Thesis
Optimization of PZT based thin films and piezoelectric micromachined ultrasonic transducers (pMUTs)
Washington State University
Master of Science (MS), Washington State University
2005
Handle:
https://hdl.handle.net/2376/400
Abstract
This thesis elaborates the research work done to achieve piezoelectric micromachined ultrasonic transducers (pMUTs) devices for medical imaging with better properties in terms of coupling efficiency, reliability and bandwidth. The objective was approached with optimizing materials and design parameters. Lead zirconate titanate (PZT) based piezoelectric thin films were used as the active element for these devices and the PZT material properties such as polarization values, dielectric constant, ferroelectric fatigue resistance, sintering temperature and others, were further improved by doping with zinc, strontium and yttrium. Wherein, strontium showed improved dielectric and polarization values, zinc showed lower sintering temperature and higher polarization values and yttrium resulted in improved ferroelectric fatigue resistance of the film. Finally, the doped PZT composition was optimized as 52/48 PZT + 2%Zn + 2%Sr for next step, the device fabrication. Flexural mode of vibration was used to create frequencies in the range of 1-4 MHz using PZT coated silicon membrane. Two independent designs X and Y were separately evaluated to understand the effect of membrane dimension, top gold electrode dimension and effective membrane area covered by it on the resonance frequency and coupling coefficient. Doped optimized PZT solution was used as the active material for device fabrication. Variation in the resonance frequency as a function of membrane dimension for both the designs was established. Optimum position and width of top gold electrode for design X corresponding to different membrane dimension was identified and an expansion of 10[mu]m beyond membrane width was found to be most effective. For design Y also gold electrode of (+) 10[mu]m gave better results then (-) 10[mu]m. Efficiency decreased on increasing gap width from 20[mu]m to 30[mu]m for design Y. Fabricated device was also characterized by running hysteresis curve, ferroelectric fatigue and FESEM pictures of the cross section and back side of the membrane.
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Details
- Title
- Optimization of PZT based thin films and piezoelectric micromachined ultrasonic transducers (pMUTs)
- Creators
- Abhishek Dalakoti
- Contributors
- Susmita Bose (Degree Supervisor)
- Awarding Institution
- Washington State University
- Academic Unit
- Mechanical and Materials Engineering, School of
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University; [Pullman, Washington] :
- Identifiers
- 99900525176001842
- Language
- English
- Resource Type
- Thesis