sputtering, or sol-gel. The focus of my work was the reactive RF sputtering approach to depositing polycrystalline VO2 thin films. The optimal deposition parameters were demonstrated to be 500 degC substrate temperature and 10.2%-10.3% partial oxygen flow using a 2'' target at 200W RF power. Resulting growth rate was about 1.5 nm/min. The quality of VO2 was studied using device level S-parameter measurements of insertion loss using vector network analyzer while changing temperature from 25 degC to 100 degC. Future plans for further improvement of the material deposited and solutions for localized heating using wave-shaped Au/Cr micro-heaters are provided.