Visualization in an electron microscope of the impact of energetic projectiles in amorphous targets

Crystalline and amorphous NI3B have been irradiated at 300 K with GeV uranium ions and with 30 MeV C-60 fullerene ions. These projectiles deposit a very large amount of energy in the targets via electronic excitation and ionization, which results in the creation of amorphous tracks in the crystalline compound and of 'disordered amorphous' matter lying in the vicinity of the projectile path in I-he initially amorphous target, which is the first state leading to the well-known anisotropic growth of amorphous materials submitted to high electronic excitations. It is shown here that it is possible to directly visualize in an electron microscope the impact of the ions in the amorphous targets. This allows us to compare the sizes of the observed impacts with those of disordered regions that were previously extracted from phenomenological models describing damage creation in amorphous matter and to compare the extension of damaged regions induced in the same compound when bombarded in its crystalline and amorphous forms.