following the behavior of the Fowler–Nordheim (F–N) equation. The field emission starts around 2.0 V/μm and the maximum current is 4.0 × 10−6A. Figure 4b shows the F–N curve obtained from the I-E curve of the ITO-coated VANA. This curve shows a linear relationship after turn-on electric field intensity, following the F–N equation, as indicated by the red line. The turn-on electric field intensity is 2.0/μm, which can be estimated where the slope of the F–N curve changes. Figure 4c shows the field emission current stability of the ITO-coated VANA over a period of 3 min, measured under a vacuum of 1.59 × 10−5 torr when the electric field intensity (E) is 2.5 V/μm.
Figure 4. a Field emission I-E curve of the ITO-coated VANA measured under a vacuum of 1.59 × 10−5 torr. b Corresponding F–N curve obtained from I-E curve. c Field emission current stability of ITO-coated VANA at 1.59 × 10−5 torr
where I, E, β, φ, A, ℏ, and m are the current, electric field intensity, field enhancement factor, work function, area, reduced Planck constant, and electron mass, respectively. This equation explains the shape of the I-E curve in Fig. 4a and can be modified as follows,
Note that −21.18 is the slope of the red line and −5.76 is the y-intercept of the red line in Fig. 4b. The estimated field enhancement factor of the ITO-coated VANA, β, is 3,078 when the work function of ITO is 4.5 eV . The measured value of the field enhancement factor is comparable with previous research results of field emitters [4,14,15].
In summary, an ITO-coated VANA was fabricated by a top–down method using modified conventional UV lithography, and the field emission characteristics were evaluated using a Zyvex nanomanipulator. The top–down method offers many advantages including an economical process, good fabrication reliability, and suitability for mass production. The turn-on electric field intensity of the ITO-coated VANA is about 2.0 V/μm, and the estimated field enhancement factor β is 3,078. These results show that the ITO-coated VANA is a very promising candidate for vacuum electron field emission applications.
This work was partly supported by Brain Korea 21 and Award No KUK-F1-038-02, made by King Abdullah University of Science and Technology (KAUST).
This article is distributed under the terms of the Creative Commons Attribution Noncommercial License which permits any noncommercial use, distribution, and reproduction in any medium, provided the original author(s) and source are credited.
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