Nano-structured titanium and aluminium nitride coatings: Study by grazing incidence X-ray diffraction and X-ray absorption and anomalous diffraction

Titanium and aluminium nitride thin films, Ti1 − xAlxN (x = 0, x = 0.5, x = 0.68), deposited by reactive magnetron sputtering on silicon substrates are investigated by combining two different X-ray diffraction experiments carried out using synchrotron radiation. Grazing-incidence X-ray diffraction and Ti K-edge diffraction anomalous near edge structure spectroscopy provide information on the micro- and nano-structure of the films respectively, which play a crucial role in the functionality of coatings. The spectroscopic data of Ti0.50Al0.50N film show that Ti atoms in crystallized domains and grain boundaries are all in octahedral cubic local order, but their growth mode is quite different. It is found that the crystallized part of the Ti0.50Al0.50N film has a single-crystalline nature, whereas the TiN one presents a fibrillar microstructure. For Ti0.32Al0.68N film, grazing-incidence X-ray diffraction provides information on the uniaxial texture along the [001] direction of the hexagonal lattice. A sharp Ti K pre-edge peak is observed in diffraction anomalous near edge spectrum that definitely shows that Ti atoms are incorporated in the hexagonal lattice of those fibrillar domains. Moreover, the difference observed between Ti K-edge diffraction anomalous and X-ray absorption pre-edge regions proves that a significant part of Ti atoms is located in nanocrystallites with cubic symmetry outside of the crystallized domains.

► We study nano and micro-structures of TiN, Ti0.50Al0.50N and Ti0.32Al0.68N films. ► Anomalous diffraction solves the crystallized part regardless of grain boundaries. ► TiN microstructure is fibrillar, Ti0.5Al0.5N presents single crystalline domains. ► For Ti0.32Al0.68N, Ti atoms are located in nanocrystallites with cubic symmetry. ► Diffraction and spectroscopy supply additional information on micro-nanostructure.