In situ investigation by GISAXS and GIXD of the growth mode, strain state and shape of Ge islands during their growth on Si(001)

The growth mode, strain state and shape of Ge islands were analyzed in situ, during their growth on Si(0 0 1), by combining grazing incidence small angle X-ray scattering (GISAXS) and X-ray diffraction (GIXD) measurements. GISAXS measurements provide the detailed evolution of the shape of the grown quantum dots (QDs) and allow characterizing the degree of ordering. GIXD allows monitoring the island nucleation, the evolution of the in-plane size and the epitaxial orientation of the QDs, as well as the diffusion of the wetting layer into the islands during growth. It is found that for a deposition temperature of 500 °C, an amount of about one atomic layer is transported from the four monolayers (ML) thick wetting layer into the 3D islands.