Tunable Superlattice In-plane Thermal Conductivity based on Asperity Sharpness at Interfaces: Beyond Ziman’s Model of Specularity

Ali Rajabpour (1) , Yann Chalopin (2) , M. Vaez Allaei , Farshad Kowsary , Sebastian Volz (2)

1 Department of Mechanical Engineering
2 EM2C - Laboratoire d'Énergétique Moléculaire et Macroscopique, Combustion

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.

Domaines: Science des matériaux [cond-mat.mtrl-sci]; Thermique [physics.class-ph]; Micro et nanotechnologies/Microélectronique

Ali Rajabpour, Yann Chalopin, M. Vaez Allaei, Farshad Kowsary, Sebastian Volz. Tunable Superlattice In-plane Thermal Conductivity based on Asperity Sharpness at Interfaces: Beyond Ziman’s Model of Specularity. Journal of Applied Physics, 2011, 110 (11), pp.113529. ⟨10.1063/1.3665408⟩. ⟨hal-01285833⟩