Epitaxial growth and electronic structure of oxyhydride SrVO₂H thin films

Oxyhydride SrVO₂H epitaxial thin films were fabricated on SrTiO₃ substrates via topotactic hydridation of oxide SrVO₃ films using CaH₂. Structural and composition analyses suggested that the SrVO₂H film possessed one-dimensionally ordered V-H⁻-V bonds along the out-of-plane direction. The synthesis temperature could be lowered by reducing the film thickness, and the SrVO₂H film was reversible to SrVO₃ by oxidation through annealing in air. Photoemission and X-ray absorption spectroscopy measurements revealed the V³⁺ valence state in the SrVO₂H film, indicating that the hydrogen existed as hydride. Furthermore, the electronic density of states was highly suppressed at the Fermi energy, consistent with the prediction that tetragonal distortion induces metal to insulation transition.