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Microforce Sensors Based On Microcantilevers With Two Piezoelectric PZT Thin-Film Elements

Posted on:2007-09-10Degree:DoctorType:Dissertation
Country:ChinaCandidate:M W LiuFull Text:PDF
GTID:1118360185473234Subject:Mechanical and electrical engineering
Abstract/Summary:PDF Full Text Request
The study of microelectromechanical systems (MEMS) has shown significant opportunities for microsensors and microactuators based on piezoelectric PZT films and silicon micromachining technology. The piezoelectric microforce sensors offer a lot of advantages for MEMS applications such as low power dissipation, high sensitivity, and easily integrated with piezoelectric microactuators. In spite of many advantages above, the research efforts are relatively limited compared to piezoresistive microforce sensors. In this thesis, in order to increase the sensitivity of the piezoelectric microforce sensors, and integrate with the piezoelectric microactuators, PZT thin-film microfroce sensors are systematically studied in terms of the deposition and characterization of the PZT thin films, design, fabrication and testing of the microforce sensors based on microcantilever structures.Ferroelectric lead zirconate titanate (PZT) thin films are deposited by sol-gel method on Pt/Ti/SiO2/Si substrates. The effects of deposited process and film thickness on the microstructures, crystalline phases and electrical properties of the PZT films are investigated. A novel method is presented to control the crystallographic orientation of the PZT thin films by modifying the coating layers in one annealing cycle of the sol-gel process. The film quality and electrical properties of the PZT films increase with the decreasing of film thickness in one annealing cycle. The critical thickness is increased, and better ferroelectric properties are obtained. The influence of the spontaneous polarization on the piezoelectric properties of ferroelectric films is investigated. Based on the converse piezoelectric effect, longitudinal piezoelectric coefficients d33 of PZT thin films are measured using the optimized atomic force microscopy (AFM) method. The PZT films demonstrate good piezoelectric properties that increase with the film thickness.Device structures of the piezoelectric microforce sensors are designed. Different from the conventional piezoelectric microcantilevers with a piezoelectric film sandwiched between two metal electrodes on cantilever structures, two novel piezoelectric microcantilever structures with two piezoelectric elements, including bimorph and two-segment PZT films, are designed. The bimorph piezoelectric microcantilevers will improve the sensing performance of microforce sensors, compared to unimorph piezoelectric microcantilevers. As a versatile device integrating the sensing and actuating functions, the two piezoelectric elements of the bimorph or two-segment piezoelectric cantilevers can be used for the sensing and actuation elements, respectively. The coupling problem induced by one piezoelectric...
Keywords/Search Tags:MEMS, PZT Film, Two Piezoelectric Thin-film Elements, Microcantilever, Microforce Sensor
PDF Full Text Request
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