Effect of dispersion on the nanoscale patterns produced by ion sputtering

Our simulations show that dispersion can have a crucial effect on the patterns produced by oblique-incidence ion sputtering. It can lead to the formation of raised and depressed triangular regions traversed by parallel-mode ripples, and these bear a strong resemblance to nanostructures that are commonly observed in experiments. In addition, if dispersion and transverse smoothing are sufficiently strong, highly ordered ripples form. Finally, dispersion can cause the formation of protrusions and depressions that are elongated along the projected beam direction even when there is no transverse instability. This may explain why topographies of this kind form for high angles of ion incidence in cases in which ion-induced mass redistribution is believed to dominate curvature-dependent sputtering.