Thermoelectric metal nanostructures: Disorder, plasmons, and photodetection

摘要：非技术性：热流和电荷流耦合在一起，这些热电效应支撑着各种关键技术，包括恒温器、电动冰箱和光电探测器。热电性能可以通过在纳米尺度上构建材料来实现。使用扫描激光作为可移动的热源，PI的研究小组发现了意想不到的热电效应，即使在名义上简单的金属结构中也是如此。具体地说，晶界和表面化学可以改变热电响应，在电子必须通过金属电极之间纳米级间隙的结构中，极大地增强光伏是可能的。该项目将确认这些令人惊讶的特征背后的机制，并以此为基础创建和表征基于金属光学天线的新型光电探测器的原型。虽然不像基于半导体的光电探测器那样灵敏，但金属光学天线系统在几何上是可调的，具有不同的噪声处理，并且制造起来更简单。结果将通过出版物、在会议上的演讲和PI在他的博客上的流行文章来传播。该项目将为研究生和本科生研究人员提供培训和专业发展，帮助建立下一代技术熟练和创新的劳动力队伍。PI还将通过正在进行的莱斯项目与来自其他机构的K12教师和本科生合作。通过他与《休斯顿纪事报》合作的博客和著作，PI将继续普及纳米级科学和工程，特别是该项目的研究成果。技术：纳米结构热电设备作为技术和工具具有巨大的潜力，可以获得控制和优化纳米级能量流动所需的基本科学和工程知识。通过扫描激光显微镜将电子传输测量和照明相结合，Pi的团队在名义上简单的金属纳米结构中发现了意想不到的光热电效应。金属纳米线在Seebeck响应中表现出以前没有报道过的不均匀，这表明晶界和表面化学可以作为工程热电响应的工具。与非隧穿结构相比，金属电极之间的纳米尺度隧穿间隙显示出极大的光电压增强，其机制是与等离子体增强的热电子隧穿相一致的材料和极化依赖关系。该项目的学术价值在于其三个具体的研究目标：通过控制表面条件(通过自组装单分子膜)和颗粒结构来量化和设计金属纳米结构中的光热电效应；了解和优化纳米GaP中极大地增强的热电效应；以及展示基于这些增强的光热电效应的光电探测器，观察灵敏度和噪声特性。PI的研究生和本科生团队将与理论家合作，对这些结构中工作的光电和热传输过程进行建模，为优化响应提供关键反馈。结果将通过出版物、在会议上的陈述以及在适当的情况下通过国际和平协会的博客广泛传播。该项目将为研究生和本科生研究人员提供培训和专业发展，帮助建立下一代技术熟练和创新的劳动力队伍。PI还将通过正在进行的莱斯项目与来自其他机构的K12教师和本科生合作。通过他与《休斯顿纪事报》合作的博客和文章，PI将继续普及纳米科学和工程，特别是这个项目的研究成果。

Abstract:Nontechnical:The flow of heat and electric charge are coupled together, and these thermoelectric effects underpin diverse critical technologies, including thermostats, electrically driven refrigerators, and photodetectors. Thermoelectric properties can be engineered by structuring materials on the nanoscale. Using a scanning laser as a moveable heat source, the PI's group has revealed unexpected thermoelectric effects even in nominally simple metal structures. Specifically, grain boundaries and surface chemistry can modify thermoelectric response, and greatly enhanced photo-voltages are possible in structures where electrons have to "tunnel" across a nanoscale gap between metal electrodes. This project will confirm the mechanisms behind these surprising features, and build upon this knowledge to create and characterize prototypes of new photodetectors based on metal optical antennas. While not as sensitive as semiconductor-based photodetectors, metal optical antenna systems are geometrically tunable, have different noise processes, and can be simpler to fabricate. Results will be disseminated via publications, presentations at conferences, and popular writings by the PI on his blog. This project will provide training and professional development to graduate students and undergraduate researchers, aiding in the creation of the next generation of a technologically skilled and innovative workforce. The PI will also work with K12 teachers and undergraduates from other institutions through ongoing Rice programs. Through his blog and writings in collaboration with the Houston Chronicle, the PI will continue to popularize nanoscale science and engineering in general, and this project's research outcomes in particular.Technical:Nanostructured thermoelectric devices have enormous potential as technologies and as tools to acquire the basic scientific and engineering knowledge necessary to control and optimize the flow of energy at the nanoscale. By coupling electronic transport measurements and illumination via a scanning laser microscope, the PI's group has found unexpected photothermoelectric effects in nominally simple metal nanostructures. Metal nanowires demonstrate previously unreported inhomogeneities in Seebeck response, indicating that grain boundaries and surface chemistry can be tools for engineering thermoelectric response. Nanoscale tunneling gaps between metallic electrodes show greatly enhanced photovoltages compared to nontunneling structures, with material and polarization dependences that are consistent with plasmon-enhanced hot electron tunneling as the mechanism. The intellectual merit of this project lies in its three specific research goals: quantifying and engineering photothermoelectric effects in metal nanostructures through control of surface conditions (via self-assembled monolayers) and grain structure; understanding and optimizing greatly enhanced thermoelectric effects in nanogaps; and demonstrating photodetectors based on these enhanced photothermoelectric effects, looking at sensitivity and noise properties. The PI's team of graduate and undergraduate students will collaborate with theorists in modeling the optoelectronic and thermal transport processes at work in these structures, providing critical feedback for optimization of response. Results will be disseminated broadly through publications, presentations at conferences, and when appropriate the PI's blog. This project will provide training and professional development to graduate students and undergraduate researchers, aiding in the creation of the next generation of a technologically skilled and innovative workforce. The PI will also work with K12 teachers and undergraduates from other institutions through ongoing Rice programs. Through his blog and writings in collaboration with the Houston Chronicle, the PI will continue to popularize nanoscale science and engineering in general, and this project's research outcomes in particular.