{311} facets of selectively grown epitaxial Si layers onSiO2-patterned Si(100) surfaces

A Si epitaxial layer was selectively grown on ${\mathrm{SiO}}_2$-patterned Si(100) with no miscut and on 1°, 3°, and 4° miscut vicinal surfaces by ultrahigh-vacuum chemical-vapor deposition using disilane. On the patterned Si(100) surfaces with and without miscuts, faceted (100) layers grew. Although {111} is energetically the most stable surface, the resulting facets had {311} orientation. This means that the {311} faceting is related to the growth kinetics rather than the energetics. Macroscopically, the {311} faceting is caused by the slower growth rate of the (311) surface than that of the (100) surface. On the vicinal surfaces, the top surface of the selectively grown layer was not vicinal but had exactly (100) orientation. This indicates the ready incorporation of adatoms into the step edges of (100) terraces and the subsequent step-flow growth mode. When the flowing step reaches the end of the top surface, it is swallowed into the facet and disappears. This decreases the step density and makes the vicinal surface flat. With respect to the swallowing of the growing steps at the facet corner, we propose a microscopic model for the {311} faceting.