Tunable superlattice in-plane thermal conductivity based on asperity sharpness at interfaces: Beyond Ziman's model of specularity
A Rajabpour and SMV Allaei and Y Chalopin and F Kowsary and S Volz, JOURNAL OF APPLIED PHYSICS, 110, 113529 (2011).
We prove that interfacial asperity sharpness allows for tuning superlattice in-plane thermal conductivity below or above the limit of high roughness derived from the Lucas-Ziman (LZ) model. Whereas LZ's model predicts molecular dynamic (MD) results of Lennard-Jones superlattices for small asperities, it has to be modified with a roughness-and sharpness-dependent layer thickness to remain relevant at higher roughness. For the case of sharpest asperities, the modified LZ model still fails, and ray-tracing computations matching MD data reveal a phonon-trap effect in the asperity valleys. This behavior scales with the Knudsen number and should appear at the micron scale in large mean- free-path crystals, such as silicon. (C) 2011 American Institute of Physics. doi:10.1063/1.3665408
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