Continuous Tuning of Phase Transition Temperature in VO2Thin Films on c-Cut Sapphire Substrates via Strain Variation

Vanadium dioxide (VO2) thin films with controlled thicknesses are deposited on c-cut sapphire substrates with Al-doped ZnO (AZO) buffer layers by pulsed laser deposition. The surface roughness of AZO buffer layers is varied by controlling oxygen pressure during growth. The strain in the VO2lattice is found to be dependent on the VO2thickness and the VO2/AZO interface roughness. The semiconductor-to-metal transition (SMT) properties of VO2thin films are characterized and the transition temperature (Tc) is successfully tuned by the VO2thickness as well as the VO2/AZO interface roughness. It shows that the Tcof VO2decreases with the decrease of film thickness or VO2/AZO interface roughness. Other SMT properties of the VO2films are maintained during the Tctuning. The results suggest that the strain tuning induced by AZO buffer provides an effective approach for tuning Tcof VO2continuously.