EPITAXIAL CLUSTERS STUDIED BY SYNCHROTRON X-RAY-DIFFRACTION AND SCANNING-TUNNELING-MICROSCOPY

Nanoscale clusters are often formed during heteroepitaxial crystal gro wth. Misfit between the lattice parameter of the substrate and the ads orbate stimulates the formation of regular clusters with a characteris tic size. The well-known ''hut-clusters'' formed during the growth of Ge on Si(001) are a good example of this type. Adsorbates can also pro duce another type of nanocluster; if the surface free energy of a part icular crystallographic plane becomes lower than that of the geometric al surface of the substrate, then the entire surface will break up int o regular arrays of small facets which look similar to the ''hut clust ers''. We demonstrate that X-ray diffraction in combination with scann ing tunneling microscopy can be used to determine the fundamental prop erties of such clusters. (C) 1998 Elsevier Science B.V. All rights res erved.