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)

References

[1] Chen X, Wang Z, Ma Y. Atomistic design of high thermoelectricity on Si/Ge superlattice nanowires. Journal of Physical Chemistry, 2011, 115(42): 20696–20702

[2] Biswas K, He J, Zhang Q, Wang G, Uher C, Dravid V P, Kanatzidis M G. Strained endotaxial nanostructures with high thermoelectric figure of merit. Nature Chemistry, 2011, 3(2): 160–166

[3] Zhao L D, Hao S, Lo S H, Wu C I, Zhou X, Lee Y, Li H, Biswas K, Hogan T P, Uher C, Wolverton C, Dravid V P, Kanatzidis M G. High thermoelectric performance via hierarchical compositionally alloyed nanostructures. Journal of the American Chemical Society, 2013, 135(19): 7364–7370

[4] Mu X, Wang L, Yang X, Zhang P, To A C, Luo T. Ultra-low thermal conductivity in Si/Ge hierarchical superlattice nanowire. Scientific Reports, 2015, 5(1): 16697

[5] Qiu B, Chen G, Tian Z. Effects of aperiodicity and roughness on coherent heat conduction in superlattices. Nanoscale and Microscale Thermophysical Engineering, 2015, 19(4): 272–278

[6] Plimpton S. Fast parallel algorithms for short-range molecular dynamics. Journal of Computational Physics, 1995, 117(1): 1–19

[7] Tersoff J. Modeling solid-state chemistry: interatomic potentials for multicomponent systems. Physical Review B, Condensed Matter, 1989, 39(8): 5566–5568

[8] Ji P, Zhang Y, Yang M. Structural, dynamic, and vibrational properties during heat transfer in Si/Ge superlattices: a car-parrinello molecular dynamics study. Journal of Applied Physics, 2013, 114(23): 234905

[9] Feng X L, Li Z X, Guo Z Y. Molecular dynamics simulation of thermal conductivity of nanoscale thin silicion films. Nanoscale and Microscale Thermophysical Engineering, 2003, 7(2): 153–161

[10] Wang Z, Li Z. Research on the out-of-plane thermal conductivity of nanometer silicon film. Thin Solid Films, 2006, 515(4): 2203–2206

[11] Ju Y S, Goodson K E. Phonon scattering in silicon films with thickness of order 100 nm. Applied Physics Letters, 1999, 74(20): 3005–3007

[12] Luo T, Lloyd J R. Ab initio molecular dynamics study of nanoscale thermal energy transport. Journal of Heat Transfer, 2008, 130(12): 122403

[13] Ji P, Zhang Y. First-principles molecular dynamics investigation of the atomic-scale energy transport: from heat conduction to thermal radiation. International Journal of Heat and Mass Transfer, 2013, 60(1): 69–80

[14] Hu M, Poulikakos D. Si/Ge superlattice nanowires with ultralow thermal conductivity. Nano Letters, 2012, 12(11): 5487–5494

[15] Huis in't Veld B, Overmeyer L, Schmidt M,Wegener K, Malshe A, Bartolo P. Si/Ge micro additive manufacturing using ultra short laser pulses. CIRP Annals—Manufacturing Technology, 2015, 64: 701–724

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).

RIGHTS & PERMISSIONS

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