Thermal Rectification in Asymmetric Graphene/Hexagonal Boron Nitride van der Waals Heterostructures
Thermal Rectification in Asymmetric Graphene/Hexagonal Boron Nitride van der Waals Heterostructures
复制标题
不对称石墨烯/六方氮化硼范德华异质结构中的热整流
DOI：
10.1021/acsami.9b22498
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发表时间：
2020
影响因子：
9.5
通讯作者：
Chen Ke-Qiu
中科院分区：
文献类型：
--
作者：
Chen Xue-Kun;Pang Min;Chen Tong;Du Dan;Chen Ke-Qiu
通过范德华相互作用组装的石墨烯/六方氮化硼（h-BN）异质结构显示出许多独特的物理性质，如量子霍尔效应和奇异相关态，在新型电子器件的设计中具有广阔的应用前景。了解这种结中的热传递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 vdW异质结构中的热传递。发现热量更倾向于从单层流向多层区域，导致显著的热整流（TR）效应。研究了样品长度、缺陷密度、不对称程度、环境温度和vdW相互作用强度对TR的影响。特别是，我们发现通过将耦合强度从1增加到10，TR比可以提高约1个数量级，这与通常认为TR比实际上不敏感甚至随相互作用强度而降低的观点明显不同。详细的光谱分析表明，这种意想不到的TR比增加可归因于由于层间耦合增强而严重改变了包裹石墨烯的声子特性。我们的研究结果阐明了vdW相互作用对纳米结构热传导的重要性。
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.