Continuous Tuning of Phase Transition Temperature in VO₂ Thin Films on c-Cut Sapphire Substrates via Strain Variation

Vanadium dioxide (VO 2 ) 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 VO 2 lattice is found to be dependent on the VO 2 thickness and the VO 2 /AZO interface roughness. The semiconductor-to-metal transition (SMT) properties of VO 2 thin films are characterized and the transition temperature ( T c ) is successfully tuned by the VO 2 thickness as well as the VO 2 /AZO interface roughness. It shows that the T c of VO 2 decreases with the decrease of film thickness or VO 2 /AZO interface roughness. Other SMT properties of the VO 2 films are maintained during the T c tuning. The results suggest that the strain tuning induced by AZO buffer provides an effective approach for tuning T c of VO 2 continuously.