Atypical behavior of intrinsic defects and promising dopants in two-dimensional WS2

The 2D-WS2 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 2D-WS2. All the intrinsic defects and their complexes are found to be deep and self-compensating. S vacancy (V-s), which has been previously attributed as the source of n-type conductivity, turns out to be an electron trap center. We found that V-s gives rise to a suboptical gap, which can be the source of single-photon emitters. Interestingly, hydrogen interstitial (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.