ABSTRACT
Carbon is an extremely promising material for cold cathode electron emission. The various carbon allotropes, in particular the graphic sp3 derivatives; the fullerenes and carbon nanotubes (CNTs), have been some of the most widely studied materials in the arena of eld emission. Their low sputter coefcients, rapid temporal responses, low surface defect densities, high stability, and largely hysteresis-free emission proles which require little conditioning, make them excellent candidate materials, whilst their negative variation in resistance with temperature intrinsically ballasts their emission during operation preventing avalanche run-away and consequent emitter burn-out. Nanocarbons support current densities three orders of magnitude greater than copper and their high resistance to electromigration offer thermodynamically stable nanoscopic morphologies, which in the case of graphene and CNTs endows them with exceptionally high aspect ratios which enhance their electron emission performance greatly. In this chapter, we will summarize the recent inux of research on graphene-based eld emission electron sources. Despite a number of impressive recent advances in fabrication it is nevertheless clear that it remains a challenge to fabricate en masse large-area vertically aligned graphene emitters with high uniformity and emission reproducibility. We proceed by considering commercially viable and scalable routes of exploiting the extremely high in-plane eld enhancement of graphene via the development of an in-plane edge emitter geometry which decouples the electric eld of the horizontal graphene from the proximal bulk substrate on which the graphene lies. We conclude by presenting recent work emphasizing the alternative uses of graphene in electron emission devices; namely as an electron transparent gate in vacuum microelectronic triodes.
