Absolute calibration of an X-ray photoelectron spectrometer

The fundamental equations of XPS technique for instruments without retardation and with spherical analyzer are outlined and the usual calibration with defined energy level is discussed, including the relativistic correction. Based on these considerations a new method is developed. For calibration two items are required: (1) the true electron energy as function of the sphere voltage and (2) a defined zero point for the scale of binding energy. The first step is realized by the evaluation of line shifts due to defined bias voltages between sample and spectrometer entrance slit. The second step deals with the experimental determination of the Fermi level. The calibration was performed with Pd and Au. The accuracy of measured binding energies when applying the absolute calibration method has been found to be at least +-0.2 eV. The method is also applicable to instruments with spherical analyzers, working at variable sphere voltage and constant retardation. (Auth.)