Characterization of track-etched membranes by small-angle x-ray scattering

Track-etched membranes are polymer foils irradiated with swift heavy ions and subsequently wet-etched to create pores by dissolving defects formed along the ion trajectories. Under suitable conditions, the resulting pores are of cylindrical shape and uniform in size. Such membranes are commonly used for filtration or as templates for nanowires, grown inside the pores, e.g., by electrochemical deposition. The aim of this project is to compare nanometric pores in different polycarbonate (PC) foils and to study the effect of UV treatment. UV exposure of ion-irradiated polymers prior to chemical etching is a sensitization process widely used to improve the size distribution of pores. The experiments were performed with two different types of amorphous PC foils (30 μm Makrofol N, 20 μm LOFO) irradiated at the UNILAC with Xe ions of 11.1 MeV/u and fluences between 3×10, and 10 ions/cm. Prior to etching, some of the samples were exposed to UV light (1 h from each side). Track etching was carried out in 5 M NaOH at 60 °C for 3, 5 and 8 min. Ion-irradiated and etched membranes were analysed by small-angle x-ray scattering (SAXS) at the ID01 line of the ESRF synchrotron in Grenoble. SAXS is a nondestructive method probing large pore ensembles with a single measurement and providing three-dimensional pore information in the bulk [1], in contrast to typical microscopy techniques (e.g. scanning electron or force microscopy) that are limited to the sample surface.