Towards heat conduction control by phononic nanostructures

Abstract

Thermal conductivity of air-bridge silicon nanowires with various widths between 60 and 150 nm and a one-dimensional phononic crystal nanostructure are investigated at room temperature. Large reduction in thermal conductivity is observed for thinner nanowires due to more frequent surface scattering of phonons. This result indicates that the phonon transport is ballistic in the investigated systems. The 1D phononic crystal showed smaller thermal conductivity compared with a nanowire with the same width. Phononic band diagrams of various 1D phononic crystals with periods between 100 and 300 nm are calculated. The simulated phononic band gap of the cascaded architecture covers wide frequency area and ensures the proposed cascaded architecture enables the coherent control of heat conduction at cryogenic temperature.