Thermoelectric-Plasmonic Hybrid Infrared Sensor for Uncooled Multispectral Application

摘要非技术性：光电探测器是现代传感和成像技术的核心。光电探测器的一个非常著名的应用是数码相机的成像传感器。与现有的可见光光电探测方法相比，在室温下对高灵敏度的近红外和中红外光的传感仍然具有挑战性。先进的红外线光电探测器需要将设备冷却到零下100摄氏度以下。红外光热电信号的转换是检测红外光的一种有效方法。然而，这种方法(称为热电效应)有几个固有的问题，这些问题阻碍了设备的小型化，并限制了分辨不同波长的红外光的能力。此外，现有的热电材料在室温下将光能转换为电能的效率很低。仅通过改进设备的一个方面来解决当前技术的弱点是困难的。在这个项目中，将在新材料设计、理论性能评估和新型电子器件制造方面进行多学科研究。该项目的光电探测器将在室温下高效采集不同波长的红外光。多学科研究的性质将有利于将技术研究与教育和外联相结合。该项目的基础科学、技术和原型产品将用于匹兹堡初级科学院(PJAS)的纳米技术工作坊和匹兹堡当地高中生的科学研究课程。此外，PI和共同PI将把项目成果纳入匹兹堡大学材料科学、机械工程和电气工程专业的本科生和研究生课程。技术：这项研究的目标是开发一种热电红外传感器，具有多光谱分辨率，无需低温制冷。这将使用二维材料的混合结构来实现，例如石墨烯和硫化钼，以及等离子金属纳米壳。拟议结构的基本假设如下。首先，与传统的块状热电材料不同，石墨烯和钼纳米片具有极大的表面积与体积比。这一特征可以提供通过修改或掺杂表面来提高塞贝克系数的机会。第二，特征波长可调的介电核-金属纳米壳颗粒的表面等离激元可以实现对红外光的高吸收和波长依赖性。第三，具有低热容和低导热系数的氮化硅薄膜可以使红外吸收的局部温度有更快更大的提高。这将改善红外传感器的动态响应和信噪比。氮化硅的低导热系数可以通过增加结构和质量无序进一步降低。这项研究的主要学术价值在于对纳米尺度的热和电荷输运性质有了基本的了解。通过模拟和实验相结合的研究，主要研究人员将开发一个模型来预测自由支撑膜的物理性质(如塞贝克系数、导热系数和热容)如何影响热电红外传感器的重要性能因素，如输出信号、响应时间和信噪比。此外，金属纳米壳层对光的选择性吸收增强和随后的能量耗散将为解决入射红外光的波长和通过局部加热产生温度梯度提供一种新的途径。

AbstractNontechnical: A photodetector is at the heart of modern sensing and imaging technology. A very well-known application of photodetectors is an imaging sensor of a digital camera. Compared with the well-established photo-detection methods of visible light, the sensing of near- and mid-infrared light with high sensitivity at room temperature is still challenging. An advanced infrared light photodetector requires cooling of the device below -100oC. Conversion of infrared light-heat-electric signal is a useful way to detect IR light. However, this approach (called as a thermoelectric effect) has several inherent problems which prevent a miniaturization of the device and limit an ability to resolve infrared light with different wavelengths. Also, existing thermoelectric materials exhibit a low efficiency in converting light energy to electric energy at room temperature. It is difficult to address weaknesses of current technology by improving only a single aspect of devices. In this project, multidisciplinary research will be performed for new materials design, theoretical performance evaluation and novel electric device fabrication. The photodetector from this project will efficiently collect infrared light of different wavelengths at room temperature. The nature of the multidisciplinary research will be beneficial in integrating the technical research with education and outreach. Basic science, technology and prototype product of the project will be used in "Nanotechnology" workshop for the Pittsburgh Junior Academy of Science (PJAS) and "Science Research" course for Pittsburgh local high school students. In addition, The PI and co-PIs will integrate outcomes of the project into undergraduate and graduate courses in materials science, mechanical engineering and electrical engineering programs at the University of Pittsburgh. Technical:The objective of this research is to develop a thermoelectric infrared sensor that has a multispectral resolution capability and operates without cryogenic cooling. This will be accomplished using hybrid structures of 2-dimensional materials, such as graphene and molybdenum sulfide, and plasmonic metal Nano-shells. The hypotheses underlying the proposed structure are as follows. First, unlike conventional bulk thermoelectric materials, graphene and molybdenum Nano sheets have an extremely large surface area to volume ratio. This feature can provide an opportunity to improve the Seebeck coefficient through modifying or doping the surface. Second, high and wavelength-dependent absorption of infrared light can be enabled by the surface plasmons of dielectric core - metal Nano-shell particles with tunable characteristic wavelengths. Third, a thin free-standing silicon nitride membrane with low heat capacity and low thermal conductivity can allow faster and larger increase of local temperature upon IR light absorption. This will improve dynamic response and the signal-to-noise ratio of an IR sensor. The low thermal conductivity of silicon nitride can be further reduced by increasing structural and mass disorder. The major intellectual merit of the proposed research lies in the fundamental understanding of the heat and charge transport properties at nanoscale. Through integrated research of simulation and experiment, the principal investigators will develop a model to predict how physical properties (e.g. Seebeck coefficient, thermal conductivity and heat capacity) of a free standing membrane affect important performance factors of the thermoelectric IR sensor, such as output signal, response time and signal-to-noise ratio. Moreover, enhancement of selective light absorption by the metal Nano-shells and subsequent energy dissipation will show a novel way to resolve the wavelength of incident infrared light and create a temperature gradient through local heating.