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.