X-ray absorption near-edge structure of hexagonal ternary phases in sputter-deposited TiAlN films

Titanium aluminium nitride (TiAlN) coatings have been grown by reactive (Ar/N₂) direct-current magnetron sputtering from a Ti₅₀Al₅₀ compound target. The film composition has been quantified by ion beam analysis showing the formation of Al-rich nitrides (Ti/Al~0.3), with stoichiometric films for N2 contents in the gas mixture equal or above ~25%. The surface morphology of the films has been imaged by atomic force microscopy, showing very smooth surfaces with roughness values below 2 nm. X-ray and electron diffraction patterns reveal that the films are nanocrystalline with a wurzite (w) structure of lattice parameters larger (~2.5%) than those for w-AlN. The lattice expansion correlates with the Ti/Al ratio in stoichiometric films, which suggests the incorporation of Ti into w-AlN. The atomic environments around Ti, Al and N sites have been extracted from the X-ray absorption near-edge structure (XANES) around Ti2p, Al1s and N1s edges, respectively. The analysis of the XANES spectral lineshape and comparison with reported theoretical calculations confirm the formation of a ternary hexagonal phase.