Independent tuning of work function and field enhancement factor in hybrid lanthanum hexaboride-graphene-silicon field emitters

The authors report the experimental demonstration of independent control over work function and field enhancement factor in hybrid field emitters using a lanthanum hexaboride (LaB6) nanoparticle low-work function coating on monolayer graphene on microfabricated silicon arrays. A critical challenge in field emitters is combining the scalability and uniformity of silicon microfabrication with low-work function materials. Specifically, the authors engineer the field enhancement through microfabrication of the underlying silicon wafers and control the work function by the transfer and deposition of monolayer graphene and LaB6 nanoparticles. Using this coating, the turn-on electric field, defined as the electric field required for 10 mu A/cm(2) of emission current density, drops by 5x from 12.5 to 2.6 V/mu m. To further analyze these results, the authors carried out detailed electronic and structural characterization of the hybrid emitters to experimentally determine the work function and model the field enhancement factor of the physical structure. Using these coupled simulations and experiments, the authors show that the work function and field enhancement factor can be independently controlled, potentially enabling ultralow turn on, uniform, and stable emitters. Published by the AVS.