Intensity and energy calibration in AES: The effect of analyser modulation

To a large extent, Auger electron spectra (AES) are recorded and portrayed in the differential mode using the potential-modulation method with a phase-sensitive detector. The precise intensities of the peaks and their energy positions depend on the modulation amplitude in a nonlinear manner. This dependence, in turn, is also a function of the resolution and detailed construction of the analyser. Thus, accurate quantification and accurate assignments of peak energies depend on a detailed knowledge of the effect of analyser modulation in AES. The theoretical response of spectrometers to a Gaussian line is here analysed and compared with measurements for “singlet” peaks using several different commercial spectrometers. This shows that, in certain circumstances, the traditional methods of intensity and energy measurement can be transferred with accuracies as high as 3% and 0.05 eV, respectively. A method for calibrating the effective modulation amplitude, vital for accurate quantification, is presented in the following paper.