Structural and electronic properties ofn-doped andp-dopedSrTiO3

We study the effects of $n$-doping and $p$-doping on the structural and electronic properties of $\mathrm{Sr}\mathrm{Ti}{\mathrm{O}}_3$ using the ab initio pseudopotential density functional theory. Two types of electron doping and one type of hole doping are considered: introducing O vacancies, substituting V for Ti, and substituting Sc for Ti. We find that all dopings lead to small structural distortions. The effect of O vacancies on the structure is the largest. Electron doping leads to significant changes of the conduction band. For the O vacancy case, there is a Ti $3d\text{−}{e}_g$ type defect state near the lower conduction band; while in the case of substitutional V, some parts of the lowest conduction bands become very flat. Hole doping yields a larger density of states at the Fermi level than electron doping. Our results indicate that the rigid band model with a Fermi level shift upwards or downwards is not applicable to describe the effects of oxygen vacancy induced electron doping on the electronic properties; however, this may be a reasonable approximation for the case of hole doping. Finally, we estimate the electron-phonon coupling parameters and discuss the implications of this study on superconductivity in the $\mathrm{Sr}\mathrm{Ti}{\mathrm{O}}_3$ system.