The effective utilization of graphene in optoelectronic devices requires blending with other semiconductor materials, such as lead chalcogenide nanocrystals, and an understanding of the organic–inorganic interface at the atomic level. In this paper, we present the first report of the successful self-assembly of close-packed monolayer arrays of PbTe nanocrystals on monolayer graphene. By using ultraclean chemical vapor deposition grown graphene and aberration corrected transmission electron microscopy the unambiguous delineation of a ∼2 nm soft ligand nanocrystal shell is achieved, which is compared to subsequent studies after ligand exchange is performed on the same nanocrystal-graphene hybrid. Ligand exchange was shown to remove the soft ligand shell surrounding the nanocrystals and to disassemble the close-packed monolayers into amorphous nanocrystal aggregate film on the graphene substrate. Limited oriented attachment between nanocrystals in the anisotropic film was observed, and this was not significantly affected by extended vacuum annealing.

PbTe nanocrystals were deposited onto the surface of graphene and used as a reservoir of Pb and Te atoms. Electron beam irradiation at 80 kV caused Pb and Te atoms to mobilize and disperse across the surface of graphene. We studied the dynamics of these atoms in real time using aberration-corrected transmission electron microscopy. The Pb and Te atoms were found to attach to the surface layer of amorphous carbon that resides upon the graphene, as well as its edge. Pb and Te atoms were not found residing on pristine graphene, but were found to bond to the free edge states along graphene hole edges. Small PbTe nanoclusters tended to only form on the surface of the amorphous carbon regions and not on pristine graphene.

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