Field emission proporties of copper nanocones grown in polymer ion-track membranes

Copper nanocones (Cu-NCs) of about 30 μm length and of ~2.4 μm in base and ~380 nm in tip diameter were grown in polymer ion-track membranes. Field emission (FE) properties of two types of cathodes with randomly distributed Cu-NCs were investigated. The unstructured cathode with high number density (107 cm^-2) and excellent mechanical stability of Cu-NCs yielded stable currents up to 100 μA at electric fields of about 100 V/μm as measured with an anode of 30 μm in diameter. The structured cathode with triangular patch array of less Cu-NCs (<; 10⁶ cm^-2) provided well-aligned FE with about 90% efficiency at much reduced onset field levels (~20 V/μm) but lower current limits, too. SEM images of the random Cu-NCs after current processing revealed only slight changes of the tip morphology. The actual status and further optimization steps of structured Cu-NC cathodes for device applications will be discussed.