Atypical behavior of intrinsic defects and promising dopants in two-dimensional <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mrow><mml:mi>WS</mml:mi></mml:mrow><mml:mn>2</mml:mn></mml:msub></mml:math>
Akash Singh, Abhishek K. Singh
Abstract
The $2\mathrm{D}\text{\ensuremath{-}}\mathrm{W}{\mathrm{S}}_{2}$ is an emerging material for next-generation electronic and optoelectronic devices. These applications are very sensitive and can be adversely affected by defects incorporated during the sample growth. Using hybrid density functional approach, we carried out a comprehensive study on intrinsic and extrinsic defects in $2\mathrm{D}\text{\ensuremath{-}}\mathrm{W}{\mathrm{S}}_{2}$. All the intrinsic defects and their complexes are found to be deep and self-compensating. S vacancy $({\mathrm{V}}_{\text{S}})$, which has been previously attributed as the source of $n$-type conductivity, turns out to be an electron trap center. We found that ${\mathrm{V}}_{\text{S}}$ gives rise to a suboptical gap, which can be the source of single-photon emitters. Interestingly, hydrogen interstitial $({\mathrm{H}}_{i})$ makes multicenter bond and acts as a shallow donor. In addition, H as adatom (H-ad) also provides shallow donor levels and is the cause of unintentional $n$-type doping. Among the extrinsic defects, halogens and transition metals are found to be promising dopants. While halogens at the S site act as shallow donors, Nb at the W site provides a reasonable shallow acceptor level with low formation energy.