Terahertz and Metal-insulator Transition Properties of VO2 Film Grown on Sapphire Substrate with MBE

Abstract

High quality stoichiometric VO2 films were grown on single crystal sapphire substrates by molecular beam epitaxy (MBE), the film thicknesses were precisely controlled on the nanoscale ranging from 15 nm to 60 nm. For the optimized sample, a distinct reversible metal-insulator transition (MIT) with abrupt resistance change more than four orders of magnitude was observed, which was comparable to the ever reported result for high quality single crystal VO2. Especially, the optical properties in the terahertz (THz) frequency range were characterized with THz time-domain spectroscopy (THz-TDs) measurements for samples with various thicknesses, and the results indicate that the THz properties of VO2 film was significantly affected by the thickness. Therefore, the thickness should to be precisely controlled to obtain reproducible and reliable performance. The THz devices based on VO2 film may benefit significantly from these achievements.