Strain-Assisted Topochemical Synthesis of La-Doped SrVO₂H Films

Abstract

Perovskite oxyhydride SrVO₂H (V³⁺, d²) is a Mott insulator with a strong two-dimensional correlation due to anion ordering. In this study, we attempted electron doping by aliovalent substitution. Although Sr₁–xLaxVO₃ thin films (x ≤ 0.4) on a SrTiO₃ substrate were topochemically reduced using CaH₂, vanadium of the reduced films retained the trivalent state. Combined with the results of secondary ion mass spectroscopy, we conclude that Sr₁–xLaxVO₂+xH₁–x is obtained, where the apical oxygen site is partially replaced by hydride anions. First-principles theoretical calculations highlight the role played by compressive biaxial strain in stabilizing the charge-compensated Sr₁–xLaxVO₂+xH₁–x phase, rather than the electron-doped Sr₁–xLaxVO₂H. The present study demonstrates that topochemical reactions combined with substrate strain provide various opportunities to widen the compositional space in mixed-anion compounds.