A novel synthesis method of large-area tungsten oxide nanowires arrays and their field emission properties

A very simple catalyst-free approach to fabricate tungsten oxide nanowire arrays on large area silicon substrate is reported. A set of tungsten wires is used as tungsten source. Silicon substrates are placed on a holder ∼2 mm beneath the wires. The chamber is pumped to 1 × 10^-2 Torr and high purity argon is introduced. The tungsten wires are then heated by passing current through them sequentially. At high temperature, the surface is oxidized by the residual oxygen in the vacuum chamber. As a result, tungsten oxide NW arrays are grown on the silicon substrates. Field emission measurements on these nanowires show turn on field of about 9 MV/m which is defined as the macroscopic field required to produce a current density of 10 μA/cm².