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A.S. El-Said, R. Heller, F. Aumayr, S. Facsko:
"Pyramidal pits created by single highly charged ions in BaF₂ single crystals";
Physical Review B, 82 (2010), 0334031 - 0334034.

In various insulators, the impact of individual slow highly charged ions eV-keV creates surface nanostructures,
whose size depends on the deposited potential energy. Here we report on the damage created on a
cleaved BaF2 111 surface by irradiation with 4.5 q keV highly charged xenon ions from a roomtemperature
electron-beam ion trap. Up to charge states q=36, no surface topographic changes on the BaF2
surface are observed by scanning force microscopy. The hidden stored damage, however, can be made visible
using the technique of selective chemical etching. Each individual ion impact develops into a pyramidal etch
pits, as can be concluded from a comparison of the areal density of observed etch pits with the applied ion
fluence typically 108 ions/cm2 . The dimensional analysis of the measured pits reveals the significance of the
deposited potential energy in the creation of lattice distortions/defects in BaF2.