SCATTERING OF ELECTRONS IN THE SURFACE REGION OF SOLIDS STUDIED BY APPEARANCE-POTENTIAL SPECTROSCOPY

Ultrathin chromium layers of increasing thickness were deposited on ti tanium substrates under UHV conditions. AFM was used to check the surf ace morphology and to optimize the evaporation parameters. In-situ AES and APS measurements were performed on these samples. The APS overlay er and substrate signal intensities, as a function of the overlayer th ickness, have been measured. Instead of the common exponential model o f the overlayer signal rise and the substrate signal attenuation, resp ectively, the discrete model according to Eckertova' was used to fit t he experimental results. Its parameters represent the probabilities of the basic types of the electron interactions at one atomic layer. App roximate values of these quantities have been calculated.