The correlation between electronic properties and epitaxial strain in a cation-deficient system has rarely been investigated. Cation-deficient SrVO3 films are taken as a model system to investigate the strain-dependent electrical and electronic properties. Using element- and charge-sensitive soft X-ray absorption, V L-edge absorption measurements have been performed for Sr1-yVO3 films of different thicknesses capped with 4 u.c. (unit cell) SrTiO3 layers, showing the coexistence of V4+ and V5+ in thick films. A different correlation between V valence state and epitaxial strain is observed for Sr1-yVO3 ultrathin films, i.e. a variation in V valence state is only observed for tensile-strained films. Sr1-yVO3 thin films are metallic and exhibit a thickness-driven metal-insulator transition at different critical thicknesses for tensile and compressive strains. The asymmetric response of electrical conductivity to strain observed in cation-deficient Sr1-yVO3 films will be beneficial for functional oxide electronic devices.
Keywords: 3d transition metal oxides; soft X-ray absorption measurements; thickness-dependent properties; thin-film engineering.