An X-ray photoelectron spectroscopy study of the bonding of unsaturated organic molecules to the Si(001) surface

The core-level binding energies of simple unsaturated organic molecules bonded to the Si(001) surface have been investigated using X-ray photoelectron spectroscopy (XPS). Using the Si 2p levels as an internal standard, the shifts in carbon and nitrogen levels were analyzed for a series of small unsaturated molecules, including cyclopentene, ethylene, acetylene, 3-pyrroline and pyrrolidine, adsorbed on the Si(001) surface. Alkene-like carbon atoms are found to have binding energies 0.6-0.9 eV higher than alkane-like molecules. Carbon atoms bonded directly to the silicon surface show binding energies 0.7-0.8 eV lower than those that are not bonded directly to silicon. The N Is binding energy is decreased by 0.9 eV by bonding to silicon. The use of XPS for identification of bonding configurations of unsaturated organic molecules on the silicon (001) surface is discussed. (C) 1998 Published by Elsevier Science B.V. All rights reserved.