An empirical electron spectrometer transmission function for applications in quantitative XPS

Abstract

AbstractThe use of XPS data for accurate elemental quantitation requires that the transmission function of the electron spectrometer be known. Often, the dependence on electron kinetic energy (Ek) and spectrometer pass energy (Ea) are treated as separable functions. This is inadequate for the comparison of data taken with different pass energies. We have measured the variation of signal intensity as a function of Ea and Ek using the VG Escalab MK II spectrometer under constant analyzer energy conditions. Results from three independent laboratories on a variety of samples are in good agreement. The combined data have been used to develop an empirical formula that relates the signal intensity to the electron kinetic energy and spectrometer pass energy. The non‐separable relationship that we obtain is of the form Relative sensitivity factors used for XPS quantitation depend on the instrument transmission function. It is not adequate to use an invariant table of factors for all analyser conditions, as is assumed by many XPS data systems. The above empirical formula leads to simple calculations of elemental sensitivity factors at different spectrometer pass energies. It will be demonstrated that this can facilitate comparison of small‐area and large‐area XPS data and quantitative analysis of complex materials where it is desirable to measure minor components at high pass energy.