Electron optical characterization of a graphene coated nickel electron source

Highlights: • Noise characteristics and lifetime measurements of a graphene-coated point-cathode emitter under the upper High Vacuum range are presented. • The energy spread broadening at high emission current density due to mutual coulomb repulsion between the electron-electron interactions was studied. • These results provide data from which low energy beam applications can be developed for the cold field graphene coated nickel electron source. - Abstract: Graphene coated nickel electron sources have been recently reported to have significant advantages over state-of-the-art conventional tungsten cold field emission sources for electron microscopy/lithography applications. In this article, noise characteristics and lifetime measurements of a graphene-coated point-cathode emitter are presented in a vacuum chamber with a base pressure of 2×10⁻⁹ Torr. The results show that the emitter is able to operate at a high current density (1 μA/sr) for 600 h without decay. The energy spread broadening at high emission current density due to mutual coulomb repulsion between the electron-electron interactions (the Boersch effect) was experimentally estimated, and found to increase with greater extraction voltages and decreasing tip sizes. These results provide data from which low energy beam applications can be developed for the cold field graphene coated nickel electron source.