Interfacing the inert basal plane of graphene with other materials has limited the development of graphene-based devices. Here, we present the growth of ZnO nanoparticles on epitaxial graphene (EG) on SiC(0001) using a combination of scanning probe microscopy, Raman spectroscopy, and density functional theory (DFT). The nanoparticles are obtained by sequential exposure of EG to atomic oxygen (AO) and diethyl-zinc (DEZ) precursors under ultrahigh vacuum conditions. Atomic force microscopy shows that this process creates regularly sized nanoparticles on the surface of EG, while X-ray photoelectron spectroscopy confirms the chemical identity of these nanoparticles as ZnO. DFT calculations provide the following mechanism for nanoparticle growth. First, the exposure to AO leads to epoxide functionalities on EG. Then, exposure to DEZ leads to two subsequent oxygen atom abstractions from the surface to form diethoxy-zinc (DEoZ) that either docks to remaining epoxy sites or reacts with other precursors. In further AO and DEZ cycles, the epoxy functionalization of EG and oxygen atom abstraction by DEZ continues, in addition to the growth of ZnO clusters. The structural integrity of the underlying EG upon ZnO growth is confirmed by Raman spectroscopy. The nanoparticle growth can be controlled using AO exposure (it determines the amount of available oxygen on the surface of EG) or temperature (an optimum growth temperature is expected: higher temperature is required for faster oxygen abstraction, whereas lower temperature suppresses precursor/intermediate desorption from surface). The method we present here can likely be generalized to a wide variety of related surface reactions on graphene.

Metal oxide nanoparticle growth on graphene via chemical activation with atomic oxygen

247th National Meeting (2014)

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