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Abstract:
We investigate the morphological evolution of islands obtained by
epitaxial growth of Ge on Si(001) substrates. We are able to obtain
highly uniform distributions of SiGe islands, which exhibit a "barn"
shape. In addition to previously observed facets, we identify higher
index facets, which are not observed in dome-shaped islands. The
evolution of the island-related facet area provides evidence of a
transition from domes to steeper barns, which continues the sequence of
coherent island types before the onset of plastic relaxation. For
higher Ge coverages, when plastically relaxed islands (superdomes)
form, the island ensemble loses its homogeneity. This is essentially
the result of anomalous coarsening, with material being transferred
from coherent islands to larger superdomes.