Epitaxial growth of germanium dots on silicon (001) surface covered by a very thin dielectric layer

In this paper, we report the molecular beam epitaxy of germanium dots on Si (001) surface covered by an ultra-thin (12–20 Å thick) dielectric layer. Despite the presence of a dielectric layer, the germanium dots exhibit an epitaxial relationship with the underlying silicon substrate. The structural properties of germanium dots grown on Si (001) surface covered by a thin layer of SiO2 and on Si (001) surface covered by a thin layer of Si3N4 are discussed. The characterisation of dielectric layers and germanium dots was performed using reflection of high-energy electron diffraction, atomic force microscopy (AFM) and high-resolution transmission electron microscopy (HRTEM). The atomic force microscopy results show that the Ge dots have a hemispherical shape with 10 nm average size and that the density of dots is as high as 2–5×1011 cm−2.