Porous tracks along wakes of swift uranium ions in polyimide

Abstract

Density decreases of 64% along ∼6-nm-diam ion damage trails, latent ion tracks, created through a 50-μm-thick polyimide foil by penetrating 2.64GeV U ions, have been measured by small-angle x-ray scattering. This first derived morphology is attributed to local polymer degradation under intense electronic energy deposition, and subsequent transport and release of gaseous and volatile alteration products through the low-density tracks. Free volume undoubtedly accelerates preferential through-track permeability of inert and corrosive agents, a property that is important for track applications.