Elastic properties of TiN/(VxNb1−x)N superlattices measured by Brillouin scattering

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Abstract
Brillouin scattering measurements have been carried out on single‐crystal lattice‐matched TiN/(V0.6Nb0.4)N and mismatched TiN/NbN superlattices. Measured surface wave velocities were found to be independent of superlattice wavelength over the entire range investigated, 1.5–30 nm, and were averages of the measured velocities of pure homogeneous TiN, NbN, and (V0.6Nb0.4)N. These results indicate that there is no anomaly in the C44 elastic constant. X‐ray diffraction results from the superlattices indicated that the average lattice spacing did not vary with wavelength. This is consistent with previous observations where elastic anomalies were related to changes in lattice spacing. The absence of a correlation between the C44 elastic constant and previously reported hardness enhancements indicates that the latter are not caused by anomalies in C44; they could, however, be correlated with other elastic moduli.