Surface nanostructures induced by slow highly charged ions on CaF2 single crystals

We present first results on the generation of surface nanostuctures by slow HCI on cleaved CaF2 (111) surfaces. The CaF, single crystals were irradiated with slow (v << 1 a.u.) Xe44+ HCI from the Heidelberg-EBIT. Like for other ionic fluoride single crystals, ion-induced surface structures in CaF2 are known to be stable in atmospheric conditions at room temperature. After irradiation the crystals were investigated by scanning force microscopy. Topographic images reveal the generation of nanometric hillocks protruding from the surface. The number of hillocks per unit area is in agreement with the applied ion fluence. A discussion of the role of the potential energy as well as a comparison with observations for swift heavy ion irradiations of CaF2 single crystals are presented. (c) 2006 Elsevier B.V. All rights reserved.