MeV-atomic-ion-induced tracks on the surface of CaF2 single crystal

Tracks induced by high-energy Pb and Xe ion impacts were studied on the surface of CaF2 single crystals by shadow replica electron microscopy. Irradiation angles of 1° and 2° with respect to the surface plane were used. Lengths and widths of two kinds of tracks were compared: (1) the surface tracks formed on the bare crystal surfaces and (2) the island tracks formed on the crystal surfaces coated by gold islands. In addition, upper and lateral collectors were applied in order to estimate the fraction of islands removed intact from the coated surface areas. Collector surfaces were studied by electron microscopy and scanning force microscopy. Comparing the present observations on CaF2 to the results obtained on LiF we proposed a scheme to explain how the track formation process is influenced by the physical characteristics of these two ionic crystals.