THERMAL FIELD-EMISSION OBSERVATION OF SINGLE-CRYSTAL LAB6

TFE (thermal field emission) properties of LaB6 〈100〉 and 〈310〉 single crystals were investigated by emission pattern observation. It was found that field evaporation with the tip temperature held at ∼1500 °C is very useful to get a clean pattern of fourfold symmetry. Each of four bright spots in the clean pattern was presumed to correspond to 〈310〉 emission. It is proposed, as the most appropriate operating condition, to use the 〈310〉LaB6 tip at a temperature ∼1000 °C in vacuum of 10-9 Torr region, promising a new TF emitter of high brightness and stability for practical use.