Scanning tunnelling microscopy and low-energy electron diffraction were used to investigate Ge(111) vicinal surfaces misoriented by 1° and 2° towards the (112) and (112) high-symmetry directions, respectively. Surfaces of moderately Ga-doped (dopant concentration ≈1019/cm3) Ge reconstructed to c(2 x 8). No straight step edges, but meandering kinks between terraces, were observed by scanning tunnelling microscopy. For highly Ga-doped (≈2 x 1020/cm3) Ge crystals, rich in dislocations and Ga inclusions, the vicinal surfaces exhibited - at room temperature - a previously reported low-energy electron diffraction pattern for a phase of the well-oriented clean Ge(111) surface appearing at approximately 300C. Scanning tunnelling microscopic images at room temperature clearly exhibited the incommensurate honeycomb-domain reconstruction, I(2 x 2), proposed by Phaneuf et al. (1985) in order to explain the low-energy electron diffraction pattern. A high dislocation density and misorientation appeared to be essential in order to observe this reconstruction. This appeared to be the first real-space observation of such a structure.

The Structure of Vicinal (111) Surfaces of Perfect and Dislocation-Rich Ge Crystals Doped with Ga. P.Molinas-Mata, J.Zegenhagen, A.Hopner, H.Bender, E.Schonherr, H.Labitzke: Journal of Physics - Condensed Matter, 1993, 5[27], 4687-94