Formation of nanopore membranes and nanowires by high energy ion irradiation of polymer foils

Foils of polyimide and polycarbonate were irradiated with highly energetic heavy ions, such as gold and lead. The latent ion tracks in the polymer are cylinders of radiation damage. Along them, the polymer can be chemically etched. Cylindrical pores are created. Thus, nanopore membranes with pores with diameters around 100 nm can be fabricated. The areal pore density corresponds to the ion fluence, and the pore diameter depends on the chemical etching conditions. The nanopore membranes can be used for separating gas mixtures. This is demonstrated with mixtures of CO and CO2. In a second step, the nanopores can be galvanically filled with metal. By removing the polymer matrix, nanowires can be gained. Their shape depends on the pore shape, and their microstructure depends on the galvanic growth conditions. Nanowires of copper, permalloy, and gold were fabricated. They were investigated by scanning electron microscope for their diameter and shape. The nanowires with diameters from 70 nm to 300 nm were cylindrical with a smooth contour. For the gold nanowires, it is demonstrated that they can be grown both poly- and single crystalline, depending on the galvanic growth conditions.