Spontaneous nanostructural island formation and layer-to-island mass transport in Ge layers on Si(111) surfaces

We have deposited Ge on Br-passivated Si(111) surfaces under high vacuum (H V) conditions at room temperature (RT). Ge has grown in a layer-plus-island growth mode. Atomic force microscopy (AFM) measurements on the as-deposite d samples show the formation of nanostructural islands. On a 500 degrees C- annealed sample, the size and the density of islands increase. High resolut ion X-ray diffraction (HRXRD) and ion channeling experiments show the lack of epitaxial growth. However, Raman spectroscopy measurements show the poly crystallinity of the Ge layer. X-ray reflectivity (XRR) and Raman spectrosc opy results show that the Ge/Si interface is sharp for the as-deposited lay er and there is no significant intermixing even in the annealed samples. AF M, XRR and Raman spectroscopy results, taken together, indicate mass transp ort from the Ge layer to Ge islands. The temperature dependence of this mas s transfer provides effective activation energy of 0.45 +/- 0.04 eV. (C) 20 00 Elsevier Science B.V. All rights reserved.