Use of HfC(310) as a High Brightness Electron Sources for Advanced Imaging Applications

This paper continues our work to demonstrate a new electron source for applications where high brightness is required. Thermionic emission and cold field emission are ends in a continuum of electron emission processes; between lays extended Schottky emission (ESE) and thermal-field emission (TFE). Presently, commercial electron sources operate in the extended Schottky or cold field emission (CFE) modes both using tungsten as the base material. It is known that surface tension and field forces contribute to blunting or build-up on these W based emitters. However, HfC sources have activation energy for surface migration much large than for W. This coupled with loosely bound surface contaminants mean operation at elevated temperatures can keep the surface clean but not trigger geometric changes.