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

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 x 3 x 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 F-2 and I-2 have the same stable position on and parallel to the h-BN, in contrast to Cl-2 and Br-2 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. (C) 2019 Published by Elsevier B.V.