Substrate-induced disorder in V₂O₃thin films grown on annealed<i>c</i>-plane sapphire substrates

Abstract

We investigate the structural and electronic properties of V2O3 thin films deposited by oxygen plasma-assisted molecular beam epitaxy onto annealed and unannealed c-plane sapphire substrates. Annealing the substrates before growth to produce ultra-smooth surfaces improved initial epitaxy, according to in situ reflection high-energy electron diffraction. Surprisingly, films deposited on annealed substrates had a more island-like surface, broader x-ray diffraction peaks, and an increased resistivity of V2O3’s normally metallic high-temperature phase. We attribute these results to enhanced strain coupling at the interface between the substrate and film, highlighting the vulnerability of V2O3’s strongly correlated metallic phase to crystalline defects and structural disorder.