SURFACE CORE-LEVEL SHIFT AND PHONON BROADENING IN PBS(100)

In situ cleaved PbS(100) surfaces were studied by means of X-ray photo electron spectroscopy (XPS) using synchrotron radiation. A significant narrowing of the S 2p, Pb 5d and Pb 4f lines was found at low tempera tures, indicating strong dependence of phonon broadening on temperatur e. The narrowing was found to be strongest for the S 2p surface peak. This phenomenon made it possible to observe, for the first time, a sur face core-level shift (SCLS) in the S 2p lines of PbS. No SCLS was obs erved for the Pb 5d and Pb 4f lines, which is in agreement with Paoluc ci and Prince, Phys. Rev. B 41 (1990) 3851. Also, the inelastic mean f ree paths (IMFP's) for the photoelectrons were determined. (C) 1998 El sevier Science B.V. All rights reserved.