A high-brightness large-diameter graphene coated point cathode field emission electron source

Xiuyuan Shao,Anjam Khursheed,Avinash Srinivasan,Wei Kean Ang

doi:10.1038/s41467-018-03721-y

Xiuyuan Shao, Anjam Khursheed + Show 2 more

Open Access

https://doi.org/10.1038/s41467-018-03721-y

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Journal: Nature Communications	Publication Date: Mar 29, 2018
Citations: 60	License type: open-access

Affiliation: National University of Singapore

Abstract

There have been several long-standing problems of cold field emission sources for electron microscopy and lithography that have prevented their widespread use, such as their inherent ultrahigh vacuum condition requirement (<10–9 torr), relatively poor current stability and rapid emission decay. This paper presents a cold field emission electron source which overcomes these problems based upon using a graphene-coated nickel point cathode. Preliminary experiments demonstrate that it provides stable emission for relatively large tip diameters (micron sizes), can operate in high vacuum conditions (>10−8 torr) and has an ultralow work function value of 1.10 ± 0.07 eV. It has an estimated reduced brightness value of 1.46 × 109 A m−2 sr−1 V−1 for cathode tip-radius of 170 nm and the measured energy spread ranges from 0.246 eV to 0.420 eV for a tip radii range of 260 nm to 500 nm, which is comparable to state-of-the-art conventional cold field emission sources.

Highlights

There have been several long-standing problems of cold field emission sources for electron microscopy and lithography that have prevented their widespread use, such as their inherent ultrahigh vacuum condition requirement (
A variety of other possible types of cold field emission cathodes have been reported in the past decades, such as a tungsten nanowire[8], a carbon nanotube[2,9,10], a carbon nanotip[4,7] and a LaB6 nanowire[3], their practical difficulties are in general even more severe than for the conventional single crystal sharpened tungsten wire cathode source: the vacuum pressure requirement needs to be typically lower than 10−10 torr for nanowire-based field emitters, otherwise the emission currents will suffer from large fluctuation and rapid emission decay
These were used as catalysts and templates for the growth of few-layer graphene via chemical vapor deposition (CVD) process at a moderate temperature (