Rayleigh acoustic mode in aluminum nitride films

[object Object] Brillouin light scattering has been used for studying the propagation of the surface Rayleigh mode in AIN films grown by R.F. reactive diode magnetron sputtering on (1-1 1)-Si substrate. Since the velocity of the shear vertical wave in the film is higher than that in the substrate, the structure is of the type. fast film / slow substrate. The evolution of the Rayleigh wave has been analyzed experimentally on films of different thickness between 20 nm and 1.2 pm. The Rayleigh mode exist up to a cutoff value of the ratio h/?. For higher values of this parameter this wave becomes a leaky mode radiating energy into the substrate. Measurement of its phase velocity enabled us to determine the value of the effective elastic constant c44 of the film.