Molecular Dynamics Simulations of the Thermal Conductivity of Silicon-Germanium and Silicon-Germanium-Tin Alloys

Zan Wang,Y W Ruan,W K Zhao,H Wang,X Y Cai,Hassan Karimi-Maleh

doi:10.1155/2021/6675159

Abstract

In this work, we investigate the thermal conductivity properties of Si 1 − x Ge x and Si 0.8 Ge 0 Sn 2 y alloys. The equilibrium molecular dynamics (EMD) is employed to calculate the thermal conductivities of Si 1 − x Ge x alloys when x is different at temperatures ranging from 100 K to 1100 K. Then nonequilibrium molecular dynamics (NEMD) is used to study the relationships between y and the thermal conductivities of Si 0.8 Ge 0.2 Sn 2 y alloys. In this paper, Ge atoms are randomly doped, and tin atoms are doped in three distributing ways: random doping, complete doping, and bridge doping. The results show that the thermal conductivities of Si 1 − x Ge x alloys decrease first, then increase with the rise of x , and reach the lowest value when x changes from 0.4 to 0.5. No matter what the value of x is, the thermal conductivities of Si 1 − x Ge x alloys decrease with the increase of temperature. Thermal conductivities of Si 0.8 Ge 0.2 alloys can be significantly inhibited by doping an appropriate number of Sn atoms. For the random doping model, thermal conductivities of Si 0.8 Ge 0.2 Sn y alloys approach the lowest level when y is 0.10. Whether it is complete doping or bridge doping, thermal conductivities decrease with the increase of the number of doped layers. In addition, in the bridge doping model, both the number of Sn atoms in the [001] direction and the penetration distance of Sn atoms strongly influence thermal conductivities. The thermal conductivities of Si 0.8 Ge 0.2 Sn y alloys are positively associated with the number of Sn atoms in the [001] direction and the penetration distance of Sn atoms.

Highlights

Attention to metal nanomaterials and their applications can be creating a new approach in science [1,2,3]
When x increases from 0.5 to 1.0, the thermal conductivities increase too, which suggests that the enhancement of thermal conduction of Ge atoms surpasses the hindrance of lattice point defect
We investigate the thermal features of alloys with three Sn doping modes as random doping, complete doping, and bridge doping

Summary

Introduction

Attention to metal nanomaterials and their applications can be creating a new approach in science [1,2,3]. Since SiGe alloys have the advantages of good stability, high melting point, and strong oxidation resistance, they are widely used in spacecraft radioisotope batteries, power generators for micro devices, etc To improve their thermoelectric performance, it is necessary to reduce thermal conductivities of SiGe alloys. Molecular dynamics (MD) is a feasible micro-nanoscale research method based on classical Newtonian mechanics [13, 14] and is suitable for the study of heat conduction of SiGe alloys with dopants at the micro-nanoscale [15,16,17,18,19,20,21,22,23]. The expression of aSi0:8Ge0:2Sny is obtained as follows: aSi0:8Ge0:2Sny = aGe + 0:8 × ΔSiGe + 0:8 × ð0:2 + yÞ ð5Þ × θGeSi + ΔSnGe × y + θGeSn × y: In this work, the NEMD method was used to simulate the thermal conductivities of Si0:8Ge0:2Sny in [100] direction. Φ × ∇T ð7Þ where λ is the thermal conductivity, Φ is the value of heat flow, A is the cross-sectional area perpendicular to the direction of heat flow, and ∇T is the temperature gradient

Results and Discussion

Eight-layer bridge doping

Conclusions

Disclosure