Comparative study of the modelling of the spectral background of photoelectron spectra with the Shirley and improved Tougaard methods

Highlights: ► Development of spectrum processing software for XPS (Photoelectron Spectra). ► Research of both peak form and spectral background analysis of core level XP spectra. ► Comparison of the traditional Shirley background with the improved Tougaard background. ► Improvement of the Tougaard background method using new adjustable fit parameters. ► Integration of adjustable fit parameters in the inelastic electron scattering cross section. -- Abstract: A comparative study for the fitting of x-ray photoelectron spectra using different background model functions is presented. Synthetically generated test spectra and measured spectra from an SrTiO3 (STO) sample are fitted with the traditionally used Shirley background and the so-called improved Tougaard background calculated with four fit parameters of the inelastic electron scattering cross section. It was found that the results obtained with both methods are strongly different. In many cases the use of the Shirley background resulted in completely wrong component areas in spite of sometimes rather satisfying residual functions and Abbe criteria. In contrast, the improved Tougaard background gave excellent results for all wide range spectra including pronounced loss structures. The new source code of the current UNIFIT software (Version 2011 or higher) to calculate the Tougaard-background parameters was verified