Enhanced surface diffusion in forming ion-beam-induced nanopatterns on Si (0 0 1)

The diffusion process on Si (0 0 1) in the presence of a 5 keV Ar+ ion beam has been investigated by monitoring initiation of ripple-pattern formation. The morphology of the surface obtained by scanning tunnelling microscopy measurements in ultrahigh vacuum were characterized using the height-difference correlation function. These measurements clearly show formation of nanostructured ripple patterns having wavelength ∼60 nm and height ∼0.32 nm at 200 0C. The results demonstrate that ion beam induced and thermal diffusions cannot be treated as additive processes and the observed enhancement of surface diffusion requires lowering of activation energy that arises due to creation of ion-beam induced vacant regions