MOCVD growth and characterization of vanadium dioxide films

High-quality vanadium dioxide (VO2) films were synthesized on sapphire and silicon substrates by metal–organic chemical vapor deposition. Optimal growth conditions for obtaining abrupt and reversible semiconductor–metal phase transition of VO2 were found. X-ray diffraction, Raman scattering spectroscopy, and scanning electron microscopy measurements suggested that grown VO2 films have high crystal quality. It was shown that, at a fixed proportion between the rates of the oxygen and argon flows in the reactor and at a substrate temperature in the range of 440 ≤ T ≤ 470 °C, the monoclinic phase of VO2 formed in the deposited films. The films grown on sapphire and silicon substrates were found to have an underlying conducting transition layer forming ohmic back contact to VO2 film. The presence of such back contact layer has allowed us to form VO2-based vertical devices. In such structures, VO2 films have shown conductivity changes up to four orders of magnitude due to the phase transition. This demonstrates the high quality of grown films without post-deposition annealing.