Interpretation of field emission current-voltage data: Background theory and detailed simulation testing of a user-friendly webtool

In field electron emission (FE) studies, interpretation of measured current-voltage characteristics and extraction of emitter characterization parameters are usually carried out within the framework of "smooth planar metal-like emitter (SPME) methodology", using a data-analysis plot. This methodology was originally introduced in the 1920s. Three main data-plot types now exist: Millikan-Lauritsen (ML) plots, Fowler-Nordheim (FN) plots, and Murphy-Good (MG) plots. ML plots were commonly used in early FE studies, but most modern analysis uses FN plots. MG plots are a recent introduction. Theoretically, it is now known that ML and FN plots are predicted to be slightly curved in SPME methodology, but a Murphy-Good plot will be very nearly straight. Hence (because 1956 Murphy-Good emission theory is "better physics"than 1928 Fowler-Nordheim emission theory as corrected in 1929), expectation is that parameter extraction using a MG plot will be more precise than extraction using either ML plots or FN plots. In technological FE studies, current-voltage characteristics are often converted into other forms. Thus, measured voltage may be converted to (apparent) macroscopic field, and/or current values may be converted to macroscopic current densities. Thus, four data-input forms can be found in the context of analysing FE current-voltage results. It is also the case that over-simplified models of measurement-system behaviour are very widely assumed, and the question of whether simple use of a data-analysis plot is a valid data-interpretation procedure for the particular system under investigation has often been neglected. Past published studies on field emitter materials development appear to contain a high incidence of spurious values for the emitter characterization parameter "characteristic field enhancement factor". A procedure (the so-called "Orthodoxy Test") was described in 2013 that allows a validity check on measurement-system behaviour, and found that around 40% of a small sample of results tested were spuriously high, but has had limited uptake so far. To assist with FE current-voltage data interpretation and validity checks, a simple user-friendly webtool has been under design by the lead author. The webtool needs as user input some system specification data and some "range-limits"data from any of the three forms of data-analysis plot, using any of the four data -input variations. The webtool then applies the Orthodoxy Test, and-if the Test is passed-calculates values of relevant emitter characterization parameters. The present study reports the following: (1) systematic tests of the webtool functionality, using simulated input data prepared using Extended Murphy-Good field electron emission theory; and (2) systematic compar-isons of the three different data-plot types, again using simulated input data, in respect of the accuracy with which extracted characterization parameter values match the simulation input values. The paper is introduced by a thorough summary review of the theory on which modern SPME-based current-voltage data-analysis