Samvedi Vikas, Tomar Vikas
School of Aeronautics and Astronautics, Purdue University, West Lafayette, IN 47907, USA.
Nanotechnology. 2009 Sep 9;20(36):365701. doi: 10.1088/0957-4484/20/36/365701. Epub 2009 Aug 18.
Nanoscale engineered materials with tailored thermal properties are desirable for applications such as highly efficient thermoelectric, microelectronic and optoelectronic devices. It has been shown earlier that by judiciously varying the interface thermal boundary resistance (TBR), thermal conductivity in nanostructures can be controlled. In the presented investigation, the role of TBR in controlling thermal conductivity at the nanoscale is analyzed by performing non-equilibrium molecular dynamics (NEMD) simulations to calculate thermal conductivity of a range of Si-Ge multilayered structures with 1-3 periods, and with four different layer thicknesses. The analyses are performed at three different temperatures (400, 600 and 800 K). As expected, the thermal conductivity of all layered structures increases with the increase in the number of periods as well as with the increase in the monolayer thickness. Invariably, we find that the TBR offered by the interface nearest to the hot reservoir is the highest. This effect is in contrast to the usual notion that each interface contributes equally to the heat transfer resistance in a layered structure. Findings also suggest that for high period structures the average TBR offered by the interfaces is not equal. Findings are used to derive an analytical expression that describes period-length-dependent thermal conductivity of multilayered structures.
具有定制热性能的纳米级工程材料对于高效热电、微电子和光电器件等应用来说是很理想的。早前已经表明，通过明智地改变界面热边界电阻（TBR），可以控制纳米结构中的热导率。在本研究中，通过进行非平衡分子动力学（NEMD）模拟来分析TBR在纳米尺度控制热导率方面的作用，以计算一系列具有1 - 3个周期、四种不同层厚度的Si - Ge多层结构的热导率。分析在三个不同温度（400、600和800 K）下进行。正如预期的那样，所有层状结构的热导率随着周期数的增加以及单层厚度的增加而增加。我们始终发现，最靠近热库的界面所提供的TBR最高。这种效应与通常认为在层状结构中每个界面在热传递阻力中贡献相等的观念相反。研究结果还表明，对于高周期结构，界面提供的平均TBR并不相等。研究结果被用于推导一个描述多层结构中与周期长度相关的热导率的解析表达式。
