Optimization of Si PnC MEMS nanowires for ultra-low thermal conductivity

We report the fabrication and characterization of suspended Si nanostructures with phononic crystals (PnCs), the so called Si nanowires. Increased phonon scattering caused by nanowire edges and PnCs results in significant reduction in thermal conductivity and therefore extreme thermal isolation, which would be useful for silicon based thermoelectric devices. The thermal conductivity of the suspended silicon nanowires is characterized using Raman spectroscopy, where we measure the temperature of different locations of the fabricated Si nanowires. PnCs contributing to significantly decreased thermal conductivity are strong candidates for a range of future Micro-electromechanical systems (MEMS) device applications where extreme thermal isolation is desired. An ultra-low thermal conductivity of 2.4 W/m.K is obtained with Si PnCs nanowires in this work.