The effect of ion irradiation on the electron work function of stainless steel

Stainless steel samples AISI 321 were iradiated with 100 keV H+ and 30 keV Ar+ ions in order to reveal the eventual variation of electron work function, due to high energy radiation. The practical aspect of the research was connected to the change of the steers corrosion resistance in a nuclear reactor. Work function was measured by the Ambient Kelvin Probe method. Irradiation by Ar+ was found to bring about a decrease whereas that by H+ an increase in the work function. To our knowledge these are the first attempts to reveal the effect of ion irradiation on metal work function. The change, Delta Phi exhibited extrema as a function of displacement per atom (DPA) in both cases. The observations were interpreted in terms of the Lang-Kohn theory which describes Phi as a difference between a surface and a bulk potential. The two types of radiation influence the metal density in the same sense and extent but Ar+ ions affect mainly the near-surface region whereas H+ ions act in the bulk. The opposing signs of the contributions from the two regions account for the opposing effects. Since Delta Phi is a linear function of the variation of the electrode potential, irradiation by Ar+ weakens whereas that by H+ strengthens the alloy's corrosion stability, as far as thermodynamics is concerned