Nanoscale and microscale effects and electromechanical aspects for design of thin films and sensors

The present research involves nanoscale and microscale effects and the associated electromechanical aspects for design of thin films and sensors. Two principal areas are presented here. First PZT thin films, and second carbon nanotubes.; In this thesis, first, the dynamical characteristics of a PZT thin film microsensor are studied. As a benchmark for validating the overall developments, a bridge structure PZT thin film microtransducer with mass loading for sensing and actuation that was previously fabricated using bulk machining of microelectromechanical systems (MEMS) and special techniques for deposition of PZT thin film on silicon wafer is employed. Potential applications of bridge structure PZT thin film microtransducer for sensing and actuation are pointed out. Dynamic studies of PZT thin film microsensors are also reviewed. The contributions include the following developments: (A) Motion equation of the PZT thin film microsensor due to mechanical thermal noise is established with consideration of boundary conditions and geometry of the sensor. (B) To optimize and evaluate the design, a bridge structure with proof mass is modeled in which the Young's modulus of the thin film is simulated using molecular dynamics, and the mechanical properties and Brownian thermal noise equivalent acceleration due to mechanical thermal noise are evaluated using the motion equation mentioned above. (C) A bridge structure PZT thin film microtransducer with mass loading that was designed and fabricated previously using MEMS will be used to benchmark the developments. To verify the micro-transducer, impedance of PZT thin film built in the bridge was measured in the typical range of frequency. For potential use in applications such as accelerometer, this microtransducer was calibrated using a shaker with a commercial accelerometer. (D) Theoretical analysis against measurement results are made to improve future designs. (E) Last, conclusions and expected contribution are summarized and recommendations for future work are addressed.; In the second phase, the concept of a curved lattice and its reciprocal lattice in curvilinear coordinate system are introduced to study the energy band of single-walled carbon nanotubes wrapped at a helical angle. (Abstract shortened by UMI.)...