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

We show that germanium dots can be directly grown by molecular beam epitaxy (MBE) on a silicon (001) surface covered by a thin (1.2-nm-thick) thermal silicon oxide layer. We describe the experimental procedure, which induces the growth of a high density (10(11)/cm(2)) of nanometric germanium dots on silicon oxide. Germanium dots grown by MBE exhibit an epitaxial relationship with the underlying silicon substrate. We show that despite the presence of the thin silicon oxide layer, the silicon grown to embed the germanium dots is also single crystal in epitaxy with the silicon substrate. Nanometric size high-density crystalline inclusions in silicon oxide, seen in high-resolution transmission electron microscopy observations, are tentatively proposed as nucleation seeds for germanium dots and silicon lateral overgrowth on silicon oxide. (C) 2000 American Institute of Physics. [S0003-6951(00)02748-0].