Gate-controlled ZnO nanowires for field-emission device application

Gate-controlled field-emission devices have great promise for a number of applications such as bright electron source or flat display array. The gate-controlled ZnO nanowire (NW) field-emission device was fabricated using lift-off fabrication process to synthesize side-gate control in the present investigation. This device effectively controls the turn-on electron beams and switches the drain current (Id) under a threshold gate voltage (VT) of ∼35V. In the meantime, the current density of the device is ∼1mA∕cm2 that is similar to carbon nanotube (CNT) field-emission level with a potential for the design of field-emission display (FED) devices. Furthermore, when the gate voltage (Vg) is equal to 0V, the turn-on electric field (Eto) for ZnO NWs is ∼0.8V∕μm and the effective-field-enhancement factor β is ∼7000. As Vg is increased to 10, 20, 30, and 40V, the Eto lowers to the range of∼0.8–0.6V∕μm and the β value increases to ∼7600–17800. The continuous increases in Vg lowers the turn-on electric field because the local electric field (Elocal) generated induces an extra force that enhances electron emission from the ZnO NWs. Besides, the transconductance (gm) value can approach 0.388mS while the Vg is increased to 44.5V. The devices have well-controlled behavior and exhibit better Fowler-Nordheim characteristic in comparison with classic CNT field-emission devices. The gated ZnO NW array has a good opportunity to be applied to FED devices and be integrated to the semiconductor industry in the future.