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

Abstract

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, Φ due to high energy radiation. The practical aspect of the research was connected to the change of the steel's 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, ΔΦ 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 Φ 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 ΔΦ 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.