Van der Waals Epitaxial Growth of Transition Metal Dichalcogenides on Pristine and N-Doped Graphene

The stability and the electronic structure of layered heterostructures MX 2 (M = Mo or W and X = S or Se) and graphene (GA) are systematically investigated using first-principles methods. The calculations cover pristine and defected GA systems with up to 12% nitrogen substitutional defects. It is found that the van der Waals (vdW) epitaxy of MX 2 on undoped GA substrate, whether pristine or defected, follows a Volmer–Weber growth-mode resulting in thick MX 2 films. On the other hand, nitrogen doping of pristine GA (N-GA) and also of GA with Stone–Wales (SW) defects increases the MX 2 /GA heterostructure adhesion energy favoring the growth of ultrathin MX 2 layers. This growth-mode change in MoS 2 due to nitrogen doping is in agreement with recent experiments. Furthermore, our study demonstrates that the yield of ultrathin MX 2 films can be increased if the N-GA samples have a larger concentration of SW defects or nitrogen. The underpinnings of the extra stability of these N-GA substrates are due to charge-transfer effects that decrease the Pauli repulsion between the two layered systems.