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. Film s of 3 and 8 double layers thickness were analysed. Due to steps of mo natomic height of the Ge substrate, which do not fit to the NaCl latti ce, the NaCl lattice is elastically strained over many lattice constan ts forming an elastic ''carpet'' across these steps. Far away from the se steps the films are in registry with the Ge substrate. This model d escribes quantitatively the measured beam profiles, as tested both by analytic calculations and by computer simulations, and correctly predi cts an increase of the strained areas as a function of film thickness.