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ENERGY AND INTENSITY CALIBRATIONS FOR XPS AND AES

Objective



The aims of the projects were to provide traceable energy and intensity scales for X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES).

RESULTS

i) Energy scales

For both XPS and AES energy scales traceable to the UK national voltage standard have been realised by the accurate measurement of the positions of strong characteristic peaks of gold, silver and copper. When applied via intercomparison, the XPS scale demonstrated that on commercial machines the principle sources of errors were in the setting of the zero and the establishment of scaling factors. The corresponding scale for AES reduced the scatter seen in an ASTM intercomparison by more than a factor of 5 for all instruments surveyed and a factor of 17 for high resolution instruments.

ii) Energy-intensity response functions

The response function of an electron spectrometer to a given flux of electrons depends upon their energy and the details of the spectrometers construction. To enable individual XPS spectrometer's relative energy-intensity response functions to be determined a well defined procedure again based on the characteristic peaks of Au, Ag and Cu was derived. Using this procedure it was demonstrated in an intercomparison that results from different instruments could, for the first time, be compared to within one standard deviation of 4%. For the AES case a fully instrumented electron spectrometer capable of determining absolute spectral intensities was developed. The intensity scale derived with this instrument enabled 38 laboratories using a wide range of equipments to reproduce quantitative analyses for Au, Ag and Cu to within 3% over the energy range 10 to 2500 ev and 2% over the range 100 to 1000 ev when using the direct mode. However when working in the differential mode the agreement degraded to worse than 10% (see Project 287).The use of the absolute spectrometer has now been extended to the XPS case and a second intercomparison has started to determine the reproducibility of the absolute scale for a wide range of instruments. This will be completed by the end of 1990.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

National Physical Laboratory (NPL)
Address
Queen's Road
TW11 0LW Teddington
United Kingdom