STRUCTURAL STUDY OF ALLOY FORMATION AT THE CO-PT(111) INTERFACE

This study examines the structure of the surface alloys that form at t he surface of the system formed by depositing cobalt on the clean Pt(1 11) surface. Using mainly XPD as a structure-sensitive technique, surf ace alloys were observed to form in this system after annealing at tem peratures of about 600 K or higher. When starting with a single atomic layer of cobalt, diffusion leads to a surface phase where Pt atoms oc cupy mainly the topmost layer while cobalt atoms are mainly located in the second layer from the surface. Multi-atomic-layer alloying, with the formation of an epitaxial, random substitutional Pt-Co alloy, is o bserved at higher temperatures.