Using a Green’s function method, surface phonon spectra were calculated for the (111) surfaces of these diamond-structured crystals on the basis of a phenomenological force-constant model. Allowing for changes in the surface force constants, the possibility of surface phonon softening was investigated. Upon relating these soft modes to surface reconstructions, evidence was found for Si (7 x 7), Ge (8 x 8) and α-Sn (3 x 3) reconstructions, while diamond did not exhibit any soft-mode behaviour. The occurrence of different surface structures on these geometrically identical crystals could therefore be explained as already being determined to a great extent by bulk properties. Finally, models of the reconstructed surfaces were derived, and a model for the Si (7 x 7) surface was considered with respect to experimental transmission electron diffraction patterns.

Surface Modes and Reconstruction of Diamond Structure Crystals. W.Goldammer, W.Ludwig, W.Zierau: Surface Science, 1986, 173[2-3], 673-85