Oscillatory compositional depth profiles in surface segregation of a Pt-Rh alloy

Abstract

Surface segregation of a Pt-Rh alloy is studied with the single-atom chemical analysis capability of the atom-probe field ion microscope. We find the composition of the near-surface layers of the {001} plane to oscillate with the depth of the atomic layers having the top layer enriched with Pt. This oscillatory feature persists down to a depth of over ten atomic layers. The amplitudes of the oscillations decrease with the annealing temperature. In contrast, for Pt-Rh alloys containing a small amount of sulfur, the top alloy layer is enriched with Rh but a similar oscillation exists.