SURFACE SEGREGATION OF PT-RH ALLOYS

An atom-probe field ion microscope (APFIM) has been employed to determine the surface composition and depth profiles of the (100) plane of Pt-20, 40 wt. % (32.1, 55.8 at. %) Rh alloys. The enrichment of Pt at the top surface layer on annealing at 700 °C (~1000 K) was observed, agreeing with previous studies by Auger electron spectroscopy, ion scattering spectroscopy, and APFIM. On annealing below 600 °C, however, a reversed surface segregation, Rh enrichment at the first surface, has been observed even without any impurity atoms such as S and P. Upon annealing up to 700 °C in the presence of oxygen, we found no appreciable oxidation of the alloy samples, instead, there appeared chemisorbed oxygen forming an overlayer. © 1990, American Vacuum Society. All rights reserved.