Prediction and identification of point defect fingerprints in X-ray photoelectron spectra of TiN x with 1.18 ≤ 𝑥 ≤ 1.37

We investigate the effect of selected N and Ti point defects in B1 TiN on N 1s and Ti 2p
binding energies (BE) through experiments and ab initio calculations. X-ray photoelectron spectroscopy (XPS) measurements of TiNx films with 1.18
1.37 reveal additional N 1s spectral components at lower binding energies. Ab initio calculations predict that these components are caused by either Ti vacancies, which induce an N 1s BE shift of
eV in their first N neighbors, and/or N tetrahedral interstitials, which have their N 1s BE shifted by
eV and shift the BE of their first N neighbors by
eV. However, based on ab initio data the tetrahedral N interstitial is estimated to be unstable at room temperature. We, therefore, unambiguously attribute the N 1s spectral components at lower BE in Ti-deficient TiNx thin films to the presence of Ti vacancies. Furthermore, it is demonstrated that the vacancy concentration in Al-capped Ti-deficient TiNx can be quantified with the proposed correlative method based on measured and predicted BE data. Our work highlights the potential of ab initio-guided XPS measurements for detecting and quantifying point defects in B1 TiNx.