Ab initio study of the Surface Passivation influence on electronic and optical Properties of (001) SbNSr3 anti-perovskite Surface

In this research, the electronic and optical properties of the (001) surface of SbNSr3 with SbSr and NSr2 terminations and surface passivation impact on electronic properties were investigated. The calculations were done within density functional theory and using pseudo-potential method. HSE hybrid functional was used for exchange correlation potential. The surface calculations were performed taking into account tetragonal supercell, periodic boundary conditions, sufficient vacuum and minimum force on atoms. Results of the electronic calculations show that despite the semiconducting nature of the SbNSr3 bulk, the electron states were observed near the Fermi level. The active surface bonding was saturated through adsorbing hydrogen atoms on the surface. Due to this, the electron states were removed and opened the band gap in both terminations. The calculated band gap of the SbSr and NSr2 terminations were calculated 0.808 and 1.029 eV, respectively. The optical properties of the SbNSr3 surface were investigated without and with the surface passivation. The results showed that in both terminations, the surface passivation which causes the elimination of surface electron states, leads to an increase in the optical gap. The calculated optical gap in both bare and passivated surfaces for the polarized incident light in the direction perpendicular to the surface was obtained greater than in the direction parallel to the surface. The optical gap of the SbSr termination was calculated to be less than that of the NSr2 termination in agreement with the results of the electronic calculations. It was also observed that the static dielectric constant at both terminations decreases with surface passivation and the static dielectric constant in the z-direction is less than in the x- direction.