Substrate-induced disorder in V ₂O ₃ thin films grown on annealed c-plane sapphire substrates

We investigate the structural and electronic properties of V 2O 3 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 V 2O 3'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 V 2O 3's strongly correlated metallic phase to crystalline defects and structural disorder. © 2012 American Institute of Physics.