Panoply of doping-induced reconstructions and electronic phases in Ni-doped 1T-MoS₂

Transition metal doping of monolayer MoS₂ can tune its structure and optoelectronic properties. We use density functional theory to investigate the effect of Ni-doping in metastable metallic 1T-MoS₂, considering adatom and substitutional sites, and find an array of distorted phases induced by Ni-doping [arXiv:2107.07541]. Doping is thermodynamically favored compared to the undistorted 1T. Depending on concentration and site, Ni-doping induces reconstructions to 2×2, √3×√3 (in two distinct phases), 3×3, and 4×4. The doped phases become semiconducting in most cases, and a few are also magnetic. These phases are metastable after removal of the dopant, offering a potential route to the experimental synthesis of pristine distorted phases.  These distorted pristine phases show spontaneous polarization, so they are potential ferroelectric materials. We find that the pristine phases have distinct semiconducting electronic structures, including several higher gaps in the conduction bands, which could be interesting for transparent conductors and intermediate band solar cells. Our calculations show that Ni-doping of 1T offers a systematic route to different distorted phases of 1T-MoS₂, both doped and pristine, with a variety of electronic properties.