Electronic and optical properties of Pmmn borophene modified by doping : a DFT approach

Borophene nanosheet has been doped with lithium, beryllium, carbon and hydrogen atom. Modification of electronic properties through the splitting and shifting of Dirac point has been explored within the framework of ab - initio density functional theory (DFT). Indirect band gap opening is noticed when the system is doped with one hydrogen atom. But when the doping concentration is made double, the system becomes metallic. For lithium and beryllium doping, the split Dirac point has been observed to be situated at the conduction band. However, for single site carbon atom doping, it is seen to be situated at the valence band while, for double concentration, the system becomes semiconducting with an indirect band gap of 528 MeV. Optical calculations show that for parallel and perpendicular polarization, the excitations have mainly occurred within the low and high energy regions respectively. Some salient features of optical results can be understood from the electronic band structures. (author)