Variation in the thicknesses of amorphous layer during ripple evolution on Si surface by 50 keV Ar+ ion bombardment has been studied as a function of ion fluence. Atomic force microscopy demonstrates the formation of ripples with ion beam irradiation. Cross-sectional transmission electron microscopy (XTEM) study shows that the ripple microstructure consists of thicker amorphous layer on the front slope, whereas comparatively thinner amorphous layer on the rear slope. This observation of a thicker amorphous layer on the front of ripples as compared to their rear sides is quite common. However, the fluence dependence study on the thickness variation is not reported so far. A detailed analysis of the stationary cross-sectional area of amorphous layer shows that the incompressible solid flow plays a dynamical role in the thickness variation of amorphous layer during ion beam induced patterning of the solid surfaces. The variation in thickness of amorphous layer is also verified by Micro-Raman investigations. Rutherford back scattering experiment was performed to confirm the argon (Ar) incorporation in the near surface region of silicon samples. (C) 2013 Elsevier B.V. All rights reserved.