The diffusion process on Si (001) in the presence of a 5keV Ar+ ion beam was investigated by monitoring the initiation of ripple-pattern formation. The morphology of the surface obtained by scanning tunnelling microscopy measurements in ultra-high vacuum were characterized by using the height-difference correlation function. These measurements clearly revealed the formation of nanostructured ripple patterns having a wavelength of ~60nm and a height of ~0.32nm at 200C. The results demonstrated that ion beam induced and thermal diffusions could not be treated as additive processes and the observed enhancement of surface diffusion required a lowering of the activation energy that arose due to the creation of ion-beam induced vacant regions.

Enhanced Surface Diffusion in Forming Ion-Beam-Induced Nanopatterns on Si (001). R.Banerjee, S.Hazra, M.K.Sanyal: Journal of Physics D, 2008, 41[5], 055306 (4pp)