Growth and field-emission properties of vertically aligned cobalt nanowire arrays

We present the fabrication of vertically aligned cobalt nanowire arrays on planar surfaces as well as preliminary field-emission (FE) experiments using them as cold electron cathodes. These arrays are obtained by electrodeposition into nanoporous templates on Au/Ti/Si substrates at very low temperature (<100 degreesC). After the removal of the template, the arrays consist of statistically positioned vertical free-standing nanowires with high aspect ratios, uniform dimensions, and predetermined densities. The electron field-emission measurements show metallic and reproducible characteristics. Emission is found to be reasonably homogeneous over the whole sample area, and a current density of 1 mA/cm(2) has been obtained. We show that the growth process permits us to predetermine the field amplification factor precisely, which is of primary importance for FE sources, A large variety of FE applications can be envisaged, including FE displays and microwave amplifiers.