School of Engineering, University of Warwick, Coventry CV4 7AL, UK.
Molecules. 2020 Nov 16;25(22):5350. doi: 10.3390/molecules25225350.
In this work we theoretically explore the effect of dimensionality on the thermoelectric power factor of indium arsenide (InA) nanowires by coupling atomistic tight-binding calculations to the Linearized Boltzmann transport formalism. We consider nanowires with diameters from 40 nm (bulk-like) down to 3 nm close to one-dimensional (1D), which allows for the proper exploration of the power factor within a unified large-scale atomistic description across a large diameter range. We find that as the diameter of the nanowires is reduced below < 10 nm, the Seebeck coefficient increases substantially, as a consequence of strong subband quantization. Under phonon-limited scattering conditions, a considerable improvement of ~6× in the power factor is observed around = 10 nm. The introduction of surface roughness scattering in the calculation reduces this power factor improvement to ~2×. As the diameter is decreased to = 3 nm, the power factor is diminished. Our results show that, although low effective mass materials such as InAs can reach low-dimensional behavior at larger diameters and demonstrate significant thermoelectric power factor improvements, surface roughness is also stronger at larger diameters, which takes most of the anticipated power factor advantages away. However, the power factor improvement that can be observed around = 10 nm could prove to be beneficial as both the Lorenz number and the phonon thermal conductivity are reduced at that diameter. Thus, this work, by using large-scale full-band simulations that span the corresponding length scales, clarifies properly the reasons behind power factor improvements (or degradations) in low-dimensional materials. The elaborate computational method presented can serve as a platform to develop similar schemes for two-dimensional (2D) and three-dimensional (3D) material electronic structures.
在这项工作中，我们通过将原子紧束缚计算与线性化玻尔兹曼输运公式相结合，从理论上探讨了维度对砷化铟（InA）纳米线热电功率因子的影响。我们考虑了直径从 40nm（类似体材料）到 3nm（接近一维）的纳米线，这允许在一个大直径范围内通过统一的大规模原子描述来正确地探索功率因子。我们发现，随着纳米线直径减小到 <10nm，塞贝克系数显著增加，这是由于子带量子化作用很强。在声子限制散射条件下，在 = 10nm 左右观察到功率因子有相当大的提高（~6×）。在计算中引入表面粗糙度散射会将这种功率因子提高降低到 ~2×。当直径减小到 = 3nm 时，功率因子减小。我们的结果表明，尽管像 InAs 这样的低有效质量材料在较大直径时可以达到低维行为并展示出显著的热电功率因子改进，但表面粗糙度在较大直径时也更强，这使得大部分预期的功率因子优势都丧失了。然而，在 = 10nm 左右可以观察到的功率因子提高可能是有益的，因为在那个直径处洛伦兹数和声子热导率都降低了。因此，这项工作通过使用跨越相应长度尺度的大规模全带模拟，正确地阐明了低维材料中功率因子改进（或退化）的原因。所提出的精细计算方法可以作为一个平台，为二维（2D）和三维（3D）材料电子结构开发类似的方案。
