SURFACE-STRUCTURES OF PB ON GE(001) OBSERVED BY SCANNING-TUNNELING-MICROSCOPY

The different structures of Pb on Ge(001) have been studied as a funct ion of Pb-coverage and annealing temperature. At low coverages a new ( 2 x 2) reconstruction was found which is similar to that of several ot her group-III and group-IV adsorbate structures on Si(001). A structur al model for the c(4 x 8) phase is presented, which explains the appea rance of the c(4 x 8) c(2 x 4) domain boundaries. Evidence for the exi stence of a (1 x 1) layer in the (5 x 1) reconstruction and of dimer r ows in the (2103) reconstruction is given. The incommensurate (4 x 1)i phase is shown to consist of distorted c(4 x 8) unit cells.