HREM INVESTIGATION OF LATENT TRACKS IN GES AND MICA INDUCED BY HIGH-ENERGY IONS

Observations of heavy ion latent tracks in layered materials were carr ied out with a 400 kV high resolution electron microscope as well as w ith conventional 100 and 200 kV microscopes. The materials were irradi ated normal to the cleavage plane at the UNILAC-accelerator at GSI Dar mstadt with ions up to several MeV/u. High-resolution images of latent tracks in muscovite mica and in GeS single crystals are presented in this paper. The micrographs show that the track core represents a diso rdered zone. Depending on the diffraction conditions in the surroundin gs of the tracks, strain contrast centres are visible. The boundary be tween the amorphous track core and the intact crystal lattice is well defined. The cross sections of the tracks in mica have a nearly circul ar shape. In contrast to that they are elliptical in GeS and are well oriented with respect to the crystal lattice. The sharp amorphous-crys talline transition allows the exact measurement of the track dimension s. The values resulting for the track diameters show a large variation in size depending on the ion sort. The tracks produced by heavy ions have more than twice the diameter of those produced by light ions. Rel ations between the track size and the energy loss for different ions a re given, (C) 1998 Elsevier Science B.V. All rights reserved.