Photoemission from thin-film lanthanum hexaboride

Lanthanum hexaboride (LaB6) is investigated for its potential as a low work-function photocathode for high brightness e-beam applications. Thin films of LaB6 at room temperature are shown to have quantum efficiencies of 0.2×10-3 at 442 nm excitation but readily form an inhibiting oxide. This oxide is easily removed by in situ 500 eV Ar + ion sputtering, which restores photoemission for over 30 min at an oxygen partial pressure of 10-9 Torr.