Abstract Films of platinum, gold, and their alloys were prepared by vapor deposition of the metals—either simultaneously or successively—and subsequent sintering under ultrahigh vacuum. The photoelectric emission of these films was investigated and it was found that equilibrated alloys of compositions within the miscibility gap of the PtAu phase diagram possessed identical work functions. This agrees with the expectation, based on thermodynamic and diffusion data, that the gold-rich alloy should envelop crystallites of the coexisting Pt-rich alloy. The work function of the gold-rich alloy is lower than that of gold or that of platinum. These results are completely analogous to those found previously for the CuNi system. The previously predicted dependence of surface composition on the surrounding gas atmosphere has been experimentally verified. Carbon monoxide causes an enrichment of the platinum in the surface. This process takes several days at room temperature and may be reversed by pumping off the carbon monoxide at elevated temperature.
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