High temperature growth of Ag phases on Ge(111)

Abstract

The growth of the (3 Â 1) and (ͱ3 Â ͱ3)R30 phases of Ag on Ge(111) on substrates at temperatures from 540 to 660 C is characterized with low energy electron microscopy (LEEM) and low energy electron diffraction (LEED). From 540 C to the Ag desorption temperature of 575 C, LEEM images show that growth of the (3 Â 1) phase begins at step edges. Upon completion of the (3 Â 1) phase, the (ͱ3 Â ͱ3)R30 phase is observed with a dendritic growth morphology that is not much affected by steps. For sufficiently high deposition rates, Ag accumulates on the sample above the desorption temperature. From 575 to 640 C, the growth proceeded in a manner similar to that at lower temperatures, with growth of the (3 Â 1) phase to completion, followed by growth of the (ͱ3 Â ͱ3)R30 phase. Increasing the substrate temperature to 660 C resulted in only (3 Â 1) growth. In addition, for samples with Ag coverage less than 0.375ML, LEEM and LEED images were used to follow a reversible phase transformation near 575 C, between a mixed high coverage phase of [(4 Â 4) þ (3 Â 1)] and the high temperature, lower coverage (3 Â 1) phase.