We investigate and elucidate the surprising observation of atomically
ordered domains in dome-shaped SiGe nanoislands. We show, through
atomistic Monte Carlo simulations, that this ordering is
a surface-related phenomenon, and that is driven by surface equilibrium
rather than by surface kinetics. The ordering depends on facet
orientation. The main source of ordering is the { 15 3 23 } facet,
while the {105} and {113} facets contribute less. Subsurface ordered
configurations self-organize under this facet and are frozen-in
and buried during island growth, giving rise to the ordered domains.
Ordering mechanisms based on constrained surface kinetics,
requiring step-mediated segregation at the island facets,
are shown to be much less likely.

From: G. Vantarakis, I. N. Remediakis, and P. C. Kelires,
“
Ordering Mechanisms in Epitaxial SiGe Nanoislands”
Physical Review Letters
108, 176102 (2012).