Resonant Infrared Sensors Using Pyroelectric and Piezoelectric Effects

使用热释电和压电晶体的谐振红外传感器项目概述该提案解决了红外（IR）检测和成像领域的关键需求，并提出了一种新的方法来感测超高精度的IR辐射。近年来，人们对高精度红外探测器的兴趣越来越大，其应用范围从军事和安全到汽车和消费市场。理想的红外探测器需要灵活，非制冷，并表现出超高的灵敏度。在所提出的传感器中，压电和热电效应将在单个谐振传感器元件中被利用，以实现5 mK的噪声等效Δ温度。这样的性能使得可以用本文提出的低成本非冷却系统代替低温冷却的光子检测器。由于压电和热释电效应的同时使用，建议的红外探测器的灵敏度与面积无关。谐振效应的使用增加了信噪比，并且消除了对热释电检测器所需的机械斩波器的需要，进一步减小了系统的整体尺寸。可以设想这些低噪声非制冷红外探测器在指纹传感器、夜视、手持成像和接近传感器中的应用。 本研究的创新点包括：（1）以氮化镓为结构材料，将压电性与热释电性结合在单一的感测元件中，以实现非致冷红外探测器，其灵敏度可与光子探测器相媲美;（2）使用共振感测器阵列与参考共振器，以提高信噪比;（3）采用选择性区域外延生长的低应力、高极化的GaN材料，（4）采用碳纳米管-聚合物纳米复合材料薄膜作为吸收层，提高了材料的红外灵敏度，其红外吸收率为0.99;（5）二维电气体（2DEG）作为无金属电极的探索：该研究克服了热探测器面积大、响应时间慢、灵敏度相对较低的缺点。在单个谐振元件中同时使用压电和热释电效应，导致灵敏度和响应时间提高4.5倍。除了红外探测，所提出的微系统传感器阵列能够感测，超低功耗，多个被测对象，即磁场，惯性，和气体光谱。因此，所提出的平台技术使多传感器融合的实施成为可能。GaN的独特性质，如高电子迁移率和大的压电和热释电系数，使其有可能实现高信噪比和低功耗。此外，GaN的高化学稳定性和2DEG承受高温和低温的能力可以导致广泛的应用。 除了在传感系统中的应用外，高Q GaN谐振器还有望在与新兴高性能GaN电子产品集成的频率合成器和高性能滤波器中具有深远的应用。因此，该平台具有很大的潜力，是MEMS社区的极大兴趣。更广泛的影响：提出的高性能和小尺寸的谐振传感器可以在不同的领域，如环境传感器，生物医学传感器，智能传感器和传感器网络的广泛应用。除了概述的研究工作，将建立一个综合教育计划，旨在通过直接参与研究活动来教育和激励学生。微机电谐振微系统的研究对学生来说特别有价值，因为它涵盖了各种主题，包括微纳米纤维，材料表征，结构分析，损耗机制物理学，热和辐射效应，建模和高频接口电子学。 因此，它在基础工程科学中具有前所未有的多学科教育价值。教育计划的目标是通过以下方式教育和激励学生：（1）为学生创造一个多学科的科学学习环境，并直接培训两名博士生，（2）夏季教育推广计划，使几名高中生接触MEMS领域，并通过直接参与拟议的研究活动来促进微系统，（3）弱势群体的本科生参与研究所的研究和教育活动。

Resonant Infrared Sensors Using Pyroelectric and Piezoelectric EffectsPROJECT SUMMARYThis proposal addresses critical needs in the field of infrared (IR) detection and imaging and proposes a new approach to sense the IR radiation with ultra-high precision. In recent years, there has been a growing interest in high-precision IR detectors for application ranging from military and security to automotive and consumer market. Ideal IR detectors need to be agile, un-cooled, and exhibit ultra-high sensitivity. In the proposed sensor, both piezoelectric and pyroelectric effects will be exploited in a single resonant sensor element to achieve noise equivalent delta temperature of 5mK. Such performance makes it possible to replace cryogenically cooled photonic detectors with the low-cost uncooled system proposed herein. The sensitivity of the proposed IR detector is independent of area thanks to the simultaneous employment of piezo and pyroelectric effect. The use of the resonant effect increases the signal to noise ratio and eliminates the need for mechanical choppers that are needed for pyroelectric detectors, further reducing the overall size of the system. Applications of these low-noise un-cooled IR detectors in fingerprint sensors, night vision, hand-held imaging, and proximity sensors can be envisaged. The novelties of the proposed research include: (1) The combination of piezoelectricity and pyroelectricity in a single sensor element using GaN as the structural material to implement an un-cooled IR detector with sensitivity comparable to that of photonic detectors;(2) The use of resonant sensor array and a reference resonator to improve signal to noise ratio; (3) The employment of low-stress and highly polarized GaN grown using selective area epitaxy; (4) The application of thin film CNT-polymer nanocomposites with IR absorptivity 0.99 as the absorbing layer for improved IR sensitivity; (5) The exploration into the use of two-dimensional electric gas (2DEG) as a metal-less electrode.Intellectual merit: This research eliminates the disadvantages of thermal detectors, namely large area, slow response time and relatively small sensitivity. Simultaneous employment of piezo and pyroelectric effect in single resonant element leads to 4.5× improvement in sensitivity and response time. In addition to infrared detection, the proposed microsystem sensor array is capable of sensing, with ultra-low power, multiple measurands, namely magnetic field, inertial, and gas spectra. Therefore, the proposed platform technology makes the implementation of multi-sensor fusion possible. Unique properties of GaN, such as high electron mobility and large piezo and pyroelectric coefficient make it possible to achieve a high signal to noise ratio and low power consumption. Furthermore, the high chemical stability of GaN and the ability of the 2DEG to withstand high and low temperatures can lead to a broad range of applications. In addition to their application in sensing systems, high-Q GaN resonators are envisioned to have farreaching applications in frequency synthesizers and high-performance filters integrated with emerging high-performance GaN electronics. Therefore, the proposed platform has a great potential and is of great interest to the MEMS community.Broader Impact: The proposed high-performance and small-size resonant sensors could have broad applications in diverse areas such as environmental sensors, biomedical sensors, intelligent sensors, and sensor networks. In addition to the outlined research effort, an integrated educational program will be established which aims to educate and motivate students through direct participation in the research activities. The study of microelectromechanical resonant microsystems is of particular value for students as it encompasses a variety of topics ranging from micro and nanofabrication, material characterization, structural analysis, physics of loss mechanisms, thermal and radiation effects, modeling and high frequency interface electronics. Therefore, it has an unprecedented multidisciplinary educational value at the fundamental engineering science. The goal of the educational plan is to educate and motivate students by (1) creating a multi-disciplinary scientific learning environment for students and directly training two doctoral students,(2) summer educational outreach program to expose several high school students to the field of MEMS, and microsystems by involving them directly in the proposed research activities, and (3) Involvement of undergraduate students from underrepresented groups in PIs' research and educational activities.