Field emission: Why converting LAFE voltages to macroscopic fields before making a Fowler-Nordheim plot has often led to spurious characterization results

TL;DR

This paper highlights that converting voltages to macroscopic fields before Fowler-Nordheim analysis often causes false characterization results in large-area field emitters, advocating for raw data use and orthodoxy testing.

Contribution

It identifies the defective pre-conversion equation as the cause of spurious FEF values and recommends analyzing raw data with orthodoxy tests for more reliable characterization.

Findings

Approximately 40% of published FN plots had spuriously high FEF values.

Pre-conversion equations may be incompatible with circuit theory for non-ideal devices.

Using raw data and orthodoxy tests improves the reliability of LAFE characterization.

Abstract

An important parameter used to characterize large-area field electron emitters (LAFEs) is the characteristic apex field enhancement factor {\gamma}_C. This parameter is normally extracted from the slope of a Fowler-Nordheim (FN) plot. Several years ago, the development of an "orthodoxy test" allowed a sample of 19 published FN plots relating to LAFEs to be tested, and it was found that about 40% of the related papers were reporting spuriously high values for {\gamma}_C. In technological papers relating to LAFE characterization, common practice is to pre-convert the measured voltage into an (apparent) value of macroscopic field before making and analyzing a FN plot. This paper suggests that the cause of the "spurious-FEF-value" problem is the widespread use of a pre-conversion equation that is defective (for example, not compatible with ordinary electrical circuit theory) when it is applied to so-called "non-ideal" field emission devices/systems. Many real devices/ systems are non-ideal. The author argues that FN plots should be made using raw experimental current-voltage data, and that an orthodoxy test should be applied to the resulting FN plot before any more-detailed analysis, and that (in view of growing concerns over the reliability of published "scientific" results) reviewers should scrutinize field emission materials-characterization papers with enhanced care.