Molecular beam epitaxy of Si and Ge on the stripe-patterned Si (0 0 1) substrates is studied by scanning tunneling microscopy. The stripe patterns consist of one-dimensional etch grooves oriented along different azimuth directions within the Si (0 0 1) surface. During Si buffer growth, the stripe morphology rapidly changes and the side walls of the grooves are transformed into differently inclined low-energy Si facets, depending on the stripe orientation and growth conditions. Subsequent Ge growth drastically changes the surface topography to form energetically favorable {1 0 5} sidewall facets. Depending on the sidewall geometry, Ge nanoislands formed at a coverage of around 5 monolayers nucleate either in the middle of the sidewalls or in the center of the grooves as a result of material accumulation induced by capillary forces and strain relaxation. (c) 2008 Elsevier B.V. All rights reserved.