Atmospheric pressure field electron emission from nanostructures

Atmospheric pressure field emission operation of 2 mum gap diode utilizing crystalline W18O49 nanowires, which were grown on sputter deposited tungsten films by thermal annealing at 700degC in ethene and nitrogen, was demonstrated. Field emission measurements in air follows Fowler-Nordheim electron tunneling theory and showed a low turn-on field of 3.3 V/mum, excellent stability and reproducibility with high emission current density (28 mA/cm2). At high electric fields (> 13 V/mum), current density diverged from Fowler-Nordheim equation and space charge limited conduction was observed. Explosion of emitters was observed similar to breakdown of small contact gaps in vacuum under overloading with high density field emission current. Resistive heating and the Nottingham mechanism may have produced the increased temperature during emission. Viability of pulsed electron emission at atmospheric pressure was demonstrated by applying a 100 Hz square wave voltage to the cathode. Pulsed electron emission with good repetition rate was observed.