Tunable graphene micro-emitters with fast temporal response and controllable electron emission.

Gongtao Wu,Song Gao,Qing Chen,Lianmao Peng,Xianlong Wei

doi:10.1038/ncomms11513

Abstract

Microfabricated electron emitters have been studied for half a century for their promising applications in vacuum electronics. However, tunable microfabricated electron emitters with fast temporal response and controllable electron emission still proves challenging. Here, we report the scaling down of thermionic emitters to the microscale using microfabrication technologies and a Joule-heated microscale graphene film as the filament. The emission current of the graphene micro-emitters exhibits a tunability of up to six orders by a modest gate voltage. A turn-on/off time of less than 1 μs is demonstrated for the graphene micro-emitters, indicating a switching speed about five orders of magnitude faster than their bulky counterparts. Importantly, emission performances of graphene micro-emitters are controllable and reproducible through engineering graphene dimensions by microfabrication technologies, which enables us to fabricate graphene micro-emitter arrays with uniform emission performances. Graphene micro-emitters offer an opportunity of realizing large-scale addressable micro-emitter arrays for vacuum electronics applications.

Highlights

Microfabricated electron emitters have been studied for half a century for their promising applications in vacuum electronics
graphene micro-emitters (GMEs) possess several advantages in fabrication and performances when compared with traditional thermionic electron emitters
In addition to the great increase of fabrication efficiency, this will make it possible to combine GMEbased vacuum electronic devices and solid-state ones to achieve some new functions by integrating them on the same wafer substrate

Summary

Introduction

Microfabricated electron emitters have been studied for half a century for their promising applications in vacuum electronics. In 1968, Spindt pioneered the fabrication of field electron micro-emitter arrays using microfabrication technologies[1], making it possible to scale down vacuum electronic devices to the microscale In contrast with their bulky thermionic counterparts, field microemitters in an array provide near-instantaneous electron emission and their emission current can be locally tuned by an extraction gate[2]. Regarding the materials for the filaments of microfabricated thermionic emitters, it is highly desired from them to exhibit good electrical conductivity, high decomposition or melting temperature, proper work function and good chemical inertness, as learnt from the properties of the filaments of bulky thermionic emitters They have to be compatible with traditional microfabrication technologies and can be controllably tailored into microscale dimensions by microfabrication technologies. The largemagnitude tunability by a modest gate voltage, fast temporal response and good controllability of emission performances make GMEs promising in realizing large-scale addressable microemitter arrays for vacuum electronics applications

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Conclusion