Surface tracks in polymers induced by MeV heavy-ion impacts

Recent results obtained in our group on surface tracks (cratering and plastic deformation) induced by MeV heavy-ion impacts on polymers are briefly summarized in this paper. The morphology and dimensions of the surface tracks are monitored by scanning force microscopy (SFM) as a function of polymer molecular weight, monomer structure and irradiation temperature. 20 MeV Au-197 ions from the Porto Alegre 3 MV Tandem accelerator were used to bombard the surface of different polymer films. Craters are observed on all irradiated polymers and are a manifestation of the surface erosion induced by the MeV ions. The volume of the craters give the total mass sputtered by each MeV ion impact which varied from (1.3 +/- 0.4) x 10(5) u/ion to (2.7 +/- 1.0)x 10(5) u/ion for polystyrene targets of different molecular weights with ions incident at a grazing angle (79 degrees). This figure varies slightly depending on the nature of the macromolecules. Hillocks, plastically deformed zones around the point of ion impact, may also be present on the surface of irradiated films. The appearance or not of such features and the extent of the permanent deformation are found to be dependent on the molecular weight of a given polymer and the irradiation temperature. (C) 1999 Elsevier Science B.V. All rights reserved.