Intrinsic Defects and Electronic Conductivity of TaON: First-Principles Insights

TL;DR

This study uses first-principles calculations to analyze the defect properties and electronic conductivity of TaON, revealing its dominant antisite defect, doping challenges, and conditions for stable synthesis, which are crucial for its application as a photocatalyst.

Contribution

It provides new insights into the defect mechanisms and electronic properties of TaON, highlighting the role of antisite defects and synthesis conditions for improved photocatalytic performance.

Findings

O_N antisite is the dominant defect in TaON.

O_N antisite has a shallower donor level than vacancies.

TaON's electronic conductivity is enhanced by the delocalized Ta 5d orbitals.

Abstract

As a compound in between the tantalum oxide and nitride, the tantalum oxynitride TaON is expected to combine their advantages and act as an efficient visible-light-driven photocatalyst. In this letter, using hybrid functional calculations we show that TaON has different defect properties from the binary tantalum oxide and nitride: (i) instead of O or N vacancies or Ta interstitials, the $O_N$ antisite is the dominant defect, which determines its intrinsic n-type conductivity and the p-type doping difficulty; (ii) the $O_N$ antisite has a shallower donor level than O or N vacancies, with a delocalized distribution composed mainly of the Ta $5d$ orbitals, which gives rise to better electronic conductivity in the oxynitride than in the oxide and nitride. The phase stability analysis reveals that the easy oxidation of TaON is inevitable under O rich conditions, and a relatively O poor condition is required to synthesize stoichiometric TaON samples.