Structural and Electronic Properties of Functionalized Graphene

In the present paper, we study the effects of functionalization of graphene with simple organic molecules OH, and $NH_2$, focusing on the stability and band gaps of the structures. We have performed DFT calculations for graphene supercells with various numbers of the attached molecules. We have determined adsorption energies of the functionalized graphene mono- and bilayers, the changes in the geometry, and the band structure. We observe the characteristic effects such as rehybridization of the bonds induced by fragments attached to graphene and opening of the graphene band gap by functionalization. We have also studied the dependence of the adsorption energies of the functionalized graphene on the density of the adsorbed molecules. Our calculations reveal that the -OH and $-NH_2$ groups exhibit the strong cohesion to graphene layers. Further, we determine the critical density of the OH fragments which lead to the opening of the band gap. We also show how to engineer the magnitude of the band gap by functionalizing graphene with $NH_2$ groups of various concentrations.