HYPERSONIC EIGENVIBRATIONS OF HOMOGENEOUS AND HETEROGENEOUS NANOPARTICLES

Abstract

Brillouin light scattering has been employed to investigate the eigenvibrations of homogeneous and heterogeneous nanoparticles, viz. nanocubes, oblate nanospheroids, and (cubic core)-shell nanoparticles. Finite element simulations have also been carried out to identify and elucidate the nature of the observed eigenmodes. Good agreement between experiment and calculations has been obtained. Based on calculated mode frequencies, intensities and displacement profiles, the observed spectral peaks of nanocubes were assigned to the dilatational vibrations. In addition, the particle-size dependences of the vibrational frequencies of (cubic core)-shell have been investigated. Interestingly, for the larger particles, the mode frequencies were found to scale with inverse diameter, but deviation from this linear relationship was observed for the smaller particles. The effects that the core shape and the relative hardness of the core and shell materials have on the vibrations of the core-shell as a whole have been revealed.