An ion-bombardment-cleaned Ge(111) surface was observed to undergo (√3 x √3)R30° reconstruction prior to the (2 x 8) reconstruction. This (√3 x √3) surface structure was also observed upon adsorption of Li and Ag. By comparing the measured low-energy electron-diffraction I-V curves of the clean surface (√3 x √3) reconstructed structure with those of (√3 x √3) structures of the Li- and Ag-adsorbed surfaces, it was concluded that all (√3 x √3) structures result from surface reconstruction. In addition, a (1 x 3) structure on the Ge(111) surface was also observed as a result of the adsorption of Li, Na, and K. The equivalence of the I-V curves for the three (1 x 3) structures indicated that germanium surface reconstruction was responsible for the (1 x 3) structure. The coverage dependence of the alkali-metal-induced reconstructions was identified.

Reconstruction of the Clean and Metal-Adsorbed Ge(111) Surface. W.C.Fan, A.Ignatiev: Physical Review B, 1989, 40, 5479-83