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

点击翻译按钮获取中文摘要

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.