University of Birmingham > Talks@bham > Metamaterials Research Group Seminars > Modification of thermal conductivity and phonon dispersion relation by means of phononic crystals

Modification of thermal conductivity and phonon dispersion relation by means of phononic crystals

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If you have a question about this talk, please contact Dr Miguel Navarro-Cia.

Phononic crystals (PnCs) are periodic structures made of materials with different elastic properties, with lattice spacing comparable to the acoustic wavelength. Engineering of the phonon dispersion relation allows modifying material properties in a controlled manner. In this context, silicon nanomembranes appear as an excellent system to study the effect of the reduction of the characteristic size on the phonon dispersion relation and its influence on phonon propagation and material properties such as thermal transport. The latest investigations on the thermal properties of silicon, have pointed to nanostructuring as a highly efficient approach to acoustic phonon engineering. Also heat conduction in silicon can be engineered by means of sub-micrometer patterning on free-standing membranes. Tunable thermal properties make these structures good candidates for integrated heat management devices, for instance for waste heat recovery or heat rectification. However, possible applications require detailed thermal characterization which, up to now, has been an experimental challenge.

In this work we use the contactless two-laser Raman thermometry to measure thermal transport and Brillouin spectroscopy to study phonon dispersion relation of periodic porous membranes. The aim of the study is to understand and control the behaviour of phonons, by means of PnCs. The target is to minimize the thermal conductivity by phonon engineering. In particular, we are interested in the influence of volume-to-surface ratio on the thermal conductivity and air convection losses.

This talk is part of the Metamaterials Research Group Seminars series.

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