Si 2p core level spectroscopy in Si(001)2x1: the charge-transfer effect

Analysis of high-resolution Si 2p photoemission spectra recorded from a clean Si(001)2x1 surface clearly reveals seven components. Four of them are surface-related emission with core-level binding-energy shifts (SCLS) of -500, 278, -200, and 138 meV, which are associated with up and down atoms in the dimers, atoms in symmetric dimers, and subsurface atoms, respectively. The other two loss components appear at 1.3 and 1.75 eV, associated with the bulk and surface, respectively. The latter loss structure corresponds to the transitions of dimer-related electronic states. The components assigned to the surface dimer show significant line shifts and broadenings upon C-60 adsorption, whereas the component to the subsurface layer does not. The present result from a modified model function supports the predominance of the initial charge-transfer effect to the SCLS in Si, as in the case of Si(111)7 x 7. (C) 1998 Elsevier Science B.V. All rights reserved.