September 17th 3:00 to 4:30 pm in 442 Dana.
Title: "Aluminum Nitride Piezoelectric Microelectromechanical Resonant Physical Sensors"
Matteo Rinaldi (advisor)
Miniaturized sensors are nowadays found in a wide variety of application, such as smart mobile devices, automotive, healthcare and environmental monitoring. The recent advancements of Micro/Nano-Electro-Mechanical Systems (MEMS/NEMS) technology have a tremendous impact on the sensor miniaturization, power consumption and cost reduction, which allow envisioning a new era of senor fusion in which the data collected from multiple individual sensors are combined to get information about the environment that is more accurate and reliable than the individual sensory data. This trend towards sensor fusion has dramatically increased the demand of new technology platforms, capable of delivering multiple sensing and wireless communication functionalities in a small foot print. In this perspective, the unique capability of Aluminum Nitride (AlN) piezoelectric MEMS/NEMS resonant technology to deliver high performance resonant sensors (i.e. accelerometers and gyroscopes) and radio frequency (RF) components (i.e. filters and oscillators) makes it the best platform for the implementation of the next generation miniaturized, low power, multi-functional and reconfigurable wireless sensing and communication systems.
Among different sensors, miniaturized, low power and high resolution integrated infrared detectors and magnetometers are crucial elements to be included in the next generation wireless sensing and communication systems. In this thesis, the potential of employing AlN piezoelectric MEMS/NEMS resonators for the implementation of two kinds of high performance physical sensors: Infrared (IR) detectors and magnetic field sensors is explored. By taking the unique advantage of the AlN MEMS/NEMS resonant technology, which is a combination of extremely high sensitivity to external perturbations (due to their very reduced dimensions) and ultra-low noise performance (due to the intrinsically high quality factor, Q, of such resonant devices), the first device prototypes based on AlN nano-plate resonators (AlN-NPRs) have been successfully demonstrated for the first time and showed promising performance. The demonstrated IR detector with the best performance so far showed a Noise Equivalent Power (NEP) of ~382 pW/rt-Hz (in a 33 Hz measurement bandwidth), Noise Equivalent Temperature Difference (NETD) of ~411 mK and thermal time constant of 5 ms, closing to the specifications of commercial available products (i.e. micro-bolometers and thermopiles). The proposed magnetic field sensor based on a piezoelectric and magnetostrictive bilayer of AlN/FeGaB showed a detection limit of 16 nT/rt-Hz (in a 10 Hz measurement bandwidth) and angular resolution of 0.34°, proofing its potential for the application of extremely small magnetic field detection and miniaturized electronic compasses for mobile devices.
In this proposal, the preliminary work on the design, fabrication and characterization of the first device prototypes of IR detectors and magnetometers will be discussed. Then, the future work, which will be focusing on the development and optimization of high performance IR/THz detectors, will be proposed. Two major tasks will be proposed for this proposal: first, by taking the advantage of the unique scaling capability of AlN MEMS resonant technology, to scale the AlN-NPRs for the implementation of focal plane arrays (FPAs) for imaging applications; second, to design and integrate metamaterial THz absorber to the AlN-NPRs for the implementation of frequency selective THz detectors for the application of THz spectroscopy.