Two orders of magnitude reduction in silicon membrane thermal conductivity by resonance hybridizations

Abstract

The thermal conductivity of a freestanding single-crystal silicon membrane may be reduced significantly by attaching nanoscale pillars on one or both surfaces. Atomic resonances of the nanopillars locally and intrinsically couple with the base membrane phonon modes causing these modes to hybridize and flatten at each coupling location in the phonon band structure. The ensuing group velocity reductions, which in principle may be tuned to take place across silicon's full spectrum, lead to a lowering of the in-plane thermal conductivity in the base membrane. Using equilibrium molecular dynamics simulations, we report a staggering two orders of magnitude reduction in the thermal conductivity at room temperature by this mechanism.