Spontaneous epitaxy of VO and stabilization of interface phase of V₂O₃ during vanadium metal deposition on SrTiO₃ in vacuum

The deposition of vanadium metal on SrTiO₃ results in the spontaneous scavenging of oxygen ions from SrTiO₃ to oxidize vanadium to VO_x, where x = 0.5-1.2, depending on the temperature. At sufficiently high temperature, the VO_x forms as an epitaxial film on both SrTiO₃ (100) and SrTiO3₃ (111). Surprisingly, the oxygen scavenging and epitaxy persist for thicknesses over 300 Å with no sign of degradation. Additionally, when vanadium is deposited on SrTiO₃(111), an interfacial phase of hexagonal V₂O₃ with 2x2 surface reconstruction is formed, which is stable for three monolayers, before rocksalt VO(111) starts to be formed. We describe the growth process and layer by layer characterization of the films using in situ reflection high-energy electron diffraction (RHEED), x-ray and ultraviolet photoelectron spectroscopy (XPS and UPS), and reflective electron energy loss spectroscopy (REELS), as well as ex situ grazing incidence in-plane x-ray diffraction and cross-sectional scanning transmission electron microscopy.