Structure transition of Ge/Si(1 1 3) surfaces during Ge epitaxial growth

It is observed that a Ge wetting layer on Si(1 1 3) changes its surface structure from an initial Si(1 1 3)-3×2 to Ge/Si(1 1 3)-3×2+3×1, Ge/Si(1 1 3)-3×2+3×1+2×2, and finally Ge/Si(1 1 3)-2×2 for a few-ML epitaxial growth. It is demonstrated that such transition results from the epitaxial stress evolution. Specifically, the 2×2 confines the epi-layer along the View the MathML source direction by tension and releases compression in the perpendicular direction of the View the MathML source forming trenches. Without reconstruction, the trenches are favorable for adatom nucleation and elongated growth of islands owing to dangling bonds and possible relaxation of the structure along the trenches.