Study of heavy-ion induced modifications in BaF2 and LaF3 single crystals

BaF2 and LaF3 single crystals were irradiated with different ions from Ne to U having energies between 1.4 and 13.3 MeV/u and were subsequently analyzed with scanning force microscopy (SFM), optical spectroscopy and surface profilometry. Similar to numerous other ionic crystals, ion-induced hillocks were observed by SFM, the mean size on the nanometer scale depending on the electronic energy loss. BaF2 shows optical color-center absorption spectra, which consist of broad bands ascribed to F-center aggregates, whereas LaF3 does not exhibit any specific absorption bands. Depending on the beam parameters (energy, fluence, etc.), the irradiation of both crystals leads to more or less pronounced out-of-plane swelling. In order to study the thermal behaviour of ion-induced modifications, isochronal annealing has been performed. Both crystals show a decrease of the relative step height and the areal density of the hillocks with increasing temperature. (C) 2004 Elsevier B.V. All rights reserved.