Abstract
Chemically hydrogenated Si(111) surfaces have been investigated in ultrahigh vacuum by photoemission yield spectroscopy (PYS) and characterized by low-energy electron diffraction (LEED) and Auger electron spectroscopy (AES). From Kane's theory [1] the valence state contribution to photoemission yield at threshold in Si follows a power law Y(h nu)proportional to(h nu-E-T)(m) in which m greater than 1 indicates electron scattering; E-tau being the threshold energy. By combining AES and LEED indications with the values of E-T and m as determined by a fit with measured yield spectra, it is shown that traces of oxygen chemisorbed in the Si top layer can be distinguished for similar amounts adsorbed along the Si surface as OH radicals. Other effects of trace defects are also shown. (C) 1998 Elsevier Science B.V. All rights reserved.