Single and polycrystalline Si1-xGex samples have been bombarded using low energy oxygen ions to study the change in their surface morphologies and ripple formation. Both strained, relaxed and polycrystalline Si1-xGex samples grown on Si(0 0 1) were used to study the effect of crystallinity on ripple formation. Bombardment by 1 keV oxygen ions shows completely different morphologies for the different samples under identical experimental conditions. Ripples on Si1-xGex samples appear much earlier than in Si. Moreover, the nature of the ripples for the polycrystalline sample is markedly different from those of the single crystals. The ripples on relaxed samples are greatly influenced by the location of the dislocation lines on the sample surface. The observations clearly show that rippling is affected not only by the layer constituents but also by its crystallinity and presence of regular structures that favour rippling in a specific direction. (C) 2008 Elsevier B.V. All rights reserved.