Lamb waves in unsupported thin films: A Brillouin-scattering study

Abstract

Using Brillouin scattering we have succeeded in observing the normal modes of vibration of unsupported films in a region where the dispersion relationship is quadratic. Extremely low-lying excitations were observed in thin films with thicknesses as small as 200 Å. Contrary to what has been found in work on supported films, we are able to extract information on a number of the elastic moduli because the measured velocities in very thin films do not depend on the properties of the substrate. This technique should be a valuable addition to the tools which can be used in the study of materials in thin-film form. DOI: http://dx.doi.org/10.1103/PhysRevLett.58.1216 © 1987 The American Physical Society