Nanodots of transition metal dichalcogenides embedded in MoS2 and MoSe2: first-principles calculations

Abstract

The energetic stability and the electronic properties of nanodots (NDs) composed of transition metal dichalcogenides, XS₂ and XSe₂ (with X = Mo, W and Nb) embedded in single layer MoS₂ and MoSe₂ hosts, were investigated based on first-principles calculations. We find that through a suitable combination of the ND and host materials it is possible to control the electron–hole localization. For instance, in NDs of WS₂ in the MoS₂ host we find the highest occupied (hole) states localized in the ND region, while the lowest unoccupied (electron) states spread out in the MoS₂ host. On the other hand, by changing the ND and host materials, the electron states become localized in the MoS₂ ND in the WS₂ host. Further electronic structure calculations show that the NDs of NbS₂ and NbSe₂ give rise to a set of spin degenerate empty states within the energy gap of the MoS₂ and MoSe₂ hosts. The spin degeneracy can be removed by negatively charging the ND system. Such n-type doping was examined by considering a van der Waals (vdW) heterostructure composed of a graphene layer lying on the NbS₂ and NbSe₂ NDs. Indeed we found a net magnetic moment localized in the ND region.