Nanostructural characterization of TiN-Ni films: A XAFS study

We report on the nanostructure of Ni and N in nanocomposite TiN-Ni films using extended (EXAFS) and near-edge (NEXAFS) X-Ray absorption fine structure spectroscopies at the Ni-K and N-K edges, respectively. The Ni content in the films, as determined by Rutherford backscattering analysis, varies between 0 and 21.5 at%. The Ni-K-edge EXAFS measurements disclose that the bonding environment of Ni is amorphous in all studied films. However, the local coordination of Ni changes as a function of the chemical composition. More specifically, Ni belongs both to a pure amorphous Ni phase, where the Ni–Ni bondlength is equal to 2.46–2.47 Å (±0.01), while it also forms intermetallic TiNi bonds and the respective Ni–Ti bondlength is equal to 2.60–2.62 Å (±0.02). The Ni–Ni and Ni–Ti bondlengths are equal among all studied samples and they are independent of the Ni content and the deposition temperature. On the contrary, the total coordination number of Ni in the 1st nearest neighbor shell, i.e. the sum of Ni and Ti atoms that comprise this shell, increases linearly with the Ni content and varies between 5.4 ± 0.7 and 13.1 ± 1.1. Finally, the N-K-NEXAFS results reveal that Ti forms crystalline TiN in all studied samples, independently of the N and Ti content in the films.