STEP STRUCTURE AND SURFACE RECONSTRUCTION ON VICINAL GE(111) SURFACES

The thermal evolution of the reconstruction and step structure of Ge(111) surfaces misoriented by 6-degrees and 10-degrees toward the [121BAR] and [211BARBAR] directions has been measured using LEED. On all the surfaces studied, except 10-degrees toward [121BAR], a weak (2 x 2) ordering occurs in the same temperature range (300-600-degrees-C) as on the flat Ge(111) surface. However the full c(2 x 8) reconstruction of the flat surface does not occur, or appears with very weak intensity, on the vicinal surfaces. At high temperatures, all the vicinal surfaces contain single-layer-height steps of density consistent with the miscut angle. The single-layer-height steps are stable to room temperature for misorientation angles up to 9.8 +/- 0.2-degrees on the surfaces misoriented toward the [211BARBAR] direction. Between 9.8-degrees and 11.4-degrees miscut, these surfaces facet to expose a (5 x 2)-reconstructed (322) facet at approximately 440-degrees-C. Surfaces misoriented toward the [121BAR] direction undergo a step doubling transition over the same temperature range that the (2 x 2) ordering occurs. The low-temperature structure consists of a mixture of single- and double-layer-height steps. Observations on the structure of laser-quenched surfaces are also reported.