INITIAL-STAGES IN THE EPITAXIAL-GROWTH OF NACL ON GE(001)

We have performed an in situ X-ray scattering study of the initial stages of NaCl/Ge(001) heteroepitaxy. The c(4 x 2) surface reconstruction, characteristic of Ge(001) at low temperature, is suppressed immediately upon deposition of NaCl. However, the (2 x 1) symmetry of the surface unit cell is preserved, even after 6 monolayers (ML) of NaCl have been grown. Analysis of the in-plane, half-integer Bragg reflections, specific to the surface reconstruction, supports a model in which the Ge dimer remains and sodium is adsorbed in the ''valley'' site. Subsequent growth of NaCl on the modified surface occurs through the formation of islands with the thickness of a triple layer (3 ML), which fill in until the triple layer is complete.