Li Keqiang, Cheng Yajuan, Dou Maofeng, Zeng Wang, Volz Sebastian, Xiong Shiyun
Guangzhou Key Laboratory of Low-Dimensional Materials and Energy Storage Devices, School of Materials and Energy, Guangdong University of Technology, Guangzhou 510006, China.
Institute of Functional Nano and Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Soochow University, 199 Ren'ai Road, Suzhou 215123, China.
Nanomaterials (Basel). 2021 Dec 30;12(1):123. doi: 10.3390/nano12010123.
Understanding the thermal transport in nanostructures has important applications in fields such as thermoelectric energy conversion, novel computing and heat dissipation. Using non-homogeneous equilibrium molecular dynamic simulations, we studied the thermal transport in pristine and resonant Si membranes bounded with {110} facets. The break of symmetry by surfaces led to the anisotropic thermal transport with the thermal conductivity along the [110]-direction to be 1.78 times larger than that along the [100]-direction in the pristine structure. In the pristine membranes, the mean free path of phonons along both the [100]- and [110]-directions could reach up to ∼100 µm. Such modes with ultra-long MFP could be effectively hindered by surface resonant pillars. As a result, the thermal conductivity was significantly reduced in resonant structures, with 87.0% and 80.8% reductions along the [110]- and [100]-directions, respectively. The thermal transport anisotropy was also reduced, with the ratio κ110/κ100 decreasing to 1.23. For both the pristine and resonant membranes, the thermal transport was mainly conducted by the in-plane modes. The current work could provide further insights in understanding the thermal transport in thin membranes and resonant structures.
了解纳米结构中的热输运在热电能量转换、新型计算和散热等领域具有重要应用。通过非均匀平衡分子动力学模拟，我们研究了由{110}面界定的原始和共振硅膜中的热输运。表面引起的对称性破缺导致了各向异性热输运，在原始结构中，沿[110]方向的热导率比沿[100]方向的热导率大1.78倍。在原始膜中，声子沿[100]和[110]方向的平均自由程可达~100 µm。这种具有超长平均自由程的模式会受到表面共振柱的有效阻碍。结果，共振结构中的热导率显著降低，沿[110]和[100]方向分别降低了87.0%和80.8%。热输运各向异性也降低了，κ110/κ100的比值降至1.23。对于原始膜和共振膜，热输运主要由面内模式进行。当前的工作可以为理解薄膜和共振结构中的热输运提供进一步的见解。
