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Measurement of Elastic Properties of a-SiO2 by Brillouin Scattering (CAT#: STEM-ST-0108-YJL)

Introduction

Amorphous SiO2 is a substance of considerable technological importance, which displays a number of unusual features. In the glassy state, for instance, its compressibility increases with increasing pressure and its refractive index, as well as its elastic moduli, increase when the temperature rises. This archetypal glass former is made up of a threedimensional open network of SiO4 tetrahedra linked by bridging oxygens. The very strong Si-O bonds have an almost constant length, whereas Si-O-Si angles can adopt a wide range of values.




Principle

From a quantum point of view, Brillouin scattering is an interaction of light photons with acoustic or vibrational quanta (phonons), with magnetic spin waves (magnons), or with other low frequency quasiparticles interacting with light. The interaction consists of an inelastic scattering process in which a phonon or magnon is either created (Stokes process) or annihilated (anti-Stokes process). The energy of the scattered light is slightly changed, that is decreased for a Stokes process and increased for an anti-Stokes process. This shift, known as the Brillouin shift, is equal to the energy of the interacting phonon and magnon and thus Brillouin scattering can be used to measure phonon and magnon energies.

Applications

Brillouin scattering is used to determine acoustic velocities and elastic properties of a number of crystalline solids, glasses, and liquids.

Procedure

1. Sample preparation
2. Measurement by scattering detection instrument
3. Data analysis

Materials

Brillouin scattering measurement system (Brillouin spectrometer)
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