Nanoscale structuring of tungsten tip yields most coherent electron point-source

TL;DR

This paper reports the creation of a highly coherent tungsten electron source with a record coherence angle, achieved through nanoscale structuring and precise etching, enabling advanced electron microscopy applications.

Contribution

It introduces a novel nanoscale fabrication method for tungsten tips that significantly enhances electron source coherence and brightness.

Findings

Achieved a coherence angle of 14.3 degrees.

Measured a virtual source size of 1.7 Angstrom.

Brightness normalized to 7.9x10^8 A/sr cm^2.

Abstract

This report demonstrates the most spatially-coherent electron source ever reported. A coherence angle of 14.3 +/- 0.5 degrees was measured, indicating a virtual source size of 1.7 +/-0.6 Angstrom using an extraction voltage of 89.5 V. The nanotips under study were crafted using a spatially-confined, field-assisted nitrogen etch which removes material from the periphery of the tip apex resulting in a sharp, tungsten-nitride stabilized, high-aspect ratio source. The coherence properties are deduced from holographic measurements in a low-energy electron point source microscope with a carbon nanotube bundle as sample. Using the virtual source size and emission current the brightness normalized to 100 kV is found to be 7.9x10^8 A/sr cm^2.