Copper nanocones grown in polymer ion-track membranes as field emitters

Abstract

Field emission (FE) properties of unstructured and patch-structured cathodes with randomly distributed and vertically aligned copper nanocones (Cu-NCs) are reported. The cones of ~28 μ m height, 2.4 μ m base diameter and 95–220 nm tip radius were fabricated by electrochemical deposition of Cu into conical channels of heavy-ion-irradiated and asymmetrically etched polycarbonate membranes. FE measurements of the unstructured cathodes with slowly-grown Cu-NCs of high number density (10 7 cm −2 ) and excellent mechanical stability yield stable currents up to 280 μ A from an emission spot of 30 μ m. For the structured cathodes with a triangular patch array of less dense Cu-NCs ( 6 cm −2 ), well-aligned FE with ~90% efficiency is reproducibly achieved. A trade-off between low onset field (~22 V/ μ m) for sparsely grown Cu-NCs with sharp tips and high current limit (~100 μ A) for densely grown ones with broader tips is observed. Possibilities for further optimization of such field emitters for cold cathode applications are discussed.