Work functions of the (001) face of the hexaborides of Ba,La, Ce and Sm

From thermonic and field emission retarding potential methods the following order of increasing work function for RB₆-type single crystals was determined: CeB₆(001) ? LaB₆(001) < BaB₆(001) < SmB₆(001) Auger electron spectroscopy indicated that low work function surfaces correlated with low B/R ratios; however, energy dependence of the electron reflection coefficient maxima suggests that a conduction band edge shift relative to the Fermi level among the various RB₆(001) crystals largely accounts for the work function variation. Mass spectrometric studies showed only atomic species vaporizing from all the RB₆ crystals investigated. Large variations in the vapor phase B/R ratios and vaporization energies for crystals of the same material were believed to be due to small variations in bulk stoichiometry.