Aluminum incorporation in $Ti1−xAlxN$ films studied by x-ray absorption near-edge structure

The local bonding structure of titanium aluminum nitride $(Ti1−xAlxN)$ films grown by dc magnetron cosputtering with different AlN molar fractions $(x)$ has been studied by x-ray absorption near-edge structure (XANES) recorded in total electron yield mode. Grazing incidence x-ray diffraction (GIXRD) shows the formation of a ternary solid solution with cubic structure $(c-Ti1−xAlxN)$ that shrinks with the incorporation of Al and that, above a solubility limit of $x∼0.7$⁠, segregation of $w$-AlN and $c-Ti1−xAlxN$ phases occurs. The Al incorporation in the cubic structure and lattice shrinkage can also be observed using XANES spectral features. However, contrary to GIXRD, direct evidence of $w$-AlN formation is not observed, suggesting a dominance and surface enrichment of cubic environments. For $x>0.7$⁠, XANES shows the formation of Ti–Al bonds, which could be related to the segregation of $w$-AlN. This study shows the relevance of local-order information to assess the atomic structure of $Ti1−xAlxN$ solutions.