Nanostructuring surfaces by ion sputtering

Surface etching by ion sputtering can be used to pattern surfaces. Recent studies using the high-spatial-resolution capability of the scanning tunnelling microscope revealed in fact that ion bombardment produces repetitive structures at nanometre scale, creating peculiar surface morphologies ranging from self-affine patterns to 'fingerprint'-like and even regular structures, for instance waves (ripples), chequerboards or pyramids. The phenomenon is related to the interplay between ion erosion and diffusion of adatoms (vacancies), which induces surface re-organization. The paper reviews the use of sputter etching to modify 'in situ' surfaces and thin films, producing substrates with well defined vertical roughness, lateral periodicity and controlled step size and orientation.