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F. Aumayr, A.S. El-Said, R.A. Wilhelm, R. Heller, S. Facsko, C. Lemell, G. Wachter, J. Burgdörfer, R. Ritter:
"Phase diagram for nanostructuring CaF₂ surfaces by slow highly charged ions";
Poster: 25th International Conference on Atomic Collisions in Solids (ICACS-25), Kyoto University, Kyoto/Japan,; 2012-10-24; in: "Book of Abstracts, ICACS-25", (2012), 184.

Slow highly charged ion (HCI) irradiation on insulating surfaces can cause local
changes in the surface morphology, commonly known as nanostructures [1,2]. On CaF2
recent studies [3] showed the creation of nanometer-sized hillocks with a strong
dependence on the potential energy of the impinging HCI. Below a Xe charge state of
q=28 no such hillocks have been found. However, below this threshold for hillock
formation defects are created, which become visible by means of scanning force
microscopy (SFM) only after chemical etching. These results show that a new regime in
the phase diagram of hillock formation exists. For much lower charge states (q<18) and
small kinetic energies (<10 keV) neither hillocks nor etch-pits could be found. An
extended phase diagram for nanostructure formation on CaF2 due to HCI irradiation is
presented and the three obtained phases are discussed in terms of kinetic and potential
energy dependence.