Determining absolute Seebeck coefficients from relative thermopower measurements of thin films and nanostructures
Determining absolute Seebeck coefficients from relative thermopower measurements of thin films and nanostructures
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DOI：
10.1063/1.5143447
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发表时间：
2020-02-24
影响因子：
3.2
通讯作者：
Zink, B. L.
中科院分区：
文献类型：
--
作者：
Mason, S. J.;Hojem, A.;Zink, B. L.
热电效应的测量，例如塞贝克效应，即响应所施加的热梯度而产生的电场，对于受热的纳米级器件中使用的一系列薄膜和纳米结构非常重要。在许多情况下，要清楚地了解这些设备的基本物理原理，需要了解材料的固有热电特性，而不是直接来自测量且始终包括电压引线贡献的所谓“相对”量。然而，对于薄膜或纳米结构，确定绝对塞贝克系数 alpha abs 具有挑战性。在这里，我们首先概述了测量 α 绝对值的挑战，然后提出了一种通过微机械热隔离平台在 77 至 350K 温度下进行的相对测量来确定薄膜 α 绝对值的方法。这依赖于相对简单的理论描述，该理论描述基于薄膜样品的莫特关系作为厚度的函数。我们针对一系列金属薄膜演示了这种技术，结果表明 α 绝对值几乎永远不会符合表中体积值的预期，并且对于某些金属（尤其是黄金），甚至 α 绝对值的符号也可以颠倒。我们还评论了声子和磁振子阻力对某些金属薄膜的作用。由 AIP Publishing 许可发布。
Measurements of thermoelectric effects such as the Seebeck effect, the generation of electric field in response to an applied thermal gradient, are important for a range of thin films and nanostructures used in nanoscale devices subject to heating. In many cases, a clear understanding of the fundamental physics of these devices requires knowledge of the intrinsic thermoelectric properties of the material, rather than the so-called "relative" quantity that comes directly from measurements and always includes contributions from the voltage leads. However, for a thin film or nanostructure, determining the absolute Seebeck coefficient, alpha abs, is challenging. Here, we first overview the challenges for measuring alpha abs and then present an approach for determining alpha abs for thin films from relative measurements made with a micromachined thermal isolation platform at temperatures between 77 and 350K. This relies on a relatively simple theoretical description based on the Mott relation for a thin film sample as a function of thickness. We demonstrate this technique for a range of metal thin films, which show that alpha abs almost never matches expectations from tabulated bulk values, and that for some metals (most notably gold) even the sign of alpha abs can be reversed. We also comment on the role of phonon and magnon drag for some metal films. Published under license by AIP Publishing.