Pb/Si(1 0 0)2×1 surface studied by high resolution core-level photoemission spectroscopy

A Pb/Si(100)2×1 surface has been studied at T = 120 K by high resolution core-level spectroscopy using a third generation synchrotron light source. A strong component (S), could be identified at a binding energy (BE) of -0.20±0.01 eV with respect to the bulk peak. This is indicative of some reorganization of the topmost silicon atoms after Pb adsorption with the formation of Si-Pb bonds and Pb-Pb symmetric dimers. However, this shift is in the opposite site respect to the bulk peak, as compared with Sb/Si(100)2×1, thus suggesting the interplay of final states screening effects and charge transfer in the core-level position. Another component (smaller than S) is present at +0.15 eV BE, and might be due to contribution from subsurface silicon atoms, as on the clean surface, and/or to surface or interface defects. On the Si2p core-level taken in bulk sensitive mode, we found a very narrow bulk component with a total full width half maximum (FWHM) of 160 meV at T = 120 K indicative of an unreacted Si-Pb interface on top of an ideal Si bulk termination. The Pb5d core-level spectrum is well represented by one doublet, thus suggesting that each Pb atom is adsorbed in a unique environment, i.e., there is no multisite adsorption. © 2003 Elsevier B.V. All rights reserved.