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It is well known that low energy ion beam erosion is a versatile tool for pattern formation on different materials. For example, ripple as well as dot patterns were observed on Si surfaces during low energy ion beam erosion. Due to the simplicity of the method, and the possibility to produce large-area nanostructured surfaces the process offers an alternative, simple and cost-efficient route for nanostructuring of surfaces. However, usually this self-organization process lacks long-range order due to the formation of domains and defects in the pattern. One possibility to influence the ordering of structures is by using pre-patterned substrates. In this way due to spatial limitations and guided by the lateral ordering of the pre-patterned templates the evolving topography shows an improved ordering, a fabrication principle also known as guided self-organization. The method allows also an exact positioning of nanostructures on the surface.
In this contribution results on the ripple and dot pattern formation on pre-patterned Si surfaces during low energy (≤ 2000 eV) Kr+ and Xe+ ion beam erosion are presented. The experiments are performed at normal and oblique ion incidence with and without sample rotation, at room temperature. The pre-patterned substrates are fabricated by various lithographic techniques in combination with etching techniques for structure transfer. Depending on the shape of the pre-patterned structure different results are obtained. The formation of nanostructures depends on the local incidence angle, local orientation and curvature of the surface. These characteristics of the local topography influence the forming type of nanostructures, the degree of ordering and the varying orientation of nanostructures with respect to the direction of incident ion beam. For example it will be shown that curved ripples can evolve, where the curvature is caused by a continuous change in the local topography within pre-patterned regions. In general, it is demonstrated that the combination of conventional lithographic techniques with ion beam induced self-organization offers simultaneous patterning on different length scales, a perfect lateral ordering and an exact positioning of nanostructures.
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