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 elasti c constants of a single transparent film of hexagonal symmetry, in the micron range of thicknesses. Measurements have been performed on a po lyclystalline ZnO film, about 1.3 mu m thick, supported by a Si substr ate. 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 cons tants, namely c(13), c(33) and c(44). can be then obtained from detect ion of the Rayleigh surface mode and of the longitudinal bulk wave pro pagating at different angles from the surface normal.