Introduction:
The NIST X-ray Photoelectron Spectroscopy (XPS) Database gives easy access to the energies of many photoelectron and Auger-electron spectral lines. Resulting from a critical evaluation of the published literature, the database contains over 22,000 line positions, chemical shifts, doublet splittings, and energy separations of photoelectron and Auger-electron lines. A highly interactive program allows the user to search by element, line type, line energy, and many other variables. Users can easily identify unknown measured lines by matching to previous
measurements. Version 3.1 of the database has an expanded capability for displaying Wagner plots. These plots can now be prepared for 42 elements. In addition, mistakes have been corrected in some data records. Version 3.2 has two new search and display options: Retrieve Auger Parameter data for selected elements and Retrieve Doublet Separation data for selected elements. Version 3.3 contains 3,000 additional data records. The screen on which Wagner plots are displayed has been redesigned to show median energies (for materials for which two or more binding energies or Auger kinetic energies are available) rather than to indicate the midpoints of the ranges as was done previously. Wagner plots are now available for 50 elements. Version 3.4 has a new search and display option: Retrieve Data for a Selected Element. The following main search and display options are available: Newly added data (since the release of version 2.0) contain considerable additional information about the specimen materials, the XPS measurement conditions, and the methods used to analyze the XPS measurements. There may also be comments about the specimen morphology and the specimen treatments. This information can be used to assess the significance of the reported data. Finally, data have been included on surface core-level shifts. Interested scientists can use the last search option to check whether data from selected sources were included in the database. Although computer searches were made of the scientific literature (using searches of key words such as XPS, X-ray photoelectron spectroscopy, X-ray photoemission, surface core-level shift, ESCA, and electron spectroscopy for chemical analysis in the title, abstract or key words of published papers), it is possible that papers with useful data may have been missed. In such cases, NIST would appreciate being informed (by email to cedric.powell@nist.gov or john.rumble@nist.gov) of the relevant citations. Version 3.0 of the database contains data from papers published through 1992. Additional data from later papers will be added to the database on a continuing basis as soon as possible. Help screens are available to guide the user, and descriptions are available of the various data fields. Versions 2.0 and 3.0 of the database contain data that have been standardized to a binding-energy scale for which the following lines and energies were used as calibrants: Au 4f7/2 = 84.00 eV, Ag 3d5/2 = 368.27 eV, Cu 2p3/2 = 932.67 eV, and C 1s (for hydrocarbon or hydrocarbon groups) = 284. 8 eV. Work at the UK National Physical Laboratory [M. P. Seah, I. S. Gilmore, and G. Beamson, Surf. Interface Anal. 26, 642 (1998)] has led to small revisions of the calibration energies for the three noble metals. The positions of these peaks vary slightly on the binding-energy scale depending on the X-ray source due to differences in X-ray spectral lineshapes. The reported calibration energies vary for the Au 4f7/2 line between 83.95 eV and 83.96 eV, for the Ag 3d5/2 line between 368.21 and 368.22 eV, and for the Cu 2p3/2 line between 932.62 eV and 932.63 eV for a monochromatized aluminum Ka X-ray source, an unmonochromatized Mg Ka X-ray source, and an unmonochromatized Al Ka X-ray source. Since the changes in the calibration energies for the three metals, approximately 0.05 eV, are small for most practical applications, it was decided not to make revisions at the present time to previous and newly added binding energies in the database to take account of the new calibration energies. Data have been included in the XPS database from papers in which specimen materials were in a well-defined physical and chemical state and in which at least one measurement was reported of the position of a calibration line on the instrumental binding-energy scale. If any such measurement differed from the reference values, corrections were made to the reported energies as described in the help screen for Quality of Data.