DFT study on electronic and optical properties of halogen-adsorbed hexagonal boron nitride

Abstract

In this paper, electronic and optical properties of two-dimensional (2D) hexagonal structure of boron nitride (h-BN), such as its band structures, energy gap, projected density of states (PDOS), dielectric function and adsorption coefficient under adsorption of halogen molecules are studied. A theoretical investigation is presented to find out the most stable atomic site for each halogen molecule to adsorb on a single layer of h-BN. The calculations are performed on a 3 × 3 × 1 supercell of h-BN within the framework of density functional theory (DFT) to have the best consistency with the existing experimental data. The results show that the h-BN is an insulator with a band gap of 4.91 eV. Investigating the most stable site and energy gap’s fluctuation in the h-BN under halogen molecules adsorption shows that F2 and I2 have the same stable position on and parallel to the h-BN, in contrast to Cl2 and Br2 with another same stable site perpendicular to the h-BN layer. It is found out that in all cases halogens decrease the electronic band gap of the h-BN. Real and imaginary parts of dielectric functions for pristine and halogen adsorbed single-layer h-BN are investigated. Optical absorption and reflection curves reveal the optical blindness of the system to the visible range of light, while it fulfills the requirements of ultraviolet (UV) light detection.