AVS 47th International Symposium
    Surface Science Wednesday Sessions
       Session SS3-WeA

Paper SS3-WeA9
Oxygen Induced Faceting of Ir(210)

Wednesday, October 4, 2000, 4:40 pm, Room 210

Session: Surface and Interface Structure I
Presenter: I. Ermanoski, Rutgers, The State University of New Jersey
Authors: I. Ermanoski, Rutgers, The State University of New Jersey
K. Pelhos, Rutgers, The State University of New Jersey
T.E. Madey, Rutgers, The State University of New Jersey
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As a part of a larger program to study the morphological stability of adsorbate covered metallic surfaces, we have investigated the adsorption of oxygen on fcc Ir(210) and the oxygen induced faceting of Ir(210). The techniques we used include low energy electron diffraction (LEED), temperature programmed desorption (TPD), Auger electron spectroscopy (AES) and scanning tunneling microscopy (STM). The atomically rough Ir(210) surface, when exposed to more than ~0.9L of oxygen and annealed to temperatures higher than 600K, experiences significant morphological restructuring: pyramid-like structures (facets) are formed on the initially planar surface. Our high temperature LEED measurements show that these pyramidal facets exhibit a quasi-reversible behavior upon annealing to higher temperatures. The surface reverts to its planar state at temperatures above 850K but, provided the maximum annealing temperature is below the desorption temperature of oxygen, facets reappear upon cooling to temperatures below 800K. LEED measurements show that these facets have a different structure than the original ones. Furthermore, we are able to remove the oxygen from the surface via catalytic oxidation of CO at 480K, while preserving the faceted structure. TPD and AES have shown that residual adsorbed oxygen and CO are negligible after this procedure. The faceted clean surface is stable up to 600K, but irreversibly reverts to the planar state when annealed above 600K. These experiments indicate that the clean, faceted, metastable Ir(210) surface provides an ideal substrate to study thermal relaxation of nanometer-scale surface features.