Electronic structure of Si(113)2 × 2-Cs surface studied by ARUPS

Abstract

The electronic structure of aSi(113)2 × 2-Cs surface has been investigated by low energy electron diffraction (LEED) and angle-resolved ultraviolet photoelectron spectroscopy (ARUPS). The surface-band dispersions were measured along the symmetry axes, Γ-U[33¯2] and Γ-W[1¯10], in the surface Brillouin zone. Three surface states were observed at the binding energy of 0.7 (A 1), 0.95 (A 2), and 1.65 eV (A 3) below the Fermi level at Γ with overall dispersions of about 0.15, 0.5, and 0.2 eV, respectively. The A 2 and A 3 states revealed a2 × 2 periodicity along the [33¯2] direction. Considering the alkali-metal adsorptions on low-index Si surfaces and measured Cs 3d/Si 2p XPS peak intensity ratios, the Cs-saturation coverage of the2 × 2-Cs surface was assigned to about6/8 monolayer. Based on the Cs-saturated adatom + tetramer model, the A 1 and A 2 states are identified as Cs-induced adatom and tetramer states, respectively. The A 3 state has a surface resonance-like character.