A Plasmon-Mediated Electron Emission Process.

Light-driven electron emission plays an important role in modern optoelectronic devices. However, such a process usually requires a light field either with a high intensity or a high frequency, which is not favor for its implementations and difficult for its integrations. To solve these issues, we propose to combine plasmonic nanostructures with nano-electron-emitters of low work function. In such a heterostructure, hot-electrons generated by plasmon resonances upon light excitation can be directly injected into the adjacent emitter, which can subsequently be emitted into the vacuum. Electron emission of high efficiency can be obtained with light field of moderate intensities and visible wavelengths, which is a plasmon-mediated electron emission (PMEE) process. We have demonstrated our proposed design using a gold-on-graphene (Au-on-Gr) nanostructure, which can have electron emission with light intensity down to 73 mW·cm-2 . It should be noted that the field electron emission is not involved in such a PMEE process. This proposal is of interest for applications including cold-cathode electron sources, advanced photocathodes, and micro- and nano-electronic devices relying on free electrons.