Tuning metal-insulator transitions in epitaxial V₂O₃ thin films

We present a study of the synthesis of epitaxial V$_2$O$_3$ films on $c$-plane Al$_2$O$_3$ substrates by reactive dc-magnetron sputtering. The results reveal a temperature window, at substantially lower values than previously reported, wherein epitaxial films can be obtained when deposited on [0001] oriented surfaces. The films display a metal-insulator transition with a change in resistance of up to four orders of magnitude, strongly dependent on the O$_2$ partial pressure during deposition. While the electronic properties of the films show sensitivity to the amount of O$_2$ present during deposition of the films, their crystallographic structure and surface morphology of atomically flat terraced structures with up to micrometer dimensions are maintained. The transition temperature, as well as the scale of the metal-insulator transition, is correlated to the stoichiometry and local strain in the films controllable by the deposition parameters.