Ripple rotation on ion sputtered Si (100)

Controllable process of ion sputtered rippling is of significance for the generation of nanostructures on technologically important Si surface. Si(100) was irradiated with 30 kV focused Ga+ ions at various incidence angles. It was found that ripple only formed at 30° incidence angle. At low ion dose, ripple with wavelength of 400 nm was oriented perpendicular to the ion beam direction. However ripple with larger wavelength of 1 μm was rotated with increasing ion dose. The orientation of rotated ripple was observed to be still dependent on the ion beam direction. Such rotated ripple structures can be explained by the nonlinear sputter patterning model.

► Ripple is observed on Ga+ irradiated Si surface only at 30° incidence angle.
► Ripple orientation is rotated with increasing sputtering time.
► The results provide experimental support to the nonlinear theoretical model.