IDR: Thermal and Electronic Transport Processes in Monolayer-Scale Chemically Ordered Semiconductor Films

IDR：单层化学有序半导体薄膜中的热和电子传输过程

• 批准号: 1134301
• 负责人: Pamela Norris
• 金额: $ 53.92万
• 依托单位: University of Virginia Main Campus
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-08-15 至 2015-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1134301&HistoricalAwards=false
• 关键词: IDR; Thermal; Electronic; Transport; Processes

PI: Pamela M. Norris and Jerrold FloroCBET-1134301The control of thermal energy (heat) flowing through a material, expressed as the thermal conductivity of the material, is critically important to many applications. A particular technology that is relevant to concerns over energy consumption and global warming is thermoelectric generators, which contain materials that allow the inevitable waste heat generated in any fuel-burning process to be further converted directly to electricity. Good thermoelectric materials (those that produce the most electricity for a given heat load) are semiconductors that must simultaneously have low thermal conductivity and high electrical conductivity. These two requirements are at odds with one another, and this tension has frustrated the development of highly efficient thermoelectric devices.This proposal will investigate a new approach to making better thermoelectric materials. The primary concept is that alloys of Ge and Si will be grown into atomically ordered structures. This ordering takes place spontaneously, producing alternating chemical arrangements of Ge and Si atoms that cannot be formed by conventional synthetic approaches. Ordering should keep the electrical conductivity high, since it reduces the scattering of electrical charges compared to a disordered alloy, and it can reduce the thermal conductivity by exploiting a special kind of scattering mechanism, called Umklapp scattering. Simulations predict that Umklapp scattering will be enhanced by chemical ordering, especially at higher temperatures where thermoelectric generators typically operate. This project employs advanced growth and characterization techniques to produce these materials, ascertain their ordering and measure their transport properties. Molecular dynamics simulations of energy flow in ordered structures will be performed in support of the results. The research will lend new insights into how atomic-scale ordering affects both electrical and thermal conduction.This research will investigate a new materials design strategy for ultimate use in thermoelectric generators. These devices convert waste heat into electricity, but much more efficient thermoelectric materials are needed in order to be cost effective. In addition to thermoelectrics, developing new approaches to controlling thermal conduction in materials is critical to many technologies. An important example is the computer chip, where high-power processors generate tremendous heat that must be efficiently conducted away from the device so that is does not destroy itself. Beyond the technical contributions of this project lies a strong commitment by the investigators to tightly integrate research and education through the experiential and formal training of two graduate students. Additionally, undergraduate students will be recruited from underrepresented groups in engineering. For these students, exposure to the research environment can be career-defining. Both the principal investigators direct and participate in extensive science outreach activities with K-12 schoolchildren and educators. Much of the focus of these effors is on bringing nano to the public, and for this new project a thermoelectric demonstrator module will be developed that will serve as an example of how materials nanostructuring can improve properties important in the drive to reduce fossil fuel consumption.

对流经材料的热能（热）的控制，以材料的导热率来表示，对许多应用都是至关重要的。与能源消耗和全球变暖相关的一种特殊技术是热电发电机，它包含的材料可以将任何燃料燃烧过程中产生的不可避免的废热进一步直接转化为电能。好的热电材料（在给定热负荷下产生最多电的材料）是半导体，它必须同时具有低导热性和高导电性。这两种要求是相互矛盾的，这种矛盾阻碍了高效热电装置的发展。这项提议将研究一种制造更好的热电材料的新方法。主要的概念是，锗和硅合金将生长成原子有序结构。这种排序是自发发生的，产生了常规合成方法无法形成的Ge和Si原子的交替化学排列。有序应该保持高导电性，因为与无序合金相比，有序可以减少电荷的散射，并且可以通过利用一种特殊的散射机制（称为Umklapp散射）来降低导热性。模拟预测，化学排序将增强乌姆克拉普散射，特别是在热电发电机通常工作的较高温度下。该项目采用先进的生长和表征技术来生产这些材料，确定它们的顺序并测量它们的传输特性。分子动力学模拟的能量流在有序结构将进行支持的结果。这项研究将为原子尺度的有序如何影响电传导和热传导提供新的见解。本研究将探讨一种最终用于热电发电机的新材料设计策略。这些装置将废热转化为电能，但为了达到成本效益，还需要更高效的热电材料。除了热电学之外，开发控制材料热传导的新方法对许多技术都至关重要。一个重要的例子是计算机芯片，其中高功率处理器产生巨大的热量，必须有效地从设备中传导出去，以防止其自我破坏。除了这个项目的技术贡献之外，研究人员还坚定地承诺，通过对两名研究生的经验和正式培训，将研究和教育紧密结合起来。此外，本科学生将从工程领域代表性不足的群体中招聘。对于这些学生来说，接触研究环境可以决定他们的职业生涯。两位主要研究人员都指导并参与了与K-12学童和教育工作者一起开展的广泛的科学推广活动。这些努力的重点是将纳米技术带给公众，对于这个新项目，一个热电示范模块将被开发出来，它将作为一个例子，说明纳米材料如何在减少化石燃料消耗的驱动中提高重要的性能。