PbTe Nanocrystal Arrays on Graphene and the Structural Influence of Capping Ligands

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