BS ISO 18118:2015 pdf download – Surface chemical analysis — Auger electron spectroscopy and X-ray photoelectron spectroscopy — Guide to the use of experimentally determined relative sensitivity factors for the quantitative analysis of homogeneous materials.
6 Measurement conditions 6.1 General The same measurement conditions (for example, instrumental configuration, sample orientation, and instrumental settings) shall be used for the measurement with the unknown sample as those chosen for the ERSF measurements. Particular attention shall be given to the following parameters. 6.2 Excitation source The incident-electron energy in AES and the X-ray source in XPS shall be the same for the measurement of the unknown sample as that chosen for the measurement of the ERSFs. 6.3 Energy resolution Unless peak areas are used to measure the signal intensities, the energy resolution of the electron-energy analyser (that is determined by choice of aperture sizes, pass energy, or retardation ratio) shall be the same for the unknown-sample measurement as for the measurement used to generate the ERSFs. [5] 6.4 Energy step and scan rate The size of the energy step (energy per channel) used to acquire spectral data and the spectral scan rate shall be chosen so that there is negligible spectral distortion in the acquired data for the selected energy resolution. 6.5 Signal intensity The incident-electron current (in AES) or the X-ray intensity (in XPS) shall be adjusted together with the voltage applied to the detector so that the measured signal intensity is proportional to the incident current or X-ray intensity to within 1 % as described in ISO 21270. Alternatively, the measured signal intensity that is corrected for counting losses as described in ISO 21270 shall be proportional to the incident current or X-ray intensity to within 1 %.
7 Data-analysis procedures The same procedures shall be used for the analysis of the spectra measured for the unknown sample and for the ERSF measurements. To obtain a peak area or a peak height from a measured direct spectrum, a background shall be chosen and subtracted from the measured spectrum (see Reference [11]). The backgrounds most commonly used for this purpose [12] are a linear background, a Shirley background, [13] or a Tougaard background. [14] In AES, it is often convenient to measure a peak-to-peak height or a peak-to-background height in a differential spectrum. The differential spectrum can be recorded (in analogue detection instruments) or a measured direct spectrum can be numerically differentiated for this purpose. The same numerical procedure and choices shall be made in the differentiation of the spectra for the unknown sample and for the reference samples used to determine the ERSFs. [11][15] See also 6.7. NOTE 1 Details of background-subtraction procedures are given in Reference [11]. NOTE 2 Details of peak attenuation in numerical differentiation and of the Savitzky and Golay differentiation method in AES can be obtained from Reference [9] and Reference [10]. NOTE 3 Reference [16] gives information on procedures to obtain consistent results in the use of differentiation for measurements with different chemical states of an element. This reference provides similar information for the determination of peak areas.