Wsm. Werner et al., Angular dependence of the surface excitation probability for medium energyelectrons backscattered from Al and Si surfaces, J VAC SCI A, 19(5), 2001, pp. 2388-2393
Reflection electron energy loss, spectra have been measured for medium ener
gy electrons backscattered from Al and Si surfaces. Angular distributions w
ere obtained for emission angles between 15 degrees and 90 degrees with res
pect to the surface normal as well as for incidence angles in the same rang
e. The surface excitation parameter (SEP), i.e., the average number of surf
ace excitations an electron experiences when it crosses a surface once, was
extracted from each spectrum by fitting the raw data to theory and determi
ning the ratio of the surface loss peak to the elastic peak intensity. No d
ifference in the SEP for incoming and outgoing electrons could be detected
in the data. The SEP was found to depend linearly on the, time an electron
spends in the vicinity of the surface. Both the energy and angular dependen
ce of the SEP can be accurately described by free-electron theory when the
electron momentum is rescaled by a material-dependent parameter. The value
of the scaling parameter is given for Al and Si so that the SEP in these ma
terials can accurately be predicted for medium energies and arbitrary exper
imental configurations. (C) 2001 American Vacuum Society.