Electronic structure of Si(100)2×1-Cl studied with angle-resolved photoemission

The chlorine-chemisorbed Si(100)2×1-Cl surface has been studied with polarization-dependent angle-resolved photoemission, employing single-domain surfaces obtained from vicinal Si(100) samples. Contributions from seven Cl-induced surface-state bands are identified in the photoemission spectra in the energy range 5.1–9.4 eV below the Fermi level. One band, at about -8.2 eV initial energy, is attributed to Si-Cl bonding orbitals of mainly ${\mathit{p}}_{\mathit{z}}$ character, while four of the higher-energy bands are associated with Cl nonbonding orbitals of mainly ${\mathit{p}}_{\mathit{x}}$,${\mathit{p}}_{\mathit{y}}$ character. A very weak structure at about -9.4 eV initial energy is attributed to Si(s)-Cl(${\mathit{p}}_{\mathit{z}}$) bonding states. The polarization dependence of the five upper bands in the Γ¯-J¯ and Γ¯-J¯’ directions of the surface Brillouin zone indicates mirror-plane symmetries consistent with a symmetric dimer model.