Formation energies of intrinsic point defects in monoclinic VO2 studied by first-principles calculations

Yuanyuan Cui,Lanli Chen,Yanfeng Gao,Hongjie Luo,Bin Liu

doi:10.1063/1.4964495

Abstract

VO2 is an attractive candidate for intelligent windows and thermal sensors. There are challenges for developing VO2-based devices, since the properties of monoclinic VO2 are very sensitive to its intrinsic point defects. In this work, the formation energies of the intrinsic point defects in monoclinic VO2 were studied through the first-principles calculations. Vacancies, interstitials, as well as antisites at various charge states were taken into consideration, and the finite-size supercell correction scheme was adopted as the charge correction scheme. Our calculation results show that the oxygen interstitial and oxygen vacancy are the most abundant intrinsic defects in the oxygen rich and oxygen deficient condition, respectively, indicating a consistency with the experimental results. The calculation results suggest that the oxygen interstitial or oxygen vacancy is correlated with the charge localization, which can introduce holes or electrons as free carriers and subsequently narrow the band gap of monoclinic VO2. These calculations and interpretations concerning the intrinsic point defects would be helpful for developing VO2-based devices through defect modifications.

Highlights

Vanadium dioxide (VO2) is an interesting material because of the metal to insulator transition (MIT) around 67 ◦C, which is coupled with the reversible structural transition from the rutile phase at a high temperature to the monoclinic phase at a low temperature.[1]
The finite-size supercell correction scheme was adopted as the charge correction scheme
The calculation results show that the oxygen interstitial is the dominant intrinsic defect under oxygen-rich condition, while under oxygen-poor condition, the oxygen vacancy becomes the dominant intrinsic defect in VO2(M)

Summary

Introduction

Vanadium dioxide (VO2) is an interesting material because of the metal to insulator transition (MIT) around 67 ◦C, which is coupled with the reversible structural transition from the rutile phase at a high temperature to the monoclinic phase at a low temperature.[1]. The explicit kinds of intrinsic defects introduced by the deficient or excess oxygen concentration are still open issues.[10,11,12] Some authors suggest that the oxygen or vanadium excess is the reason for the vanadium or oxygen vacancies, while others propose that the corresponding defects are oxygen or vanadium interstitials.[10,11,12] It is of special interest to study the intrinsic point defects in VO2(M) under excess or deficient oxygen conditions, which would provide useful guidance to the fabrication of high quality VO2 films

Methods

Results

Conclusion