Asymmetric response of electrical conductivity and V valence state to strain in cation-deficient SrVO ultrathin films based on absorption measurements at the V L- and L-edges.

The correlation between electronic properties and epitaxial strain in a cation-deficient system has rarely been investigated. Cation-deficient SrVO 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 SrVO films of different thicknesses capped with 4 u.c. (unit cell) SrTiO layers, showing the coexistence of V and V in thick films. A different correlation between V valence state and epitaxial strain is observed for SrVO ultrathin films, i.e. a variation in V valence state is only observed for tensile-strained films. SrVO 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 SrVO films will be beneficial for functional oxide electronic devices.