Investigation on effect of boron and nitrogen substitution on electronic structure of graphene

Abstract

Necessity of opening of energy gap in the band structure of, otherwise a zero gap semiconductor, graphene, is a must for its use in fabrication of high speed electronic devices. One such technique, for opening of energy gap in graphene, is by way of doping the pristine graphene with boron or nitrogen. Besides many important applications, to which B- and N-doped graphene has been put, the one very important for solving the global energy crisis is by way of its capacity for hydrogen storage. In this paper electronic structure of B- and N-doped graphene has been studied by using Density Functional Theory, as implemented in WIEN2K code. PBE-GGA (Perdew–Burke–Ernzerhof 96) pseudo-potential is used for solving the Schrodinger equation in self-consistent manner and to account for the exchange and correlation effects through the use of Generalized Gradient Approximation. The band structure calculations reveal that whereas a band gap opens at the symmetry point K both for B- and N-doped graphene, the center of the gap (i.e., the Dirac point in pristine graphene) is shifted above the Fermi level by about 2.20eV for B-doped graphene, and shifted down the Fermi level by about the same amount for N-doped graphene, when the doping level was kept 25% in each case. The energy gap opened was found to be about 0.30eV for B-doped graphene and 0.45eV for N-doped graphene. The linear dispersion characteristics obtained at Dirac point for pristine graphene, almost vanish for B-/N-doped graphene, due to symmetry breaking and opening of energy gap. The band structure and Density of States of B-/N-doped graphene are found also to depend on the choice of cell parameters.