Vibrations at 3C-SiC(001)-(3 x 2) surfaces

Si-terminated 3C-SiC(001) surfaces with (3 x 2) and (2 x 1.) reconstructions were investigated by high-resolution electron energy-loss spectroscopy (HREELS), low-energy electron diffraction (LEED) and Anger electron spectroscopy. The surfaces were prepared by subsequent annealing steps after cleaning by heating in a Si flux. At (3 x 2)-reconstructed surfaces, the HREELS intensity increases while the widths of the loss lines decrease with proceeding preparation. Eventually, weak loss structures at 380 and 700 cm(-1) are detected besides the strong Fuchs-Kliewer phonon loss peaks. They are attributed to surface-localized vibrations, i.e., to stretching modes of on-top Si dimers and of C-Si-C groups, respectively. The weak features vanish after exposure to atomic deuterium, but reappear after subsequent annealing. At (2 x 1) reconstructed surfaces the HREELS lines are broadened and no surface-localized modes were resolved.