In this book we have discussed the fabrication of self organised nanostructures on the surfaces of GaAs(100) as well as of Si(100) using energetic ion beams. For the case of GaAs(100),role of altered surface composition has been investigated to understand the growth evolution of ripples and nanodosts on the surface.The deeper understanding on the origin of ripples was developed on Si(100) semiconductor as a function of ion beam parameters. Stress induced solid flow inside the amorphous layer is studied in ripple patterning. And, the importance of amorphous/crystalline (a/c) interface in the surface patterning is summarized as a function of ion fluence.