The Work Function of Copper

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Abstract
The work functions and aging characteristics of fourteen copper surfaces have been determined by measurement of their contact differences of potential with respect to barium reference surfaces of known work function. Measurement was by the retarding potential method in tubes sealed from the pumps and gettered with vaporized barium. The copper surfaces were prepared by subjecting Hilger's "spectroscopic standard" copper to forty vacuum fusions followed by fractional distillation, redistillation of the fractions, and condensation of the vapor on glass. The barium films were prepared by a similar, standardized technique which yields surfaces reproducible and constant to 0.01 ev or better. The time interval between the deposition and initial measurement of the metal films was of the order of ten seconds, obtained conveniently with a tube in which the target is returned to the measuring position automatically after deposition of a metal film upon it.