MORPHOLOGY OF THIN NACL FILMS GROWN EPITAXIALLY ON GE(100)

A LEED profile analysis of NaCl films grown epitaxially on Ge(100) was carried out in order to determine the morphology of these films. Films of 3 and 8 double layers thickness were analysed. Due to steps of monatomic height of the Ge substrate, which do not fit to the NaCl lattice, the NaCl lattice is elastically strained over many lattice constants forming an elastic ''carpet'' across these steps. Far away from these steps the films are in registry with the Ge substrate. This model describes quantitatively the measured beam profiles, as tested both by analytic calculations and by computer simulations, and correctly predicts an increase of the strained areas as a function of film thickness.