Estudo de monocamadas e bicamadas de grafeno dopadas com metais alcalinos e halogênios via DFT

Abstract

In this work we present a study of the doping of graphene (mono and bi-layer) with atoms of the alkali metal and halogen families. The charge transfer and binding energy between the dopant and the graphene were calculated under the light of the Density Functional Theory using the SIESTA code. The effect of the interaction between the dopant and the graphene to its electronic structure was also analized, focusing on a possible metal-insulator transition. Both the monolayer and the bilayer graphene sheets were doped with lithium (Li), sodium (Na) and potassium (K), among the alkali metals; and with chlorine (Cl) and iodine (I), among the halogens. Furthermore, in the case of the bilayer graphene, we also studied the effect of doping each sheet with a different atom (Li and Cl). For the monolayer graphene, none of the dopants were able to open an energy gap in the graphene electronic structure. This suggests that the charge transfer does not change the hybridization of the carbon atoms in the graphene. On the other hand, for the bilayer graphene, the interaction with either of the doping atoms was able to give rise to an energy gap. However, the charge transfer changed the Fermi energy in such way that there was always a considerable amount of free charges. The exception is in the case of the bilayer graphene doped with both lithium and chlorine, for which the Fermi level stayed in the middle of the energy band gap, characterizing a semiconducting nature to the system.