Geometry-dependent Si(2p) surface core-level excitations for Si(111) and Si(100) surfaces

Structure-dependent Si(2p) surface core-level shifts and 2p photothreshold spectra which yield new surface geometry information are reported. For Si(100)-(2×1), 0.5 monolayer of surface atoms are found shifted to smaller binding energy (-0.5 eV) relative to the bulk; this rules out symmetric pairing models. Si(111)-(7×7) and Si(111)-(2×1) show different surface 2p core-level spectra (e.g., 16 layer shifted -0.7 eV versus layer shifted - 0.4 eV), suggesting different geometries. Si(111)-(1×1)H exhibits first-layer (+ 0.26 eV) and second-layer (+ 0.15 eV) shifts. © 1980 The American Physical Society.