A study of surface band bendings and charge densities of SiC(001) 2x1 and c(2x2) by high-resolution electron-energy-loss spectroscopy

Collective surface excitations (Fuchs-Kliewer optical phonons and plasmons) of Si-terminated (2 x 1)- and C-terminated c(2 x 2)-surfaces are studied by high-resolution electron-energy-loss spectroscopy (HREELS) for high and low n-doped SiC(001). Because of the large effective electron mass in SiC the surface plasmon is not distinctly resolved even at a doping level of 2.5 x 10(18) cm(-3) However, a strong asymmetric broadening of the quasielastic peak is observed. By virtue of the model based on the dipole scattering theory, the main features of this broadening for various experimental conditions like primary beam energy and surface reconstruction can be elucidated. From the fits of the measured energy-loss spectra important parameters like bulk free-electron concentration and its variation with depth beneath the surface, band bending, electron mobility and plasmon damping Factor are determined. (C) 1998 Elsevier Science B.V. All rights reserved.