We have deposited a 12 nm thick Ge layer on Si(1 0 0) held at 200 degrees C by thermal evaporation under high vacuum conditions. Upon subsequent thermal annealing in vacuum, self-assembled growth of nanostructural Ge islands on the Ge layer occurred. Atomic force microscopy (AFM) and grazing incidence small-angle X-ray scattering (GISAXS) were used to characterize such layers. GISAXS measurements evidenced the formation of cylinder shaped structures upon annealing at 700 degrees C, which was confirmed by AFM measurements with a very sharp tip. A Ge mass transport from the layer to the islands was inferred by X-ray reflectivity and an activation energy of 0.40 +/-0.10 eV for such a process was calculated. (c) 2006 Elsevier B.V. All rights reserved.