11.3: Electron emission from hafnium carbide

HfC was evaluated as a cold field emission source. Single crystal HfC was produced and fabricated into cold field emitters, then angular intensity and reduced brightness were determined from experimental I(V) data. Energy distribution data were in agreement with a theoretical model. The reduced brightness, energy distribution, and emission stability are compared to commercially available sources which show that HfC produced a higher brightness and a lower energy spread than a W cold field source or a ZrO/W Schottky emitter. HfC maintains its emission level for one hour in moderate UHV condition; a dramatic improvement over the stability of W. This combined with a durability that allows for frequent flash cleaning without degradation of the emitter end form make HfC a highly promising source. We compared stability and noise to emission from a tungsten tip at the same angular intensity. By increasing the emitter temperature slightly, stability is improved while maintaining a low energy spread.