Grafenin işlevleştirlmesinin ilk prensip teknikleriyle incelenmesi

The graphene sheet is a single-atom thick novel material and attracts greatinterest due to its unique features. However, it is a metallic material with nobandgap, which makes it di cult to integrate in electronic applications. Adatomadsorption is one of the promising ways to make this structure functional. Tothis end, electronic and structural properties of graphene have been investigatedby using density functional theory formalism in order to understand atomic levelinteraction between halogen adatoms and graphene layer. The most commonadatom, hydrogen, has also been studied. In this study, plane-wave, pseudo-potential density functional theory calculations were carried out using generalizedgradient approximations for the exchange correlation potential with the QuantumEspresso package. In order to obtain fully relaxed structures, geometry optimiza-tion has been performed in all of the calculations. The adatom-graphene systemis modelled with a 4 4 graphene supercell. Adsorption energies of halogenadatoms and dimers adsorbed on highly symmetric positions on graphene layerare calculated. Dierent con gurations of adatoms have been tested. Speci cproperties such as band structure and density of states of these system have beeninvestigated. The results show that a fully covered graphene layer is stable andoptimized structures exhibit a band gap of a few eV. The most stable structureamong halogen adatoms is the uorine adsorbed on graphene. It has the highestelectronegativity, which is the reason for high electron transfer from the graphenelayer. This is the reason of the formation of covalent bonds. Furthermore, themost stable con guration is found to be chair con guration with the halogenatoms alternating in both sides of the layer.Keywords: graphene, adsorption on graphene, graphane, halogen atoms, DFT,plane-wave pseudo-potential calculations