Resonant Infrared Sensors Using Pyroelectric and Piezoelectric Effects

Regents Of The University Of Michigan - Ann Arbor, Ann Arbor MI

Investigators

Abstract

Resonant Infrared Sensors Using Pyroelectric and Piezoelectric Effects PROJECT SUMMARY This 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.