Paper detail

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

In field electron emission (FE) studies, to interpret current-voltage data and extract characterization parameters, we use smooth planar metal-like emitter (SPME) methodology and a data-analysis plot. Three types exist: Millikan-Lauritsen (ML), Fowler-Nordheim (FN) and Murphy-Good (MG) plots. In SPME methodology, ML and FN plots are slightly curved but a MG plot is nearly straight. 1956 MG FE theory is better physics than 1928 FN theory, so we expect MG plots to be more precise than ML or FN plots. Current-voltage data are often converted: measured voltage to (apparent) macroscopic field, current to macroscopic current density. Thus, four different data-input forms exist. Over-simplified models of system behaviour are widely assumed. Whether simple use of a data-analysis plot is a valid interpretation method is often neglected. Published FE studies seem to contain a high incidence of spurious values for "field enhancement factor". A procedure (the "Orthodoxy Test") described in 2013 allows a validity check: around 40 % of a small sample of results were spuriously high. To assist data interpretation and validity checks, a simple user-friendly webtool has been designed by the lead author. As inputs, this needs system specification data and "range-limits" data from any of the three plot forms, using any of the four data-input forms. The webtool then applies the Orthodoxy Test, and -- if passed -- extracts characterization parameters. This study reports: (1) systematic tests of webtool functionality, using simulated input data prepared using Extended MG FE theory; and (2) systematic comparisons of the three different data-plot types, to check how well extracted parameter values match simulation input values. A summary review of relevant theory is given. For formal emission areas, the MG plot performs better than FN and ML plots. This is important for FE science.