Alloys and Surface Segregation

Current views on the surface enrichment of one component over another in alloy systems are, surprisingly, more a consequence of gas titration and Auger electron spectroscopy than XPS and UPS. There is little doubt, however, that looking to the future XPS will provide important clues regarding the mechanism of bimetallic catalysts, the significance of promoters. 

The significance of the development of photoelectron spectroscopy over the last decade for a better understanding of solid surfaces, adsorption, surface reactivity, and heterogeneous catalysis has been discussed. The review is illustrative rather than exhaustive, but nevertheless it is clear that during this period XPS and UPS have matured into well-accepted experimental methods capable of providing chemical information at the molecular level down to 10% or less of a monolayer. The information in its most rudimentary state provides a qualitative model of the surface at a more sophisticated level quantitative estimates are possible of the concentration of surface species by making use of escape depth and photoionization cross-section data obtained either empirically or by calculation. 

and Textor, R., Surf. Defect Prop. Solids 5, 189 (1976). 

Fuggle, J. C., in Handbook of X-ray and Ultra-violet Photoelectron Spectroscopy (D. Briggs, ed.), p. 273. Heyden, London, 1977. 

Singh-Boparai, S., Joyner, R. W., and Roberts, M. W. (unpublished results). 

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