Measuring nanoscale local emission characteristics of LAFEs

Applications such as X-ray devices, free-electron lasers, and medical equipment require stable sources of free electrons with high emission currents. Large area field emitters (LAFEs), which have a large number or high density of emission sites, demonstrate the potential to provide electrons with increased current levels at low threshold voltages as desired.

To better understand the formation and stability of macroscopic emission currents from LAFEs, researchers sought to better understand the individual emission sites. Popov et al. developed a method based on multichannel registration and online field emission data processing to determine the local emission characteristics of nanoscale emission sites on LAFEs.

The authors used their method to measure the microscopic current-voltage characteristics of individual emission sites, as well as macroscopic current-voltage characteristics, of several types of LAFEs based on carbon nanotubes and graphene. They are the first to acquire local emission characteristics for a graphene-based emitter, which previous research methods could not estimate.

Using the obtained microscopic current-voltage characteristics, the authors were able to determine emission values, including the field enhancement factor and emission area, which agreed with the predicted values.

“The results of our work show that a complex approach to the study allows a better understanding of the LAFE operation and explains the effects accompanying field emission,” said author Sergey Filippov.

Next, the authors plan to further develop their method to help create and optimize new types of LAFEs.

Source: “Comparison of macroscopic and microscopic emission characteristics of large area field emitters based on carbon nanotubes and graphene,” by Eugeni O. Popov, Anatoly G. Kolosko, Sergey V. Filippov, Evgeny I. Terukov, Roman M. Ryazanov, and Evgeny P. Kitsyuk, JVST: B (2020). The article can be accessed at https://doi.org/10.1116/6.0000072 .