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

Heat conduction in silicon can be effectively reduced by means of periodic patterning of free-standing membranes. In this work we show a straightforward method for fabrication of free-standing phononic crystals based on thin silicon membranes. We use the contactless two-laser Raman thermometry method to measure thermal conductivity of the hexagonal phononic crystals. The aim of the study is to understand and control the behaviour of phonons in phononic crystals, with the target of minimizing the thermal conductivity. In particular, we are interested in the influence of the surface-to-volume ratio on the thermal conductivity.