Low voltage field emission of Cu nanowire with nanogap in air

Field emission properties of single Cu emitter with nanometer scale cathode-anode distance are investigated here. Field emission was achieved below 5 volts under atmospheric conditions with 20 nm gap between the cathode and anode. The turn-on voltage is 2 V and the maximum current reaches to 32.5 nA at 5 V. With the help of focus ion beam etching, the cathode-anode distance was precisely controlled from 20 nm to 80 nm to study the influence of cathode-anode distance on field emission properties. The emission current drops exponentially with increasing cathode-anode distance. Due to the short electrode gap, the applied voltage is much lower than that in previous works and the field emission current is large for a single Cu emitter. This work provides a practical way to design and optimize nanoscale field emission devices such as vacuum field emission transistors.