Artie McFerrin Department of Chemical Engineering, Texas A&M University, College Station, TX 77845-3122, USA.
Nanotechnology. 2011 Apr 15;22(15):155701. doi: 10.1088/0957-4484/22/15/155701. Epub 2011 Mar 10.
Quantum dot superlattices (QDSLs) have been proposed for thermoelectric applications as a means of increasing thermal conductivity, σ, and reducing the lattice thermal conductivity, κ(l), to increase the dimensionless thermoelectric figure of merit, ZT. To fully exploit the thermoelectric potential of Si-Ge quantum dot superlattices (QDSLs), we performed a thorough study of the structural interplay of QDSLs with κ(l) using Green-Kubo theory and molecular dynamics. It was found that the resulting κ(l) has less dependence on the arrangement of the dots than to dot size and spacing. In fact, regardless of arrangement or concentration, QDSLs show a minimum κ(l) at a dot diameter of 1.4-1.6 nm and can reach values as low as 0.8-1.0 W mK⁻¹, increasing ZT by orders of magnitude over bulk Si and Ge. The drastic reduction of thermal conductivity in such a crystalline system is shown to be the result of both the stress caused by the dots as well as the quality of the Si-Ge interface.
量子点超晶格（QDSL）已被提议用于热电应用，作为增加热导率σ和降低晶格热导率κ(l)的一种手段，以提高无量纲热电优值ZT。为了充分利用 Si-Ge 量子点超晶格（QDSL）的热电潜力，我们使用格林-库珀理论和分子动力学对 QDSL 与 κ(l) 的结构相互作用进行了全面研究。结果表明，所得的 κ(l)对点的排列的依赖性小于对点的大小和间距的依赖性。事实上，无论排列方式或浓度如何，QDSL 在直径为 1.4-1.6nm 的点处表现出最低的 κ(l)，并且可以达到低至 0.8-1.0WmK⁻¹的水平，ZT 比体 Si 和 Ge 高出几个数量级。这种晶体系统中热导率的急剧降低被证明是由点引起的应力以及 Si-Ge 界面的质量共同作用的结果。
