Engineering the field enhancement factor and work function toward ultra-low threshold field electron emitter

This paper presents the experimental demonstration of control over field enhancement factor and work function of the hybrid field emitter to reduce the threshold field required for electron emission. The field enhancement is engineered through microfabrication of the underlying silicon wafers, and the work function is controlled by the transfer and deposition of monolayer graphene and low work function lanthanum hexaboride (LaB
₆
) nanoparticles. As a result, the threshold field, defined as the electric field required for 10 μA/cm
²
of emission current density achieved as small as 2.6 V/μm. We also carry out photoemission spectroscopy (PES) to measure the effective work function of our emitters as 3.62eV, significantly lower than work function of the graphene. The measured work function allows us independent extraction of the field enhancement factor of underlying silicon tip array from Fowler-Nordheim (FN) analysis of the experimental I-E curves. Through these measurements and work function characterization, we show that the work function and field enhancement factor can be independently controlled, potentially enabling ultra-low turn on, uniform, and stable emitters.