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Monochromatic photocathodes from graphene-stabilized diamondoids Hao Yan, Karthik Narasimha, Jonathan Denlinger, Fei Hua Li, Sung-Kwan Mo, J. Nathan Hohman, Jeremy E. P. Dahl, Robert M. K. Carlson, Boryslav A. Tkachenko, Andrey A. Fokin, Peter R. Schreiner, Zahid Hussain, Zhi-Xun Shen, and Nicholas A Melosh Nano Lett., Just Accepted Manuscript • DOI: 10.1021/acs.nanolett.7b04645 • Publication Date (Web): 29 Dec 2017 Downloaded from http://pubs.acs.org on December 29, 2017
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Nano Letters
Monochromatic photocathodes from graphenestabilized diamondoids Hao Yan1,2†, Karthik T. Narasimha1,2†, Jonathan Denlinger3†, Fei Hua Li1,2, Sung-Kwan Mo3, J. Nathan Hohman3, Jeremy E. P. Dahl2, Robert M. K. Carlson2, Boryslav A. Tkachenko4, Andrey A. Fokin4, Peter R. Schreiner4, Zahid Hussain3, Zhi-Xun Shen2,5 and Nicholas A. Melosh1,2* 1
Department of Materials Science and Engineering, Stanford University, Stanford, CA 94305,
USA 2
Stanford Institute for Materials and Energy Sciences, Stanford, CA 94305, USA
3
Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
4
Institute of Organic Chemistry, Justus-Liebig University, Giessen, Germany
5
Department of Applied Physics, Stanford University, Stanford, CA 94305, USA
KEYWORDS: diamondoid; graphene; monochromatic; photoemission; negative electron affinity
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ABSTRACT
The monochromatic photoemission from diamondoid monolayers provides a new strategy to create electron sources with low energy dispersion, and enables compact electron guns with high brightness and low beam emittance for aberration-free imaging, lithography and accelerators. However, these potential applications are hindered by degradation of diamondoid monolayers under photon irradiation and electron bombardment. Here we report a graphene-protected diamondoid monolayer photocathode with four-fold enhancement of stability compared to the bare diamondoid counterpart. The single-layer graphene overcoating preserves the monochromaticity of the photoelectrons, showing 12.5 meV full-width-at-half-maximum distribution of kinetic energy. Importantly, the graphene coating effectively suppresses desorption of the diamondoid monolayer, enhancing its thermal stability by at least 100 K. Furthermore, by comparing the decay rate at different photon energies, we identify electron bombardment as the principle decay pathway for diamondoids under graphene protection. This provides a generic approach for stabilizing volatile species on photocathode surfaces, which could greatly improve performance of electron emitters.
Photoemission from monolayer-diamondoid coated metal surfaces is characterized by high degree of monochromaticity, with up to 70% photoelectrons residing in a single peak with
