Surface erosion of a strained Si0.8 Ge0.2 epilayer by 500 eV Ar+ ions with a fluence of 4×1017 ions/cm2 and the transformation from crystalline ripples to elongated Ge islands are reported by aligning the beam from 69° to 50° from the surface normal. Crystalline nature and the near surface Ge enrichment in such ripple structures are revealed by transmission electron microscopy. Moreover, ion beam induced decomposition of the SiGe network and the appearance of dislocation bands by suppressing the near-bandgap emission are manifested by μ -Raman and photoluminescence studies, respectively. © 2010 American Institute of Physics.