Journal
PHYSICAL REVIEW X
Volume 7, Issue 2, Pages -Publisher
AMER PHYSICAL SOC
DOI: 10.1103/PhysRevX.7.021024
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Funding
- Materials research by Information Integration Initiative (MI2I) project
- CREST from Japan Science and Technology Agency (JST) [JPMJCR16Q5]
- KAKENHI [16H04274, 15K17982]
- Information Initiative Center at Hokkaido University and Academic Center for Computing and Media Studies at Kyoto University through the HPCI System Research Project [hp160161]
- Grants-in-Aid for Scientific Research [17J08427, 16H04274, 15K17982] Funding Source: KAKEN
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We demonstrate optimization of thermal conductance across nanostructures by developing a method combining atomistic Green's function and Bayesian optimization. With an aim to minimize and maximize the interfacial thermal conductance (ITC) across Si-Si and Si-Ge interfaces by means of the Si/Ge composite interfacial structure, the method identifies the optimal structures from calculations of only a few percent of the entire candidates (over 60 000 structures). The obtained optimal interfacial structures are nonintuitive and impacting: the minimum ITC structure is an aperiodic superlattice that realizes 50% reduction from the best periodic superlattice. The physical mechanism of the minimum ITC can be understood in terms of the crossover of the two effects on phonon transport: as the layer thickness in the superlattice increases, the impact of Fabry-Perot interference increases, and the rate of reflection at the layer interfaces decreases. An aperiodic superlattice with spatial variation in the layer thickness has a degree of freedom to realize optimal balance between the above two competing mechanisms. Furthermore, the spatial variation enables weakening the impact of constructive phonon interference relative to that of destructive interference. The present work shows the effectiveness and advantage of material informatics in designing nanostructures to control heat conduction, which can be extended to other nanostructures and properties.
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