Ab-initio investigations on physisorption of alkaline earth metal atoms on monolayer hexagonal boron nitride (h-BN)

First-principles density functional theory (DFT) calculations are performed on the structural, electronic, magnetic and optical properties of alkaline earth metal (AEM) atoms-adsorbed hexagonal boron nitride (h-BN) structures. Different AEM atoms were adsorbed on the hollow (H) and bridge sites of monolayer h-BN and their effects on aforementioned properties were then investigated. Calculated adsorption energies indicate that, the physisorption of AEM atoms on h-BN layer is thermodynamically favorable. It is also observed that, the charge transfer occurs from AEM atoms to the h-BN layer. When AEM atoms were adsorbed at H-site of h-BN layer, only Mg and Sr atom adsorption introduced significant magnetic moments of 2.0 μB and 1.0 μB, respectively. During AEM atoms adsorption at bridge site, Ca, Mg and Sr atoms adsorption induced 1.92 μB, 1.98 μB and 0.712 μB magnetic moments in h-BN layer, respectively. Through electronic structure calculations, it is observed that, AEM atom adsorption on h-BN significantly modifies its band structure, by converting wide bandgap h-BN semiconductor to the half metal and/or semimetal. Through density of states (DOS) plots, it is revealed that, s and p orbitals of AEM atoms are mainly responsible for arising of magnetic moments in monolayer h-BN. Finally, the optical parameters specifically, absorption coefficient and reflectivity plots for AEM atoms adsorbed h-BN structures were obtained using DFT within random phase approximation (RPA). Pure h-BN layer presents zero absorption coefficient and low static reflectivity in low lying energy range. However, AEM atom adsorption on h-BN layer produces an increment in absorption coefficient quantity in 0-4 eV energy interval. Similarly, the higher reflectivity parameter is obtained in lower energy range. These obtained results predict that, the AEM atom adsorption on monolayer h-BN carries potential applications for nanoelectronics, spintronic and optoelectronic device applications.