Applying the Field Emission Orthodoxy Test to Murphy-Good Plots

Abstract

In field electron emission (FE) studies, it is important to check and analyze the
quality and validity of results experimentally obtained from samples, using suitably plotted
current-voltage [Im(Vm)] measurements. For the traditional plotting method, the FowlerNordheim (FN) plot, there exists a so-called "orthodoxy test" that can be applied to the FN
plot, in order to check whether or not the FE device/system generating the results is "ideal".
If it is not ideal, then emitter characterization parameters deduced from the FN plot are
likely to be spurious. A new form of FE Im(Vm) data plot, the so-called "Murphy-Good
(MG) plot", has recently been introduced (R.G. Forbes, Roy. Soc. Open Sci. 6 (2019)
190912). This aims to improve the precision with which characterization-parameter values
(particularly values of formal emission area) can be extracted from FE Im(Vm) data. The
present paper compares this new plotting form with the older FN and Millikan-Lauritsen
(ML) forms and makes an independent assessment of the consistency with which slope
(and hence scaled-field) estimates can be extracted from an MG plot. It is shown that, by
using a revised formula for the extraction of scaled-field values, the existing orthodoxy test
can be applied to Murphy-Good plots. The development is reported of a prototype web tool
that can apply the orthodoxy test to all three forms of FE data plot (ML, MG and FN).

Keywords: Field emission, Field electron emission, Murphy-Good plot, Fowler-Nordheim
plot, Millikan-Lauritsen plot, Orthodoxy test.