Carbon nanotubes can act as electron sources1 with very rigid structures2, making them particularly interesting for use as point electron sources in high-resolution electron-beam instruments. Promising results have been reported with respect to some important requirements for such applications: a stable emitted current3,4,5 and a long lifetime6,7. Two parameters of an electron source affect the resolution of these instruments: the energy spread of the emitted electrons and a parameter called the reduced brightness, which depends on the angular current density and the virtual source size. Several authors have measured a low energy spread associated with electron emission3,7,8,9. Here we measure the reduced brightness, and find a value that is more than a factor of ten larger than provided by state-of-the-art electron sources in electron microscopes. In addition, we show that an individual multi-walled carbon nanotube emits most current into a single narrow beam. On the basis of these results, we expect that carbon nanotube electron sources will lead to a significant improvement in the performance of high-resolution electron-beam instruments.
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We thank M. Kaiser for the TEM images, N. J. van Druten and B. Buijsse for discussions, T. van Rooij for help with the vacuum system and R. E. Smalley for providing the carbon nanotube sample. N.d.J. was supported by FEI company. T.H.O. was supported by Nederlandse organisatie voor wetenschappelÿk onderzoek and stichting voor fundamenteel onderzoek der materie.
The authors declare that they have no competing financial interests.
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de Jonge, N., Lamy, Y., Schoots, K. et al. High brightness electron beam from a multi-walled carbon nanotube. Nature 420, 393–395 (2002). https://doi.org/10.1038/nature01233
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