Low temperature electrical characterisation of tungsten nano-wires fabricated by electron and ion beam induced chemical vapour deposition

In this study we have fabricated tungsten containing nano-wires using focused electron and ion beams from a tungsten hexacarbonyl precursor. The temperature dependent conductive properties of the wires have been investigated. Although a superconducting transition (at ∼ 5.5 K) has been observed in ion beam deposited wires, electron beam deposited wires display non-metallic conduction properties consistent with a variable range hopping conduction mechanism. Micro-structural and compositional analysis has been performed using transmission electron microscopy and associated techniques. The observed disorder of the as-deposited wires, together with the higher oxygen and lower metal content of the electron beam deposited wires was found to correlate well with the low temperature electrical properties. In addition, the electron beam deposited wires were shown to be particularly susceptible to irradiation damage when illuminated using 200 kV electrons in the transmission electron microscope. With electron doses in the region of ∼ 50 A/cm2 the as-deposited disordered structure was refined locally to give regions of randomly orientated nano-crystallites.