Study of ion beam induced swelling in fluorite as an inert matrix model

As a model material of fluorite type structure, single crystals of CaF2 were irradiated with various heavy ions (from S-32 to Bi-209) of specific energies between 1 and 12 MeV u(-1). Using a profilometer, out-of-plane swelling was measured by scanning over the border line between irradiated and virgin areas of the sample surface. The step height as a function of the ion fluence exhibits a linear increase in the initial phase and saturates at high fluences. Track radii contributing to the swelling effect are deduced. Above a critical energy loss of about 5 keV nm(-1), the initial swelling rate per incident ion shows two separated regimes. Finally, the response of CaF2 submitted to high electronic energy loss is discussed in combination with earlier track observations by transmission electron microscopy. (C) 2001 Elsevier Science Ltd. All rights reserved.