Chen Xue-Kun, Pang Min, Chen Tong, Du Dan, Chen Ke-Qiu
School of Mathematics and Physics, University of South China, Hengyang 421001, China.
School of Energy and Mechanical Engineering, Jiangxi University of Science and Technology, Nanchang 330013, China.
ACS Appl Mater Interfaces. 2020 Apr 1;12(13):15517-15526. doi: 10.1021/acsami.9b22498. Epub 2020 Mar 19.
Graphene/hexagonal boron nitride (h-BN) heterostructures assembled by van der Waals (vdW) interactions show numerous unique physical properties such as quantum Hall effects and exotic correlated states, which have promising potential applications in the design of novel electronic devices. Understanding thermal transport in such junctions is critical to control the performance and stability of prospective nanodevices. In this work, using nonequilibrium molecular dynamics simulations, we systematically investigate the thermal transport in asymmetric graphene/h-BN vdW heterostructures. It is found that the heat prefers to flow from the monolayer to the multilayer regions, resulting in a significant thermal rectification (TR) effect. To determine the optimum conditions for TR, the influences of sample length, defect density, asymmetric degree, ambient temperature, and vdW interaction strength are studied. Particularly, we found that the TR ratio could be improved by about 1 order of magnitude via increasing the coupling strength from 1 to 10, which clearly distinguishes from the commonly held notion that the TR ratio is practically insensitive or even decreasing with the interaction strength. Detailed spectral analysis reveals that this unexpected increase of the TR ratio can be attributed to heavily modified phonon properties of encased graphene due to enhanced interlayer coupling. Our results elucidate the importance of vdW interactions to heat conduction in nanostructures.
通过范德华（vdW）相互作用组装而成的石墨烯/六方氮化硼（h-BN）异质结构展现出众多独特的物理性质，如量子霍尔效应和奇异的关联态，这在新型电子器件设计中具有广阔的潜在应用前景。了解此类结中的热输运对于控制未来纳米器件的性能和稳定性至关重要。在这项工作中，我们使用非平衡分子动力学模拟，系统地研究了不对称石墨烯/h-BN范德华异质结构中的热输运。研究发现，热量更倾向于从单层区域流向多层区域，从而产生显著的热整流（TR）效应。为了确定热整流的最佳条件，我们研究了样品长度、缺陷密度、不对称程度、环境温度和范德华相互作用强度的影响。特别地，我们发现通过将耦合强度从1增加到10，热整流比可以提高约1个数量级，这明显不同于通常认为的热整流比实际上对相互作用强度不敏感甚至随其降低的观点。详细的光谱分析表明，热整流比的这种意外增加可归因于由于层间耦合增强导致的被包裹石墨烯的声子性质发生了重大改变。我们的结果阐明了范德华相互作用对纳米结构中热传导的重要性。
