RESUMEN

We report on the first systematic study of phonon propagation in nanostructured composite polymer multilayer films as a function of periodicity and composition using Brillouin light scattering and numerical simulations. The high sensitivity of phonon dispersion to structure and composition allows the probing of the mechanical properties down to the single-layer level. We observe a strikingly different dependence of the longitudinal and shear moduli on confinement effects in the polymer nanolayers. In addition, temperature dependent measurements of sound velocities reveal the presence of distinct glass transition temperatures, indicative of phonon localization in films with large layer thicknesses in agreement with theoretical predictions.

Asunto(s)

Membranas Artificiales , Modelos Químicos , Nanoestructuras/química , Nanoestructuras/ultraestructura , Nanotecnología/métodos , Polímeros/química , Simulación por Computador , Elasticidad , Dureza , Ensayo de Materiales , Tamaño de la Partícula , Estrés Mecánico , Vibración

RESUMEN

In this Letter we propose the use of hypersonic phononic crystals to control the emission and propagation of high frequency phonons. We report the fabrication of high quality, single crystalline hypersonic crystals using interference lithography and show that direct measurement of their phononic band structure is possible with Brillouin light scattering. Numerical calculations are employed to explain the nature of the observed propagation modes. This work lays the foundation for experimental studies of hypersonic crystals and, more generally, phonon-dependent processes in nanostructures.