In adsorption on Si(112) and its impact on Ge growth

The change of the Si(112) surface morphology and structure induced by In adsorption, as well as the impact of In preadsorption on the growth kinetics and island morphology in Ge/Si(112) epitaxy, has been investigated by means of low-energy electron microscopy and diffraction. The intrinsically faceted Si(112) surface is smoothed upon In saturation. In contrast to a previously reported (7
$\times$
1) reconstruction (reported in a recent work of Gai et al.), we observe a
$[(3 + x) \times 1]$
superstructure, with
$x \approx 1/2$
. This is attributed to the coexistence of (3
$\times$
1) and (4
$\times$
1) building blocks with In vacancies. The presence of such vacancy rows is confirmed by the saturation of the
$[(3 + x) \times 1]$
structure at about 0.8 monolayers. Ge growth on In-saturated Si(112) leads to the formation of 3-D islands, the morphology of which depends on the growth temperature. At 450
$^{ \circ}\hbox{C}$
, isotropic and dashlike islands are observed, whereas at 500
$^{\circ}\hbox{C}$
, larger islands with a triangular outline are found. The orientation of the side facets of these triangular islands have been identified to be (111), (013), and (103). The dependence of the island density on the growth temperature indicates an enhanced Ge surface diffusion, as compared with growth on bare Si(112).