A determination of the low work function planes of LaB 6

Abstract

A study of the temperature and orientation dependence of the field ion and electron emission and the average work function for a LaB 6 emitter have been carried out between 77 and 1800 K. These results indicate that the (310) surface is thermally stable and has the lowest work function of any single crystal plane of LaB 6. This result is confirmed by field emission retarding potential (FERP) work function (φ) measurements at 300 K which gives φ (310) = 2.50 eV. The results show that the relative orientation dependence of the room temperature work function is φ (310) < φ (210) < φ (100) < φ (110) < φ (111) < φ (211). This ordering is in accordance with the relative dipole contribution to the work function when surface reconstruction is included. The orientation dependence of the field electron emission is sensitive to field evaporation, thermal equilibration, and carbon contamination.