Methods for characterization of atomic-scale field emission point-electron-source

TL;DR

This paper introduces an experimental method using FIM-FEM microscopes to accurately determine the apparent emission area of atomic-scale field emission electron sources, validating Murphy and Good theory over simplified Fowler-Nordheim analysis.

Contribution

It presents a novel experimental approach for characterizing FE sources at atomic scale, improving accuracy over traditional simplified analysis methods.

Findings

MG theory yields more accurate emission area estimates than FN-based analysis.

Discrepancy in emission area estimates is reduced to a factor of 7.4 with MG theory.

The method enables deduction of source energy spread, brightness, and efficiency.

Abstract

Field emission (FE) electron sources are made close to atomic-scale to reach the highest spatial resolution as well as stable emission for electron microscopy, electron beam inspection and lithography. At present, no single agreed method exists of using FE current-voltage data to extract the apparent emission area, which is needed for predicting some beam properties. The 1956 theory of Murphy and Good (MG) is better physics than the 1920s theory of Fowler and Nordheim (FN) and colleagues, but many researchers use simplified FN theory to analyse experimental data. The present paper reports an experimental method of finding apparent emission area, based on using field ion and field electron microscopes (FIM-FEM). The discrepancy of emission area between the FIM-FEM method and MG-based analysis is a factor of 7.4, while that with simplified FN-based analysis is about 25, confirming MG theory is better for FE data analysis. The result allows deduction of key indicators, including source energy spread, reduced brightness and emission efficiency. A downloadable program is made available to help analysis. Our work provides a new experimental method of characterizing FE electron sources, especially the atomic-scale cold cathode, for which existing plot-based data-analysis methods are not suitable.