Reduction of thermal conductance by coherent phonon scattering in two-dimensional phononic crystals of different lattice types

The impact of lattice type, period, porosity, and thickness of two-dimensional silicon phononic crystals on the reduction of thermal conductance by coherent modification of phonon dispersion is investigated using the theory of elasticity and the finite element method. Increases in the period and porosity of the phononic crystal affect the group velocity and phonon density of states and, as a consequence, reduce the in-plane thermal conductance of the structure as compared to the unpatterned membrane. This reduction does not depend significantly on the lattice type and thickness of phononic crystals. Moreover, the reduction is strongly temperature dependent and strengthens as the temperature is increased.