The electronic and diffusion properties of metal adatoms on graphene sheets: a first-principles study

We use first-principles calculations to investigate the geometric, electronic and magnetic properties of metal adatoms on two typical graphene substrates (monolayer and bilayer). Firstly, we study the adsorption behaviors and the doping effects of metal atoms on pristine and defective bilayer graphene sheets (PBG and DBG). It is found that the metal doping in DBG sheets is more stable than that in PBG sheets, since there are stronger covalent bonds between metal atoms and the dangling bonds of the carbon atoms. Compared to the unsupported graphene sheets, the Pt(111) supported graphene substrates have some effect on the stability of metal adatoms. Besides, the diffusion pathways of metal adatoms move from the upper pristine layer to the sublayer with large energy barriers, which is more difficult than that on the upper layer of DBG and the intercalated reaction from the upper layer to the sublayer, so the metal adatoms tend to penetrate into the graphene overlayer through the defective site. Moreover, the different metal adatoms can effectively regulate the electronic and magnetic properties of graphene sheets. This work provides valuable information on understanding the formation mechanisms of metal doping in graphene sheets, which would be vital for designing new functional metal-graphene composites.