The AES work undertaken in Project 193 allows analysts working in the direct mode to agree on absolute peak intensities to within + 3%. However, for the differential mode this agreement degrades to worse than + 10 % even when operating under reference conditions. Since many instruments are only capable of working in the differential mode, it is necessary to improve the traceability of the intensity scale in this mode and to establish procedures which relate the scale established under reference conditions to those under other operating conditions. This the project is attempting to do via the production of a reference material which will allow traceability to an absolute AES intensity scale which is comprised of peaks throughout the spectrum which correspond to known intensities irrespective of the operating conditions.
The development of a fully instrumented electron spectrometer to measure absolute spectral intensities for AES and XPS significantly changed the approach taken in this project. Instead of considering the relative energy-intensity response functions of the spectrometer under different operating conditions it was possible to consider tha problem in terms of absolute intensities.
The reference material consists of a copper substrate containing a gold insert. Using this material 5 laboratories demonstrated with a range of cylindrical mirror analyzers and concentric hemispherical spectrometers that it is possible to produce absolute peak intensity calibrations in the AES differential mode to within +/- 4.4%. This should be compared to the 10% achieved earlier for relative intensity calibrations and should facilitate accurate comparisons between data from different instruments.