Exploring metal-supported few-layer graphene for photocathode application through Cs/O activation process

Exploring a photocathode with features of visible-light response, high quantum efficiency, long life-span, easy availability and low cost is the desire of electron source applications. Here, we report the photoemission behavior of nickel-supported few-layer graphene through Cs/O activation process. We observe that this Cs/O-activated graphene-based photocathode can possess a cut-off response wavelength of 750 nm, a quantum efficiency over 0.1% at 350 nm, and a 1/e operating lifetime of over 50 h under continuous mW-level laser irradiation at a pressure of 10-7 Pa. Importantly, the photoemission capability after degradation can be completely restored again to its original maximum through the additional Cs deposition process. Moreover, the changes in surface composition and work function characterized by in-situ photoelectron spectroscopy demonstrate the low work function and excellent stability. This metal-supported graphene material with low-workfunction surface provides a route to obtain robust photocathode working from ultraviolet to visible waveband. (c) 2022 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).