Impact of a van der Waals interface on intrinsic and extrinsic defects in an MoSe₂ monolayer

In this work, we study growth and migration of atomic defects in MoSe₂ on graphene using multiple advanced transmission electron microscopy techniques to explore defect behavior in vdW heterostructures. A MoSe₂/graphene vdW heterostructure is prepared by a direct growth of both monolayers, thereby attaining an ideal vdW interface between the monolayers. We investigate the intrinsic defects (inversion domains and grain boundaries) in synthesized MoSe₂, their evolution amid growth processing steps, and their influence on the formation and movement of extrinsic defects. Electron diffraction identifies a preferential interlayer orientation of 2° between MoSe₂ and graphene, which is caused by the presence of intrinsic IBD defects. Extrinsic defects (point and line defects) are generated by in situ electron irradiation in the MoSe₂ layer. Our results shed light on how to independently modify the MoSe₂ atomic structure in vdW heterostructures for potential utilization in device processing.