Theory of dopants and defects in Co-doped TiO2 anatase

TL;DR

This paper uses first-principles calculations to analyze how Co dopants and native defects influence the electrical and magnetic properties of TiO2 anatase, aligning predictions with experimental observations.

Contribution

It provides a detailed microscopic understanding of defect formation, magnetic moments, and carrier concentrations in Co-doped TiO2 anatase through first-principles calculations.

Findings

Co dopants can occupy interstitial sites acting as donors.

Native defects and Co doping lead to n-type conductivity.

Predicted magnetic moments and carrier concentrations match experiments.

Abstract

We report first-principles microscopic calculations of the formation energy, electrical activity, and magnetic moment of Co dopants and a variety of native defects in TiO2 anatase. Using these results, we use equilibrium thermodynamics to predict the resulting carrier concentration, the average magnetic moment per Co, and the dominant oxidation state of Co. The predicted values are in good agreement with experiment under the assumption of O-poor growth conditions. In this regime, a substantial fraction of Co dopants occupy interstitial sites as donors. The incomplete compensation of these donors by substitutional Co acceptors then leads to n-type behavior, as observed experimentally.