AVS 50th International Symposium
    Applied Surface Science Thursday Sessions
       Session AS-ThM

Paper AS-ThM3
Valence-band X-ray Photoelectron Spectroscopic Studies of Phosphorus Oxides and Phosphates

Thursday, November 6, 2003, 9:00 am, Room 324/325

Session: Electron Spectroscopy
Presenter: P.M.A. Sherwood, Kansas State University
Authors: K.J. Gaskell, Kansas State University
M.M. Smith, Kansas State University
P.M.A. Sherwood, Kansas State University
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Valence band X-ray photoemission can be used to identify subtle chemical differences in surface chemistry. Phosphorus oxides are known in a number of different crystalline forms, and a very large number of phosphates are known some of which contain one phosphorus atom, and others contain condensed phosphates with a number of phosphorus atoms in chains, rings and three dimensional structures. The phosphorus oxides can be distinguished from the many phosphate species by valence band X-ray photoelectron spectroscopy (XPS), which is also able to distinguish between different crystalline forms of the oxides. The paper will give an overview of the phosphorus/oxygen valence band spectra, with the spectra interpreted by spectra predicted by band structure and cluster calculations. The paper will also describe how oxide free thin (less than 100@Ao@) films of phosphate species can be formed on metal surfaces, with the phosphate composition altered by changing the pH of the solution used to generate the films, and by changing the type of phosphorus acid used . The work provides an example of how valence band XPS can be especially valuable in the characterization of surface films when it is important to identify small chemical differences. This material was based upon work supported by the National Science Foundation under Grant No. CHE-0137502.