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

Analysis of high-resolution Si 2p photoemission spectra recorded from a cle an Si(001)2x1 surface clearly reveals seven components. Four of them are su rface-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 th e dimers, atoms in symmetric dimers, and subsurface atoms, respectively. Th e 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 th e transitions of dimer-related electronic states. The components assigned t o the surface dimer show significant line shifts and broadenings upon C-60 adsorption, whereas the component to the subsurface layer does not. The pre sent 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.