Metal surfaces, overlayer structure

A breakdown of the structural results by type of surface shows results for nearly 50 clean, unreconstructed metal surfaces and about 10 alloys and reconstructed metal surfaces. The structures of about 65 atomic overlayers on metal surfaces have been determined, some 40 of these involving chalcogen atoms. Just over 20 molecular structures have been determined for metal surfaces, half of these being overlayers of undissociated carbon monoxide and the others various hydrocarbons. Turning to semiconductors, some 13 clean, usually reconstructed structures were determined, against nearly 10 atomic overlayer structures. In addition, about 15 insulator surface structures have been investigated. 

M. W. Roberts, The nature and reactivity of chemisorbed oxygen and oxide overlayers at metal surfaces as revealed by photoelectron spectroscopy, in Structure and Reactivity of Surfaces, ed. C. Morterra, A. Zechina and G. Costa, Elsevier, Amsterdam, 1989, p. 787. 

Overall reaction, 32 281, 285-287 see also Simple overall reactions Overlayer structure, adsorbates on metal surfaces, 29 7-8... 

Selected Overlayer Structures for Adsorbates on Metal Surfaces... 

Figure 4.13. Calculated shifts in the d band centers for a number of overlayer structures. The shifts are calculated relative to the d band center for the pure overlayer metal surface. The shifts therefore reflect the change in reactivity of the overlayer relative to the pure metal. Adapted from ref. [44].

This combination of techniques allows us to determine the structure of the adsorbed species while on the metal surface and after desorption into the gas phase. Furthermore, molecular rearrangements in the adsorbed overlayer as a function of both the substrate temperature and background pressure can be studied. 

Recent studies of supported vanadium oxide catalysts have revealed that the vanadium oxide component is present as a two-dimensional metal oxide overlayer on oxide supports (1). These surface vanadium oxide species are more selective than bulk, crystalline V2O5 for the partial oxidation of hydrocarbons (2). The molecular structures of the surface vanadium oxide species, however, have not been resolved (1,3,4). A characterization technique that has provided important information and insight into the molecular structures of surface metal oxide species is Raman spectroscopy (2,5). The molecular structures of metal oxides can be determined from Raman spectroscopy through the use of group theory, polarization data, and comparison of the... 

---