Quantum-well states for uniform Ag layers on the Ga-induced Si(111)–([formula omitted])R30° surface

Abstract

The atomic and electronic structures are calculated for atomically uniform Ag layers on the Ga–induced Si(111)–(3×3)R30° surface by using the Density Functional Theory. It is found that when the amount of Ag atoms increases on the 1/3 monolayer Ga–induced Si(111)–(3×3)R30° surface, the equilibrium T4 adsorption site of Ga atom changes to the T1 site. We have determined a single covalent bond between Ga and Si atoms but there is some charge accumulation on the Ga–Ag layer, turning the surface to metallic nature. For 10 Ag monolayers, we have determined evolution of several quantum-well states within the energy range of 1 eV below the Fermi level. The energy separation between the quantum well states increases as their numbers develop below the Fermi level. The Ag film quantum-well states show in-plane parabolic dispersion, with splittings arising due to Umklapp features related to the Si(111)–(1×1) surface Brillouin zone. We have also identified Shockley type surface states, which show small Rashba-type spin-orbit splitting.