Scanning Microscopy


The modification of the chemisorption properties of single crystal metal surfaces by thin film overlayers of a second metal has been a subject of intense investigation. In this paper, selected work from our laboratory is reviewed with particular attention being paid to the different roles played by the added metal. In the case of Ag (111), the chemisorption of CO is enhanced by added potassium even when the potassium is not detectable by AES. We propose that subsurface potassium is effective in altering the surface properties of Ag so that relatively strong CO-Ag bonding occurs. In the case of ketene on copper-covered Ru (001), new bonding modes for molecular ketene and different decomposition product distributions are found for sub-monolayer amounts of added Cu. For Cu coverages greater than one monolayer, there is no decomposition of ketene. For Ag on Rh (100), the chemisorption of oxygen and nitrous oxide follows a simple site blocking model.

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