Sharp bare and gold-coated copper nanocones with improved field emission performance

We have optimized the fabrication of sharp copper nanocones (Cu-NCs) for flat patch-structured field emission (FE) cathodes. Polycarbonate (PC) foils were irradiated through a shadow mask with swift Xe or U ions. The ion tracks were asymmetrically etched in a mixture of NaOH and methanol. These membranes were metallized, fixed on an Al plate, and electrochemically filled with Cu through the small pore openings. Flat cathodes of 25 mm² size with mechanically stable Cu-NCs of ~28 μm height, ~3 μm base, and ~130 nm tip diameter were obtained. Fairly distributed FE with at least 8 (10) emitters per patch was achieved for the bare (60-nm Au-coated) Cu-NCs. Integral measurements of selected patches yielded average stable FE currents up to 30 (151) μA at 32 (50) V/μm, respectively.