Impact of Slow Highly Charged Ions on Insulating Surfaces

Surface modifications induced by the irradiation with ions have been investigated for long time. Depending on their energy the ions create a crater resulting from nuclear sputtering or can induce the formation of hillocks at high kinetic energies. For highly charged ions (HCI) the situation is more complex. In addition to their kinetic energy HCI posses also potential energy which is the sum of the ionization energies to create them. This large amount of potential energy is released when interacting with solids and deposited into a small volume close to the surface. The resulting high excitation can thus induce various effects, like secondary electron emission, potential sputtering, and finally also permanent surfaces modifications [1].
Systematic investigations of surface modifications induced by highly charged ion on different materials have revealed many interesting mechanisms. On CaF2 surfaces hillock structures are formed by the impact of HCI due to a localized phase transition [2]. In the case of the alkali halide crystal KBr the formation of nanostructures results from the desorption of surface atoms from a single ion impact site [3]. In both cases a threshold in the potential energy for the formation of the structure has been identified and could be interpreted in the frame of the applied models. However, still a unified picture of these effects is missing.
This work has been supported by the European Project ITSLEIF (RII3#026015).
[1] S. Facsko, R. Heller, A. S. El-Said, W. Meissl and F. Aumayr, J. Phys.: Cond. Matter 21, 2240122 (2009) .
[2] A. S. El-Said, R. Heller, W. Meissl, R. Ritter, S. Facsko, C. Lemell, B. Solleder, I. C. Gebeshuber, G. Betz, M. Toulemonde, W. Moller, J. Burgdorfer and F. Aumayr, Phys. Rev. Lett. 100 237601 (2008).
[3] R. Heller, S. Facsko, R. Wilhelm, and W. Möller, Phys. Rev. Lett. 101, 096102 (2008).