Efficient field emission from structured gold nanowire cathodes

Abstract

Regular patch arrays of random gold nanostructures were fabricated by electrochemical deposition of nanowires in ion track-etched templates. During ion irradiation with GeV ions of fluence 10 6 , 10 7 , or 10 8 cm −2 , a shadow mask was used resulting in templates structured with square arrays of 50 μ m holes and 100 or 150 μ m pitch. The Au nanowires grown in the track-etched pores had a length of 7–28 μ m and a diameter of ~300 nm, and were either solitary or clustered after template dissolution. The structured wire ensembles were systematically investigated with scanning electron and field emission scanning microscopy. Field emission with about 90% efficiency was achieved for wide-spaced patch arrays with medium and high number of Au nanowires at 1500 V for 20 μ m anode distance. The current carrying capability of the patches strongly varied between 40 nA and 90 μ A. The corresponding processing effects are correlated to adsorbates and nanostructural changes of the wires which give suitable hints for the optimization of structured Au nanowire cathodes.