Abstract
In this study, we propose to coat metal nano-emitters with an atomically thick dielectric to further enhance the laser field near the nanotips and therefore the photoemission current. An optical field enhancement factor of up to 400 is demonstrated by the full-wave optical simulation, depending on the geometry of the nano-emitter and resonance wavelengths. A quantum photoemission model, which is constructed by solving the time-dependent Schrödinger equation, is utilized to investigate the photoemission processes. It is found that, over a wide range of laser fields, the emission current density from the coated photoemitter is enhanced by at least 2 orders of magnitude as compared to the bare emitter. The optical field emission regime can be reached at a much smaller field strength compared to the bare emitter.