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

¹ FB C Physics Department, University of Wuppertal, 42097 Wuppertal, Germany
² Materials Research, GSI Helmholtz Centre for Heavy Ion Research, 64291 Darmstadt, Germany

^a e-mail: serbun@physik.uni-wuppertal.de

Received: 16 December 2011
Revised: 23 February 2012
Accepted: 29 February 2012
Published online: 23 March 2012

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 μm height, 2.4 μm 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 (10⁷ cm⁻²) and excellent mechanical stability yield stable currents up to 280 μA from an emission spot of 30 μm. For the structured cathodes with a triangular patch array of less dense Cu-NCs (<10⁶ cm⁻²), well-aligned FE with ~90% efficiency is reproducibly achieved. A trade-off between low onset field (~22 V/μm) for sparsely grown Cu-NCs with sharp tips and high current limit (~100 μA) for densely grown ones with broader tips is observed. Possibilities for further optimization of such field emitters for cold cathode applications are discussed.