RANDOM UNCERTAINTIES IN AES AND XPS .2. QUANTIFICATION USING EITHER RELATIVE OR ABSOLUTE MEASUREMENTS

Often, peak intensity measurements are quantified by using relative sensitivity factors to give the composition of a surface in percentage terms. This process affects the estimation of uncertainties; the uncertainty in the final quantification depends in a complex way on a sum involving the squares of the uncertainties in the measures for each element. We examine quantification in detail, and apply Bayesian statistical methods to this problem for the first time. We find that if the intensities are quantified by an absolute method rather than a relative one, the final uncertainties involve sums of the reciprocals of the squares of these individual uncertainties. Thus, the combination of uncertainties in quantification by an absolute method can improve the accuracy of the final quoted composition, whereas the combination of uncertainties in quantification by sensitivity factors always reduces the accuracy.