Electronic Detection of Oxygen Adsorption and Size-Specific Doping of Few-Atom Gold Clusters on Graphene*

Graphene has potential application as sensor due to its sensitivity to adsorbed particles. Few-atom clusters are promising candidates as adparticles on graphene. In this joint experimental and computational work, we investigate size-selected gold clusters with 3 and 6 atoms adsorbed on graphene field-effect transistors and their interaction with molecular oxygen. We find that the doping level of graphene significantly depends on the cluster size, in the absence or presence of oxygen molecules. Furthermore, the doping of 3-atom gold cluster decorated graphene changes sign from n- to p-doping upon oxygen adsorption, directly evidencing electron transfer to the oxygen molecules and hence their activation. As such, graphene promises to be a valuable platform to investigate and exploit size-dependent cluster properties. The presentation covers mainly the theoretical aspects of the work, namely density functional theory (DFT) based simulations of adsorption site, adsorption energy, atomic configuration, and electronic structure.