Low temperature thermionic electron source with narrow energy spread

A major challenge in the field of electron microscopy is to reach energy resolution as low as 1 meV, which would improve the performance of currently used technologies and facilitate the development of novel techniques. The main roadblock limiting these developments are the currently available electron sources, which can only achieve resolution of 10 meV, an achievement that is already linked to major stability and maintenance issues. We propose to develop a radically new type of electron source based on thermionic emission near room temperature. While thermionic emission is typically a very high temperature process, we have developed a technique to lower virtually any material’s work function to levels which we propose could enable thermionic emission of electrons near room temperature. Besides the lower complexity of a room temperature emitter, lowering the temperature also results in a much narrower kinetic energy distribution compared to cold field emitters. This new type of electron source will allow microscopes to surpass current resolution limits will accelerate and enable the development of new microscopy techniques. During Phase I of this project, we confirmed that the applied mechanism and materials can achieve work functions low enough for thermionic emission close to room temperature and, in fact, what believe to be the lowest work function that has ever been measured. In Phase II of the proposed project, we will (1) extend work functions measurements to identify material combinations to achieve ultra-low work functions, (2) quantify the energy distributions from thermionic electron emission close to room temperature, and (3) assemble a contained electron source prototype. The expected energy resolutions could transform the field of electron microscopy and not only improve existing technologies, but also facilitate the development of new techniques, such as multi-dimensional atomic scale microscopes, enhanced characterization of quantum materials, and high-speed dynamic electron microscopy methods. These novel techniques are likely to be used not only at research institutions but could also quickly find their way into industrial applications, e.g. in the semiconductor and bioscience sectors.