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

TL;DR

This paper introduces a user-friendly webtool for interpreting field emission current-voltage data, validating its effectiveness through systematic testing and comparison of different data-plot types based on extended Fowler-Nordheim theory.

Contribution

A new webtool for FE data analysis that incorporates the Orthodoxy Test and systematically compares plot types for improved parameter extraction.

Findings

MG plots yield more accurate emission parameters than FN and ML plots.

The webtool successfully validates data and extracts parameters using simulated data.

Extended FE theory enhances the understanding and interpretation of emission data.

Abstract

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.