BRILLOUIN-SCATTERING DETERMINATION OF THE WHOLE SET OF ELASTIC-CONSTANTS OF A SINGLE TRANSPARENT FILM OF HEXAGONAL SYMMETRY

In this work it is shown that the Brillouin light scattering technique can be successfully applied for determining the five effective elastic constants of a single transparent film of hexagonal symmetry, in the micron range of thicknesses. Measurements have been performed on a polyclystalline ZnO film, about 1.3 mu m thick, supported by a Si substrate. A major result of this work is that the elastic constant c(66) is selectively determined for the first time from detection of the shear horizontal mode travelling parallel to the film surface. Similarly, a selective determination of c(11) is attained from observation of the longitudinal mode guided by the film. The three remaining elastic constants, namely c(13), c(33) and c(44). can be then obtained from detection of the Rayleigh surface mode and of the longitudinal bulk wave propagating at different angles from the surface normal.