Functionalization of CVD Graphene Using Physisorbed Self-Assembled Monolayers

Tailoring the electronic properties of graphene in a controlled way is imperative for its use in future electronic applications. Among several approaches for tailoring the charge carrier concentration, i.e., doping graphene, functionalization of the graphene surface using physisorbed organic adsorbates is advantageous as it does not hamper the charge carrier mobility of graphene. Here we introduce doping of graphene grown by chemical vapor deposition (CVD) using organic electron donor and acceptor compounds that self-assemble into 2D networks on the graphene surface. These well ordered networks offer precise control over the density of molecules on the surface and thus over the graphene surface properties including doping levels and surface chemistry [1]. The organization of the compounds on the surface of graphite and graphene was characterized using scanning probe microscopy techniques. The doping effect of the self-assembled monolayers was probed via Raman spectroscopy and the electrical characterization of graphene field effect transistors. AFM measurement showed that the compounds can be deposited uniformly on graphite with control over the film thickness down to monolayer coverage. Using high resolution scanning tunneling microscopy (STM) it was shown that the molecules organize in a similar close-packed structures on CVD graphene as seen on graphite. In conclusion, this study is the first step towards tunable and controlled modification of the electronic properties of graphene.