The thermal field emission properties of <100> and <310> single crystals were investigated via emission pattern observations. It was found that field evaporation, with the tip temperature held at ∼1500C, was very useful in obtaining a clean pattern having fourfold symmetry. Each of four bright spots in the clean pattern was presumed to correspond to <310> emission. It was proposed, as the most appropriate operating conditions, to use the <310> tip at ∼1000C under a vacuum of 10-9Torr.

Thermal Field Emission Observation of Single-Crystal LaB6. Nagata, H., Harada, K., Shimizu, R.: Journal of Applied Physics, 1990, 68[7], 3614-8