Evaluation of uncertainties in X‐ray photoelectron spectroscopy intensities associated with different methods and procedures for background subtraction. II. Spectra for unmonochromated Al and Mg X‐rays

Abstract

We report uncertainties in X-ray photoelectron spectroscopy (XPS) intensities arising from commonly used methods and procedures for subtraction of the spectral background. These uncertainties were determined from a comparison of XPS intensities reported by volunteer analysts and the corresponding intensities expected for a set of simulated XPS spectra. We analyzed peak intensities from 16 sets of data (submitted from 15 institutions) for a group of 12 spectra that had been simulated for an unmonochromated Al-Kα source and similar intensities from 20 sets of data (submitted from 17 institutions) that had been simulated for an unmonochromated Mg-Kα source. Each reported intensity was compared with an expected intensity for the particular integration limits chosen by each analyst and known from the simulation design. We present ratios of the reported intensities to the expected intensities for the background-subtraction methods chosen by the analysts. These ratios were close to unity in most cases, as expected, but deviations were found in the results from some analysts, particularly if shakeup was present. We showed that better results for the Shirley and Tougaard backgrounds were obtained when analysts determined peak intensities over certain energy ranges or integration limits. We then were able to suggest integration limits that should be a useful guide in the determination of peak intensities for other XPS spectra. The use of relatively narrow integration limits with the Shirley and linear backgrounds, however, will lead to measures of peak intensity that are less than the total intensities. Although these measures may be satisfactory for some quantitative analyses, errors in quantitative XPS analyses can occur if there are changes in XPS lineshapes or shakeup fractions with change of chemical state. The use of curve-fitting equations to fit an entire spectrum will generally exclude the shakeup contribution to the intensity of the main peak, and any variation in the shakeup fraction with change of chemical state will not be taken into account.

Effect of molybdenum and tungsten polyoxometalates on the composition of surface layers and electrochemical behavior of stainless steel in sulfuric acid

“…The integrated areas under the peaks are assessed after Shirley background subtraction [28]. The XP Fe2p spectrum and, to a slightly smaller extent, the Cr2p spectrum are considerably complicated by the presence of different oxidation states of iron and satellite peaks that can result in quantitative analysis errors [29][30][31][32][33][34][35][36][37][38][39][40][41]. To determine the contributions of oxide and metallic iron and chromium, the curve fitting method was used.…”

Development of standards for reliable surface analyses by ISO technical committee 201 on surface chemical analysis

“…Data in the standard format can also be imported into instrumental or other software, e.g. for tests of algorithms used to determine peak intensities . A similar format has been developed for SPM (ISO 28600, shown in section D of Table ).…”