Ion bombardment induced self-organization on silicon

The ongoing miniaturization in high-technology applications, especially in the case of opto-electronic devices and ultra-high density storage media, demands for efficient ways to fabricate large-area arrays of nanoscale structures. Besides efforts to develop advanced lithography methods with lateral structure sizes less than 100 nm and scanning probe microscopy assisted techniques an elegant way is utilizing the self-organization on solid surfaces to fabricate nanoscale structures. In the past few years self-organization of nanostructures as surface ripples and three- dimensional crystallites has been intensively studied during growth of thin films under stress. Self-organization may also happen during atom removal by ion bombardment of single crystal surfaces. Under certain bombardment conditions this technique results in the formation of ripples as well as regular patterns of pits and pyramids. The latter case has not yet been observed on semi-conductor surfaces, so far. The aim of the project is a systematic study of surface roughness evo-lution during ion bombardment of silicon (001), the technologically most relevant semiconductor surface, to search for and understand bombardment induced self-organization of Si nanostructures. For this purpose we plan ion bombardment experiments in conjunction with atomic-force micros-copy measurements (AFM) to investigate the surface roughness evolution of ion bombarded Si(001) surfaces for a wide range of bombardment parameters as ion energy, angle of ion inci-dence and substrate temperature. Special emphasis will be given to the use of different noble gas ion species and a variation of substrate vicinality in order to explore the influence of surface and subsurface strain on the pattern formation. For a quantitative characterization of the bombardment induced surface morphologies, one- and two-dimensional correlation function and power spectral density analysis will be applied to the AFM images. By this way, surface roughness parameters as well as integral information on average size and separation, size distribution, shape and anisotropy of the nanostructures are obtained. Based on the morphological data and their dependencies on bombardment and sample parameters, the underlying mechanisms of the self-organization shall be explored. The results would not only contribute to a better understanding of ion bombardment induced nanostructure formation but would also open the route to a novel fabrication technique of large-area nanostructured surfaces.