In this paper, we report on evolution of ripple morphology on Si(1 0 0) surface due to 60 keV Ar+-ion implantation to the fluence of 2 x 10(18) ions cm(-2) and over a large incident angular window of 0-75 degrees. Room temperature implantations were carried out by using a uniform current density of 20 mu A cm(-2). Atomic force microscopic (AFM) studies indicate that ripple morphology starts to appear at an incident angle 45 degrees and becomes more prominent at higher incident angles. AFM studies also reveal that while the ripple wavelength decreases with increasing angle of incidence, the amplitude increases with the same. We also observe a systematic variation in the surface roughness with incident angle. Micro-Raman studies show that the sub-surface silicon layer becomes amorphous whose depth keeps reducing at higher incident angles. The results are attributed to viscous flow mechanism. (C) 2011 Elsevier B. V. All rights reserved.