Impacts of cone-structured interface and aperiodicity on nanoscale thermal transport in Si/Ge superlattices

Abstract

Si/Gesuperlattices are promising thermoelectric materials to convert thermal energy into electric power. The nanoscale thermal transport in Si/Gesuperlattices is investigated via molecular dynamics (MD) simulation in this short communication. The impact of Si and Ge interface on the cross-plane thermal conductivity reduction in the Si/Gesuperlattices is studied by designing cone-structured interface and aperiodicity between the Si and Ge layers. The temperature difference between the left and right sides of the Si/Gesuperlattices is set up for nonequilibrium MD simulation. The spatial distribution of temperature is recorded to examine whether the steady-state has been reached. As a crucial factor to quantify thermal transport, the temporal evolution of heat flux flowing through Si/Gesuperlattices is calculated. Compared with the even interface, the cone-structured interface contributes remarkable resistance to the thermal transport, whereas the aperiodic arrangement of Si and Ge layers with unequal thicknesses has a marginal influence on the reduction of effective thermal conductivity. The interface with divergent cone-structure shows the most excellent performance of all the simulated cases, which brings a 33% reduction of the average thermal conductivity to the other Si/Gesuperlattices with even, convergent cone-structured interfaces and aperiodic arrangements. The design of divergent cone-structured interface sheds promising light on enhancing the thermoelectric efficiency of Si/Ge based materials.

Keywords

thermoelectric material / thermal transport / Si/Gesuperlattics / molecular dynamics (MD)

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Acknowledgment

This work was supported by the US National Science Foundation (Grant No. CBET-133611); the National Natural Science Foundation of China (Grant No. 51705234) and the Presidential Postdoctoral Fellowship of the Southern University of Science and Technology, and the project funded by China Postdoctoral Science Foundation (Grant No. 2017M612653).

版权

2018 Higher Education Press and Springer-Verlag GmbH Germany, part of Springer Nature