J. Phys. Colloques
Volume 50, Numéro C8, Novembre 198936th International Field Emission Symposium
|Page(s)||C8-321 - C8-325|
J. Phys. Colloques 50 (1989) C8-321-C8-325
ATOM-PROBE STUDY OF SURFACE SEGREGATION OF Pt-Rh ALLOYSN. SANO et T. SAKURAI
The Institute for Solid State Physics, The University of Tokyo, 7-22-1, Roppongi, Tokyo 106, Japan
An atom-probe field ion microscope (AP-FIM) has been employed to determine the surface composition and its depth profile of the (100) plane of Pt-20, 40wt.% (32.1, 55.8at.%) Rh alloys. The enrichment of Pt at the top surface layer on annealing at 700 C (1000K) was found, agreeing with previous studies by AES, ISS, and AP-FIM. On annealing below 600 C, however, a reversed surface segregation, Rh enrichment at the first layer, has been observed without any impurity atoms such as S and P. An oscillatory behavior was observed in composition of both Pt and Rh over ten atomic layers. 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.