Challenging the Status Quo in Field Emission Electron Source Research

The field emission source of electrons is an important area of study for a wide array of applications, from the generation of X-rays to devices that detect defects in high-end microchips. Better understanding their properties, after all, will enable the development of improved devices used in such applications.

One common method for examining these electron sources, the Fowler Nordheim (F-N) theory, involves extrapolating an electron current emitted for an infinite voltage to try to extract physical information from the emitter such as its area, radius of curvature, or work function. The approach typically models electron field emitter performance linearly and sometimes shows a correlation between fitted slopes and intercepts.

Yet, the method is unreliable and has inspired other hypotheses to determine correlations, including one that extracts slopes and intercepts and suggests emitter “drift” as a determinative physical phenomenon.

Ayari et al. used a simple model along with meta-analysis to challenge the assumption of a physical correlation altogether.

“Our work has shown the correlation comes from mathematical properties and not from physical properties,” said author Anthony Ayari.

Using a 15-nm tungsten tip, the researchers performed emission experiments in an ultra-high vacuum chamber to show, with the aid of linear regression theory, that the correlation between the slope and the intercept can be deduced from three experimental parameters: the mean current, the mean applied voltage and the current fluctuations.

While it may not shed light on the field emission source of electrons, the study may provide direction for future inquiries.

“Outside our field, this result may be of interest because the F-N extrapolation technique is widely used and the same type of mathematical correlation exists,” said Ayari.

Source: “Is the linear relationship between the slope and intercept observed in field emission S-K plots an artifact?,” by Anthony Ayari, Pascal Vincent, Sorin Perisanu, Philippe Poncharal, and Stephen T. Purcell, Journal of Vacuum Science & Technology B (2024). The article can be accessed at https://doi.org/10.1116/6.0003828 .