Anisotropic lattice expansion and shrinkage of hexagonal TiAlN and CrAlN films

Ti1-xAlxN and Cr1-xAlxN films were synthesized by the arc ion plating method differing in the second metal contents X and investigated on their crystal structures, lattice parameters and microstructures. X-ray diffraction patterns showed that crystal structures of both Ti1-xAlxN and Cr1-x AlxN films changed from the NaCl-type (cubic structure; c-) to wurtzite-type (hexagonal structure: h-) at Al contents X = 0.6-0.7. Lattice parameters of c-Ti1-xAlxN and c-Cr1-xAlxN with Al contents X less than or equal to 0.6 uniformly decreased with respect to all lattice spacings with increasing X values. On the other hand, for h-Ti1-xAlxN and h-Cr1-xAlxN films with X greater than or equal to 0.7. anisotropic lattice expansion and shrinkage were observed with the a- and c-axes. The lattice spacing expanded in the a-direction and shrank in the c-direction by adding Ti and Cr atoms with larger atomic radius into AlN structure, respectively. (C) 2003 Elsevier Science B.V. All rights reserved.