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arXiv · 1505.05766

Crystal structure dependent thermal conductivity in two-dimensional phononic crystal nanostructures

Junki Nakagawa·Yuta Kage·Takuma Hori·Junichiro Shiomi·Masahiro Nomura
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Abstract

Thermal phonon transport in square- and triangular-lattice Si phononic crystal (PnC) nanostructures with a period of 300 nm was investigated by measuring the thermal conductivity using micrometer-scale time-domain thermoreflectance. The placement of circular nanoholes has a strong influence on thermal conductivity when the periodicity is within the range of the thermal phonon mean free path. A staggered hole structure, i.e., a triangular lattice, has lower thermal conductivity, where the difference in thermal conductivity depends on the porosity of the structure. The largest difference in conductivity of approximately 20% was observed at a porosity of around 30%. This crystal structure dependent thermal conductivity can be understood by considering the local heat flux disorder created by a staggered hole structure. Numerical simulation using the Monte Carlo technique was also employed and also showed the lower thermal conductivity for a triangular lattice structure. Besides gaining a deeper understanding of nanoscale thermal phonon transport, this information would be useful in the design of highly efficient thermoelectric materials created by nanopatterning.

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Junki Nakagawa, Yuta Kage, Takuma Hori, Junichiro Shiomi, Masahiro Nomura. 2015-05-21. Crystal structure dependent thermal conductivity in two-dimensional phononic crystal nanostructures. https://arxiv.org/abs/1505.05766

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