GROWTH-MECHANISM AND MORPHOLOGY OF GE ON PB COVERED SI(111)SURFACES

We study the mechanism and surface morphology in epitaxial growth of G e on Pb covered Si(lll) using a scanning tunneling microscope (STM). W e find that Ge adatoms have a very large diffusion length at room temp erature. The growth is close to perfect layer-by-layer for the first t wo bilayers. Surface roughness increases gradually with the film thick ness, but no 3D islands are found at room temperature. For growth at s imilar to 200 degrees C, 3D Ge islands appear after completion of the second bilayer. At room temperature, we believe, the Pb layer enhances surface diffusion and the descending-step motion of Ge adatoms, but t he ascending-step motion is hindered and thus 3D island growth is supp ressed. (C) 1998 Elsevier Science B.V. All rights reserved.