Hydrogen-Ti${}^{3+}$ Complex as a Possible Origin of Localized Electron Behavior in Hydrogen-Irradiated SrTiO${}_3$

Abstract

A recent muon spin rotation (${\mu }^{+}$SR) study on a paramagnetic defect complex formed upon implantation of ${\mu }^{+}$ pseudo-proton into SrTiO${}_3$ is reviewed with a specific focus on the relation with experimental signatures of coexisting delocalized and localized electrons in hydrogen-irradiated metallic SrTiO${}_3$ films. The paramagnetic defect complex, composed of interstitial ${\mu }^{+}$ and Ti${}^{3+}$ 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${}^{+}$-Ti${}^{3+}$ 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 SrTiO${}_3$ in electron-rich conditions.

12 pages, 5 figures, e-J. Surf. Sci. Nanotech. (2022), advance online publication

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