A complete and self-consistent evaluation of XPS spectra of TiN

The electron configuration in single crystalline (sc-)titanium nitride (TiN) has been quantitatively studied using angle resolved X-ray photoelectron spectroscopy (AR-XPS). All samples were fabricated and transferred in situ so that only minimal surface contaminations were observed. The residual oxygen contamination was separated from the bulk information by extrapolating angle resolved measurements. Special attention is given to the quantitative evaluation of the spectra based on basic principles. Shake-up features are observed on core level lines and appear due two final ionized states. The ratio of this shake-up and the main Ti 2p energy line are investigated in this paper. In order to quantify this shake-up a precise evaluation is required. Here we present an approach to evaluate the XPS spectra of the Ti 2p photoemission line in TiN in a self-consistent manner that accounts for all features observable in an energy window of 80 eV. The evaluation considers the appropriate Tougaard background correction, shake-up features as well as surface and bulk plasmons. The ratio of the Ti 2p_1/2 and Ti 2p_3/2 and the corresponding peaks in the energy loss features fulfill the requirements given by quantum mechanics. The energy loss ΔE due to the shake-up process and the shake-up ratio have been determined quantitatively for oxygen-free bulk titanium nitride. The origin of the shake-up, its intensity and energy difference ΔE are explained by a two electron excitation process.