Thermoelectric properties of individual bismuth compound nanowires and arrays, and their reliability: towards nanowire-based microstructured thermoelectric devices

我们的项目旨在研究铋化合物纳米线(Bi，Sb，Bi1-xSbx，Bi2Te3，(Bi1-xSbx)2Te3和阵列)的热电优值系数ZT和可靠性，以及它们在纳米线热电模块中的集成。在纳米多孔模板中生长的纳米线是研究低维效应的良好系统，旨在实现热电器件的小型化和改进化。虽然在铋化合物纳米颗粒或多层材料中ZT的增加主要归因于由于额外的声子散射导致AV-BVI固溶体中热导率的降低，但理论预测表明，对于直径小于100 nm的纳米线，ZT的增加既是由于量子尺寸效应导致的功率因数的增加，也是由于额外的表面声子散射导致热导率的降低。在这个项目中，我们将制造直径为10纳米的光滑和粗糙的铋化合物纳米线的大阵列。在第一个SPP阶段专门开发的微芯片将被用来测量单个纳米线的热电优值，作为线材直径、成分、结晶度和表面粗糙度的函数。制备参数将被优化，以最大化p型和n型纳米材料的ZT。铋化合物纳米线的载流子类型、载流子浓度和迁移率将由纳米线场效应晶体管器件的传输特性决定。我们还将研究纳米线阵列的热电性能，这与它们在用于低功率发电和/或制冷以及传感器的新型热电设备中的实施相关。我们的目标是开发一种基于微结构聚合物模板中连续沉积p型和n型纳米线的NW红外传感器原型。将详细研究热电单根纳米线和纳米线阵列的可靠性，重点研究纳米结构和触头在工作条件和热应力下的化学和热稳定性，并找到最合适的技术解决方案。基于在热导率研究方面的具体经验，我们为所有关注纳米结构薄膜中热传输机制的SPP研究小组提供了一个平台，用于测量薄膜的面内热导率。

Our project aims at investigating the thermoelectric figure of merit ZT and the reliability of bismuth compound nanowires (Bi, Sb, Bi1-xSbx, Bi2Te3, and (Bi1-xSbx)2Te3 and arrays, and at their integration in nanowire-based thermoelectric modules. Intending to miniaturize and improve thermoelectric devices, nanowires grown in nanoporous templates are excellent systems to study the effects of low dimensionality. While an increase of ZT in bismuth compound nanograined or multilayer materials has been attributed mainly to a decrease of thermal conductivity in AV-BVI solid solutions due to additional phonon scattering, theoretical predictions propose an enhancement of ZT for nanowires with diameters below 100 nm caused by both an increase in power factor due to quantum-size effects and reduced thermal conductivity due to additional surface phonon scattering. Within this project we will fabricate large arrays of smooth and rough bismuth compound nanowires with diameters < 10 nm. Microchips specifically developed during the first SPP period, will be used to measure the thermoelectric figure of merit of single nanowires as a function of wire diameter, composition, crystallinity, and surface roughness. The fabrication parameters will be optimized to maximize the ZT of both p- and n-type nanomaterials. Carrier type, carrier concentration, and mobility in bismuth compound nanowires will be determined from the transfer characteristics of nanowire field-effect transistor devices. We will also investigate the thermoelectric properties of nanowire arrays, relevant for their implementation in novel thermoelectric devices to be used for low-power generation and/or refrigeration, and sensoric. We aim at developing a NW IR sensor prototype based on the sequential deposition of p- and n-type nanowires in microstructured polymer templates. The reliability of thermoelectrical single nanowires and nanowire arrays will be studied in detail, with specific emphasis in investigating the chemical and thermal stability of both nanostructure and contacts under working conditions and thermal stress, and to find most suitable technological solutions. Based on specific experience in thermal conductivity investigations we offer a platform for in-plane thermal conductivity measurements of thin films for all SPP research groups which are concerned with thermal transport mechanisms in nanostructured thin films.