Thermally stable and anisotropically conducting membranes consisting of sub-micron copper wires in polyimide ion track membranes

Hybrid membranes consisting of polyimide (PI) films embedded with copper wires were prepared by electroplating copper into the etched pores of ion track membranes. 12 μm thick polyimide films were irradiated with 129Xe23+ ions with an energy of 3.5 MeV/n and fluences ranging from 3.0 × 103 to 3.0 × 108 ions/cm2. The films were etched with sodium hypochlorite solution to open ion track through holes of 0.2–2.9 μm in diameter, in which copper wires were deposited by electrochemical plating to prepare thermally stable hybrid membranes that have anisotropic conductivity in the direction normal to the film plane. It was possible to estimate electrical resistance of single copper wire by reducing the ion fluence, which corresponded fairly well with the value estimated from the bulk resistivity. It was also found that the resistance, as well as the hybrid membrane structure, remains stable against thermal treatment of at least up to 400 °C. Such anisotropic conducting membranes with high thermal stability are expected to have wide application in microelectronics devices.