Complicated point defects in monolayer Ga2S3: stability, midgap states and magnetism

Abstract

Motivated by recent experimental realization of single-layer α-Ga2S3 [Zheng et al., Adv. Funct. Mater. 31, 2008307(2021)], by using first principles calculations, we systematically investigated the structural, electronic and magnetic properties of single-layer α-Ga2S3 with intrinsic point defects. Although it is a binary semiconductor, its point defects properties are complicated, since there are nonequivalent Ga and S atomic sites in this compound. The most energetically stable vacancy and interstitial defect are VS2 and Si1 for the entire sulfur chemical potential range, while the most energetically favorable antisite defect is dependent on the sulfur chemical potential, such as GaS2 under S-poor condition and SGa1 (SGa2) under S-rich condition. The sulfur vacancy defects (VS1, VS2 and VS2) have induced spin-degenerated defect states in the band gap or the valence band edge, while the gallium vacancy defects (VGa1, and VGa2) have spin-polarized defect states in the band gap or valence band edge with the magnetic moment of 1.30 μB and 1.21μB per defect. The interstitial defects (Gai1, Si1 and Si2) can generate spin-degenerated in-gap defect states. The antisite defects (GaS1, GaS2, GaS3, SGa1, and SGa2) have spin-polarized in-gap defect states with weak magnetic moments of 0.70 μB, 0.69μB, 0.64μB, 0.66μB and 0.65μB per defect. Besides, the origin of the defect states and magnetic moments are examined in detail. These findings are helpful for understanding the defect properties of two dimensional IIIA-VIA binary chalcogenide Ga2S3 and improving its technological applications.