Introduction to Studies of Phosphorus-Oxygen Compounds by XPS

Phosphorus is an essential element, and phosphorus oxygen compounds (normally in the form of phosphates) are an essential component in the growth of animals and plants. Most phosphates are insoluble in water, and exist in the form of solids such as vegetable and animal tissues, seeds, bones, soils, fossils, and mineral deposits. Phosphates have many important applications as fertilizers, corrosion inhibitors, and adhesion promoters. The XPS spectra of phosphates show similar P 2p spectra, but significant differences in the O 1s region as a result of the different oxygen environments possible in different forms of phosphates. The valence band region is especially valuable in the case of phosphates because the P 2s and P 2p atomic orbitals interact with O 2s and O 2p atomic orbitals to give molecular orbitals in the outer valence band region (at binding energies less than 20 eV) to give a spectrum that is often very characteristic of a particular type of phosphate. This introduction provides a summary of the data to be presented and provides an overview of the interpretation of the data in the core and valence band regions.