Structure and phases of In on Ge(001)

The two-dimensional phases of In on Ge(001) have been studied with scanning tunnelling microscopy and electron diffraction. STM images of the Ge(001)(2 X 2)-In reconstruction are similar to those of the (2 X 2) reconstructions induced by other group-III and group-IV adsorbates on Si(001) and Ge(001). The reconstructed surface is terminated with 0.5 ML dimerized metal atoms. The mixed (3 X 3) + (4 X 3) phase at higher coverage consists of pairs and triplets of identical In-rich subunits. Annealing samples with a coverage of above 1 ML at a temperature of similar to 200 degrees C results in the formation of a well ordered (5 X 4) reconstruction while at a temperature of similar to 350 degrees C the surface facets. The resulting (103) facets form a regular lattice with long-range order. The (n X 4) reconstruction on annealed samples at about 0.6 ML coverage can be described as a regular stacking of (3 X 4) and (4 X 4) subunits.