Morphology of track cores and halos created by swift uranium ions in polycarbonate

A small-angle X-ray scattering study of ion damage trails, latent ion tracks, created through a 60-μm thick polycarbonate foil by penetrating 2.64 GeV U ions, has revealed density decreases of 69% along 5.8-nm diameter track cores, and low concentration of 8-nm diameter bubbles that reside in the surrounding track halos. We attribute track formation to spatially confined radiolysis and subsequent release of gaseous and volatile alteration products. Radiolysis is undoubtedly activated by primary reactive species formed upon ion-energy deposition. With the recently observed similar open structure of U-ion track cores in polyimide, it is likely that the technologically important porous structure is a common characteristic of polymeric ion tracks.