Complete elastic characterization of a silica layer by Brillouin scattering

Brillouin scattering, the scattering of light by ultrasonic waves, offers the possibility to probe the velocity of acoustic modes at sub-micrometric wavelength. From the acoustic properties the elastic properties can be derived. In the case of transparent films both bulk and surface acoustic waves can be measured. Brillouin scattering has been exploited to characterize a silica layer of micrometric thickness, thermally grown on a silicon substrate. The observation of different scattering geometries allowed to measure both the Young modulus and Poisson's ratio of the silica film, together with its refractive index