Thermal annealing-induced modification of the structure and electrical conductivity of metallic nanotubes embedded in PET track-etched membranes

This work is dedicated to developing a simple methodology that allows for the application of a thermal annealing process, which can improve the conductivity of metallic nanostructures, embedded in porous track-etched membranes based on polyethylene terephthalate (PET TeMs), but at the same time, does not compromise the mechanical properties. Zinc, copper, and cobalt nanotubes (NTs) prepared by electrochemical deposition in PET TeMs were annealed at 200 degrees C for different time periods. The effects of annealing treatment on the structural and electrical properties were investigated by scanning electron microscopy, X-ray diffraction, and room-temperature resistance measurements. Choosing the appropriate annealing time for Zn or Cu-NTs allows controlling the formation of an oxide phase in these nanostructures. The presence of the oxide phase in an amount of no more than 10-15 wt% led to a decrease in the resistivity and an increase in the conductivity. Thermal annealing of Co-based NTs changed intensities of the metastable fcc beta-Co and stable hcp alpha-Co phases. The metastable beta-Co phase caused additional defects due to a change in the crystallite size after 90 min of thermal annealing.