INTERCOMPARISON OF ALGORITHMS FOR BACKGROUND CORRECTION IN XPS

In the present interlaboratory comparison, the consistency and validity of the Shirley, straight-line and Tougaard methods for determination of peak intensities from measured XPS spectra have been studied by analysis of data on Au and Ni taken at eight laboratories, The reproducibility of the individual measuring systems was determined to be 2-6%, The RMS scatter around their mean values of the ratio of the peak intensity to the Au 4d peak intensity was 6% for the Tougaard method, 9-10% for the Shirley method and 8-9% for the straight-line method, The increase in root mean square (RMS) scatter of data due to data being recorded in different laboratories amounts to 3-4%, independent of the method applied for background correction, The RMS deviation from theory of intensity ratios of peaks from Ni and Au to the Au 4d peak intensity is 14% for the Tougaard method, 33% for the Shirley method and 31% for the straight-line method, The absolute accuracy of the methods cannot be established to better than the accuracy on the theoretical peak intensity ratios and the uncertainty in the energy dependence of the analyser response function, It is, however, reasonable to expect the combined uncertainty of these factors to be at least 10-15%, The peak intensity ratios obtained with the Tougaard method then falls within the expected accuracy of the theoretical ratios.