Mechanistic insights on the electronic properties and electronic/atomic structure aspects in orthorhombic SrVO3 thin films: XANES–EXAFS study

Abstract

Correlations among the B–O6 octahedra distortions, existing polymorphous phases, band structures and electronic conductivities of ABO₃ perovskites are matters for debate and require a deep understanding of their local atomic/electronic structures and diverse assets. In this study, to illustrate the distortion in V–O6 octahedra and its implication on the band structure and electronic properties, spectroscopic investigations on the RF-sputtering grown insulating SrVO₃ thin films were employed using X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS). V K-edge and V L_3,2-edge XANES, along with atomic multiplet calculations, have confirmed the 4+ oxidation state of V ions in the pristine and annealed SrVO₃ thin films. Lower t_2g/e_g peak intensity ratio and smaller energy separation between t_2g and e_g peaks in the O K-edge XANES spectra, compared to the VO₂ reference sample, have confirmed a larger V–O6 distortion in the orthorhombic SrVO₃ thin films. Moreover, from the EXAFS data analysis, the local orthorhombic structure has been identified in the pristine and annealed SrVO₃ thin films, compelling significant distortion in the V–O6 octahedra. Dimerization in the vanadium chains and V–V twisting, caused by V–O6 octahedra distortion, manifests a miscellaneous ligand field interaction between O 2p and V 3d orbitals and facilitates (i) a larger separation between the bonding and antibonding d_‖ orbitals and (ii) an upward shift of the π* band in the band structure, leading to larger band gaps in the insulating SrVO₃ thin films. Our spectroscopy results may open up new avenues for the mechanism of insulating/conducting character in other complicated perovskite materials using XANES–EXAFS.