Origin of Oxygen Partial Pressure-Dependent Conductivity in SrTiO3

TL;DR

This study uses first-principles calculations to clarify how intrinsic defects in SrTiO3 influence its conductivity under different oxygen partial pressures, resolving longstanding questions about its variable electronic behavior.

Contribution

It systematically identifies dominant intrinsic defects and their roles in tuning SrTiO3's conductivity across varying oxygen chemical potentials.

Findings

VO acts as a donor under O-poor conditions.

VSr functions as an acceptor in oxygen-deficient environments.

TiSr becomes a significant donor under oxygen-rich conditions.

Abstract

SrTiO3 (STO) displays a broad spectrum of physical properties, including superconductivity, ferroelectricity, and photoconductivity, making it a standout semiconductor material. Despite extensive researches, the oxygen partial pressure-dependent conductivity in STO has re-mained elusive. This study leverages first-principles calculations, and systematically investigates the intrinsic defect properties of STO. The results reveal that VO, VSr, and TiSr are the dominant intrinsic defects, influencing STO's conductivity under varying O chemical potentials (oxygen partial pressures). Under O-poor condition, VO is the predominant donor, while VSr is the main acceptor. As the oxygen pressure increases, TiSr emerges as a critical donor defect under O-rich condition, significantly affecting conductivity. Additionally, the study elucidates the abnormal phenomenon where VTi, typically an acceptor, exhibits donor-like behavior due to the formation of O-trimer. This work offers a comprehensive understanding of how intrinsic defects tune the Fermi level, thereby altering STO's conductivity from metallic to n-type, and eventually to p-type across different O chemical potentials. These insights resolve the long-standing issue of oxygen partial pressure-dependent conductivity and explain the observed metallic conductivity in oxygen-deficient STO.