Kinetic electron emission from Al, Cu, and Au surfaces exposed to oxygen

Kinetic electron emission is studied for the impact of 3-keV electrons and of 4-MeV He2+ ions on polycrystalline Al, Cu, and Au targets, as a function of oxygen exposure. For electron-induced emission,the yield and the change of the work function is measured, whereas for ions the distribution of the number of emitted electrons is measured. The distributions found are very well fitted by Polya distributions, giving the ion-induced emission yield and the Polya parameter b. For Au targets, no influence of oxygen exposure upon electron emission was found. For Al targets, exposure up to 50 L gives a reduction of the emission yield; further exposure results in oxidation of aluminum and increases the yield. The work function is found to decrease with increasing oxygen exposure. The parameters b of the Polya distributions are almost independent of oxygen exposure. For Cu targets; oxygen exposure gives a decreasing emission yield, and a slightly increasing work function. The results are discussed in terms of existing models of oxygen adsorption. [S1050-2947(97)07510-0].