ANISOTROPY IN RESIDUAL STRAINS AND THE LATTICE-PARAMETER OF REACTIVE SPUTTER-DEPOSITED ZRN FILMS

Lattice parameter anisotropy is a well-documented phenomenon in sputter-deposited ZrN films. The lattice parameter calculated from (111) diffraction peaks is greater than the lattice parameters calculated on the basis of other peaks. The mechanisms suggested to explain the anisotropy are discussed, and the most likely mechanism is indicated. The mechanisms considered are: (a) the elastic anisotropy of nitride films, (b) the Rhombohedral distortion, (c) selective entrapment of interstitial atoms and (d) selective growth of lattice defects. The first two mechanisms are rejected as incompatible with the experimental data. The remaining two are possible, but preference is given to the selective entrapment of interstitials. This approach is taken because it seems to explain the development of microstrains and it is in line with the X-ray technique applied to evaluate macrostrains.