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J. Vac. Sci. Technol. B 28, C2A33 (2010); http://dx.doi.org/10.1116/1.3363858 (10 pages)

Comparison of approximations for the principal Schottky–Nordheim barrier function v(f), and comments on Fowler–Nordheim plots

Richard G. Forbes1 and Jonathan H. B. Deane2

1Advanced Technology Institute, Faculty of Engineering and Physical Sciences, University of Surrey, Guildford, Surrey GU2 7XH, United Kingdom
2Department of Mathematics, Faculty of Engineering and Physical Sciences, University of Surrey, Guildford, Surrey GU2 7XH, United Kingdom

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(Published online 31 March 2010)

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The Fowler–Nordheim-type (FN-type) equation developed by Murphy and Good [Phys. Rev. 102, 1464 (1956) ] contains in its exponent a correction function v, best called the “principal Schottky–Nordheim (SN) barrier function.” In the last 50 years a large number of different approximations have been developed for v. This article reformulates these approximations to be functions of the scaled barrier field f rather than the Nordheim parameter y, and then compares them with the approximations v(f) ≈ 1−f+(1/6)f ln f and v(f) ≈ 1−f+0.1715f ln f recently reported. It is confirmed, as expected, that these new formulas outperform older approximations of equivalent complexity when the comparison is made over the range 0 ≤ f ≤ 1. However, particularly with the first formula, some older approximations are superior over limited ranges of f because they have been designed to perform well over these limited ranges. The article also presents an updated and fuller account of the theory of FN-plot analysis and an updated tabulation of values of the SN-barrier functions (also called field emission elliptic functions). Both updates use f (rather than y) as the main auxiliary variable. The limitations of the existing FN-plot theory are clarified; this reinforces the case for the development of higher quality measurements of current-voltage characteristics and of new methods of data analysis that may be able to supersede the use of FN plots.

© 2010 American Vacuum Society

Article Outline

  1. BACKGROUND
  2. FORBES 2006 AND RELATED APPROXIMATIONS
  3. COMPARISON WITH OLDER APPROXIMATIONS
  4. ANALYSIS OF FOWLER–NORDHEIM PLOTS
    1. Introduction and background theory
    2. FN-plot analysis: General
    3. Tangent method
    4. Substitution and linearization methods
    5. Chord method
    6. Commentary
  5. SUMMARY AND DISCUSSION

KEYWORDS and PACS

PACS

  • 79.70.+q

    Field emission, ionization, evaporation, and desorption

  • 73.40.Gk

    Tunneling

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PUBLICATION DATA

ISSN

1071-1023 (print)  
1520-8567 (online)

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