Defect engineering of VO2 thin films synthesized by Chemical Vapor Deposition

Abstract

Vanadium dioxide (VO2) has been a much sought after candidate for many electronics and photonics based applications. These applications demand CMOS compatibility and simple but scalable synthesis procedure. Herein we report the deposition of VO2 on CMOS compatible Si substrates via easily scalable Metal Organic Chemical Vapor Deposition (MOCVD) at different substrate temperatures between 520 and 550 °C. The morphology of the films deposited at different growth temperatures varied drastically despite retaining VO2 in the M1 phase. This was verified by XRD and Raman experiments. The thin films deposited at 535 °C showed sharp grain boundaries with a grain size of about 200 nm. Similarly, the electrical characteristics of the films deposited at 535 °C showed superior transition compared to the films deposited at other temperatures. However the films deposited at 550 °C retained the superiority in the transition strength, the transition width and the hysteresis of the transition increased at that temperatures. We understand that the reason for this observed behavior is the fraction of surface defects. It is seen from XPS measurements that vanadium was available in V3+, V4+ and V5+ oxidation states and the fractions of these individual components varied in all the thin films deposited at different temperatures. We believe that the defects fraction can give a handle to control the nature and quality of the transition in VO2.