Elastic Waves in Nano-Columnar Porous 4H-SiC Measured by Brillouin Scattering

Abstract

We report measured and calculated frequencies of elastic waves propagating in columnar porous 4H-SiC, an analytically tractable system. The sample was prepared using photo-electrochemical etching followed by mechanical polishing. The frequencies were measured using Brillouin scattering spectroscopy in backscattering geometry. The effective elastic constants, ordinary and extraordinary indices of refraction, and mass density, all obtained using effective medium models, are used to calculate the frequencies. Although the quasistatic limit is not strongly satisfied, the agreement between the measured and calculated values is good.

Brillouin Scattering and its Application in Geosciences

“…Brillouin scattering measurements of acoustic velocities of heterogeneous nanoscale composite materials allows testing of the different models to describe the effective elastic properties of highly heterogeneous media. In the case of nanoporous 4H-SiC, Devaty et al (2010) verified the correctness of the effective medium model in the case of arrays of columnar 20 nm diameter pores in quasi-hexagonal arrangement.…”

“…Thorough investigations of Brillouin spectra from heterogeneous micro-aggregates have elucidated the details of their dispersion relation in the GHz regime, including fine details of localized eigenmodes of the particles of the dispersed components (Kriegs et al 2004). In the case of predefined microstructure, Brillouin scattering has been successfully used to determine the effective elastic properties of the composite by applying effective medium models (e.g., Devaty et al 2010). These promising results suggest that Brillouin scattering could be used to infer properties of unknown materials when they form microstructurally well-characterized aggregates with materials of known elastic properties at extreme conditions.…”