First-principles study of strain stabilization of Ge(105) facet on Si(001)

Using the first-principles total energy method, we calculate surface energies, surface stresses, and their strain dependence of the Ge-covered Si 001 and 105 surfaces. The surface energy of the Si 105 surface is shown to be higher than that of Si 001 , but it can be reduced by the Ge deposition, and becomes almost degenerate with that of the Ge/Si 001 surface for three-monolayer Ge coverage the wetting layer , leading to the formation of the 105 -faceted Ge hut. The unstrained Si and Ge 105 surfaces are unstable due to the large tensile surface stress originated from the surface reconstruction, but they can be largely stabilized by applying an external compressive strain, such as by the deposition of Ge on Si 105 . Our study provides a quantitative understanding of the strain stabilization of Ge/Si 105 surface, and hence the formation of the 105 -faceted Ge huts on Si 001 .