Stable field emission from arrays of vertically aligned free-standing metallic nanowires

Abstract

We present a fully elaborated process to grow arrays of metallic nanowires with controlledgeometry and density, based on electrochemical filling of nanopores in track-etchedtemplates. Nanowire growth is performed at room temperature, atmospheric pressureand is compatible with low cost fabrication and large surfaces. This techniqueoffers an excellent control of the orientation, shape and nanowires density. It isapplied to fabricate field emission arrays with a good control of the emissionsite density. We have prepared Co, Ni, Cu and Rh nanowires with a height of3 µm, a diameter of 80 nmand a density of ∼107 cm−2. The electron field emission measurements and total energy distributions show that theas-grown nanowires exhibit a complex behaviour, first with emission activation under highfield, followed by unstable emission. A model taking into account the effect of anoxide layer covering the nanowire surface is developed to explain this particularfield emission behaviour. Finally, we present an in situ cleaning procedure by ionbombardment that collectively removes this oxide layer, leading to a stable andreproducible emission behaviour. After treatment, the emission current density is∼1 mA cm−2 fora 30 V µm−1 applied electric field.