▎ 摘　　要

The stability and the electronic structure of layered heterostructures MX2 (M = Mo or W and X = S or Se) and graphene (GA) are systematically investigated using firest 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 MX2 on undoped GA substrate, whether pristine or defected, follows a Volmer-Weber growth-mode resulting in thick MX2 films. On the other hand, nitrogen doping of pristine GA (N-GA) and also of GA with Stone-Wales (SW) defects increases the MX2/GA heterostructure adhesion energy favoring the growth of ultrathin MX2 layers. This growth-mode change in MoS2 due to nitrogen doping is in agreement with recent experiments. Furthermore, our study demonstrates that the yield of ultrathin MX2 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.