Ripple rotation, pattern transitions, and long range ordered dots on silicon by ion beam erosion

The importance of the ion incidence angle in self-organized pattern formation during low energy Xe+ ion beam erosion of silicon is elaborated. By a small step variation of the ion incidence angle, a variety of nanostructured patterns can develop. In this context, the angular distribution of ions within the ion beam is explored as an additional parameter controlling the evolution of the surface topography. Due to a controlled variation of these two parameters, hitherto unknown phenomena are found: (i) formation of rotated ripples, (ii) continuous transitions between patterns, and (iii) long range square ordered dot pattern.