Field Emission Properties of Metallic Nanowires Grown in Polymer Ion-track Membranes

The field emission (FE) properties of randomly distributed free-standing Cu and Ni nanowires on thin metallic substrates were measured. The wires were grown in the etched ion-tracked pores of polycarbonate membranes with various diameters of 120-330 nm, lengths of 8-18 mum and number densities of 10⁶-10⁸ emitters/cm². The emission site density and current distribution of the nanowire cathodes were measured with the field emission scanning microscope (FESM) at about 10^-7 Pa. All samples showed similar onset fields for 1 nA of some V/mum but rather different emission uniformity. At 5 V/mum the free standing Cu and Ni nanowires provided less than 4times10⁴ emitters/cm² , while the bundled Cu and Au-coated Ni nanowires yielded more than 10⁵ emitters/cm². For the latter sample about 1.6times10⁶ emitters/cm² were found at 18 V/mum, i.e. about than 10 % of the nanowires emitted