Surface Nanostructuring by High-Density Electronic Excitations

Controlled and reproducible creation and manipulation of nano-sized structures are prominent goals in modern nanotechnology. Ion beam technology has demonstrated its uniqueness and effectiveness in the synthesis and precise control of nanostructures in various materials. Slow highly charged ions (HCI) are considered as one of the newest and most promising tools for the creation of surface nanostructures. Compared to the broadly applied lithographic methods, this technique has the advantage that each projectile creates an individual damage trail of a few nanometers width. Moreover, it offers new degrees of freedom for the created nanostructure. It also requires no further treatment, which modifies the original surface like electrochemical deposition technique. Furthermore, HCI create the nanostructures on the surface and in the near-surface region without damaging the bulk which is not avoidable if one uses swift heavy ions (SHI). The study of nanostructure formation on surfaces induced by the strong electronic excitations, delivered by HCI, is a relatively new field and still requires a detailed comparison between materials with similar and different properties, in order to develop a more general understanding of the underlying mechanisms. The project aims at studying the creation of surface nanostructures in strontium fluoride (SrF2), magnesium fluoride (MgF2) and lanthanum fluoride(LaF3) single crystals irradiated by slow highly charged ions. Due to the availability of already well-established understanding of the mechanism responsible for nanostructures creation by SHI, the HCI research can benefit a lot from the comparison with SHI. Therefore, some of the samples will be investigated after irradiation with SHI. The physical processes involved in the creation and size control of the observed structures will be studied by applying mainly two theoretical approaches, namely plasma expansion and inelastic thermal spike techniques. The results from the proposed research project are expected to contribute highly to the clear understanding of the mechanisms responsible for the nanometer-scale structural creation induced by slow highly charged ions and swift heavy ions.