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VO 2 displays a semiconducting to metallic (SMT) transition accessible near room temperature. This makes it one of the most sought after materials for electrical and optical switching. But this can be utilized only when the synthesis process yields phase pure VO 2 without other oxides of vanadium. Across the SMT, VO 2 exhibits difference crystal structures with a rich phase behavior of insulating monoclinic M1, M2 and T phases. The objective of this study is to synthesize phase pure VO 2 and to investigate its structural evolution and infrared switching during the transition. In this work, a rapid non-equilibrium process namely Solution Combustion Synthesis (SCS) was employed. The structural phase transition (SPT) of VO 2 nanostructures synthesized by SCS was investigated by in-situ temperature controlled XRD across the SMT. Gaussian curve fittings for measured XRD patterns revealed that competing phases of M1 and R significantly contribute to the observed pattern at every increase in temperature. The powders were further characterized by FTIR, DSC and DC electrical conductivity. These studies show that a sharp SMT was observed at 68–70 °C. Infrared transmittance experiments pinpointed the transition. Carrier density and mobility of VO 2 were calculated. This suggests that this VO 2 thus synthesized displays excellent phase transition behavior and can be utilized in optical and electrical switching. [ABSTRACT FROM AUTHOR]

Vanadium dioxide (VO 2) 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 VO 2 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 VO 2 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 VO 2. • Single phase VO2 was grown at different temperatures using MOCVD on Si substrates. • Morphology of the thin films changed with the growth temperature. • Surface studies by XPS showed the presence of V in V3+, V4+ and V5+ states. • For a particular growth temperature, ratio of V3+, V4+ and V5+ states is optimal. • Varying growth temperature gives a handle to tweak defects and also the transition. [ABSTRACT FROM AUTHOR]