Graphene-based micro-emitters and vacuum transistors

The scaling down of thermionic emitters to the microscale is achieved by using microfabrication technologies and graphene working as the emitter. A graphene micro-emitters can be turned on by a voltage of several volts and its emission current exhibits a tunability of up to six orders by a modest gate. Importantly, emission performances of graphene micro-emitters are controllable and repeatable through engineering graphene dimensions by microfabrication technologies. Based on a graphene micro-emitter, a vacuum transistor with high switching performances is experimentally demonstrated. By integrating two graphene-based vacuum transistors, we achieve an ambipolar transistor with perfectly symmetric transfer characteristics centered at 0 V and an ON/OFF current ratio of 10
³
. The ambipolar vacuum transistor shows the potential in AC applications such as frequency multipliers and rectifiers in extreme environments.