Surface state-derived electronic transitions of SiC(001)

We report on collective surface excitations at Si-terminated (2 x 1) and C- terminated c(2 x 2) surfaces of SiC(001) by using high-resolution electron energy loss spectroscopy (HREELS). The measured energy loss spectra are fit ted by two different models based on dipole scattering theory. While the fi rst model takes account of the Fuchs-Kliewer surface optical phonons and su rface plasmons only, the second one contains, additionally, a contribution from intraband plasmons due to the presence of a partially occupied surface states band. For both surfaces much better fits are obtained by the second model, i.e. if we assume the surfaces to be metallic. For the (2 x 1) surf ace this finding is in agreement with recent STM results suggesting the met allic character of this surface at high temperatures. (C) 1999 Elsevier Sci ence B.V. All rights reserved.