Lanthanum hexaboride was investigated with regard to its potential as a low work-function photocathode for high-brightness e-beam applications. Thin films of at room temperature were shown to have quantum efficiencies of 0.2 x 10-3 at 442nm excitation but readily formed an inhibiting oxide. This oxide was easily removed by in situ 500eV Ar + ion sputtering, which restored photo-emission for over 30min at an oxygen partial pressure of 10-9Torr.

Photoemission from Thin-Film Lanthanum Hexaboride. May, P.G., Petkie, R.R., Harper, J.M.E., Yee, D.S.: Applied Physics Letters, 1990, 57[15], 1584-5