Hydrogen-Ti³⁺ Complex as a Possible Origin of Localized Electron Behavior in Hydrogen-Irradiated SrTiO₃

抄録

A recent muon spin rotation (μ⁺SR) study on a paramagnetic defect complex formed upon implantation of μ⁺ pseudo-proton into SrTiO₃ is reviewed with a specific focus on the relation with experimental signatures of coexisting delocalized and localized electrons in hydrogen-irradiated metallic SrTiO₃ films. The paramagnetic defect complex, composed of interstitial μ⁺ and Ti³⁺ small polaron, is characterized by a small dissociation energy of about 30 meV. Density functional theory (DFT) calculations in the generalized gradient approximation (GGA) + U scheme for a corresponding hydrogen defect complex reveal that a thermodynamic donor level associated with electron transfer from an H⁺—Ti³⁺ complex to the conduction band can form just below the conduction band minimum for realistic U values. These findings suggest that the coexistence of delocalized and localized electrons can be realized in hydrogen-irradiated SrTiO₃ in electron-rich conditions.