The correlation of changes of work-function with changes of phase of the erbium-hydrogen system

The effects of hydrogen on the work-function of erbium films at 295K have been correlated with the various phases of hydrogen-erbium system. The erbium films were evaporated from high-purity metal on to glass substrates in UHV. The changes of work-function were studied by following the change of contact potential difference between the film and a gold reference surface. The phase changes of the system were deduced from changes in the electrical resistance of the films. For the alpha phase of the system, small doses of H2 reduced the work-function phi to 0.1 eV below the value phi 0 for the clean metal, but larger doses increased it to 0.17 eV above phi 0. Further doses H2 took the system into the mixed phase ( alpha + beta ) in which phi quickly rose to a maximum of 0.53 eV above phi 0 and then remained constant throughout the rest of this phase, and the beta phase.