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Modeling and Experimental Study of Bulk Acoustic Wave Resonator Sensor

Qin, Lifeng (2010) Modeling and Experimental Study of Bulk Acoustic Wave Resonator Sensor. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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Bulk acoustic wave (BAW) resonator as one of the simplest acoustic device, has been proven a most powerful tool for sensor applications with the advantage of precise frequency counting in electronic measurement. Meanwhile, with the improvement of device fabrication and material growth techniques, the resonator can be made with very small size, especially thin film bulk acoustic wave resonators (FBARs) based on ZnO and AlN have been attracted much interest for sensor application due to their high sensitivity induced by high resonance frequency. In this thesis, research focus is on the modeling and experimental study of bulk acoustic wave resonator sensor.Quartz thickness shear mode (TSM) resonator is adopted to characterize the viscoelastic properties of polymer nanocomposite thin films deposited on the resonators surface. The input electric admittance of multilayer loaded TSM acoustic wave resonator is firstly derived using transfer matrix method by taking into account the acoustic wave impedance of the polymeric layer. Nanocomposite thin films of multi-wall carbon nanotubes (MWCNTs) in copolymers of polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE) are deposited on TSM resonators through spin-on coating processing. The electric impedance spectra of the unloaded and loaded acoustic wave resonators are measured experimentally, and a data fitting approach is applied to extract the properties of the polymer nanocomposites films. It has been found that the thickness of the polymer layer plays a very important role in the extraction of the viscoelastic properties of the films through data fitting, and the reinforcement of the elastic shear modulus of polymer nanocomposite films is not significant. Quartz TSM resonator is also investigated for in-situ and real time detection of liquid flow rate. A 5MHz TSM quartz resonator is edge-bonded to the sensor mounting port of a special flow chamber with one side exposed to the flowing liquid and other side exposed to air. The fundamental, 3rd, 5th, 7th, and 9th resonant frequency shift due to flow pressure is found to be around 920 (Hz), 3572 (Hz), 5947 (Hz), 8228 (Hz) and 10300 (Hz) for flow rate variation from 0 to 3000 ml/min, which has a corresponding Reynolds number change from 0 to 822. Both theoretical and experimental investigation shows the resonant frequency shifts of different modes are quadratic with flow rate. The results indicate that quartz TSM resonators can be used for flow sensors with characteristics of simplicity, fast response, and good repeatability.FBARs based on c-axis tilted ZnO and AlN thin films have been theoretically analyzed. Material properties including elastic, dielectric and piezoelectric coefficients, bulk wave properties including acoustic velocity and electromechanical coupling coefficient, and impedance of FBARs are calculated and show strong dependence on the tilt angle of c-axis(¦È).Besides ¦È=90¡ã pure thickness shear mode occurs at 43¡ãfor ZnO and 46.1¡ãfor AlN, besides ¦È=0¡ã pure thickness longitudinal mode occurs at 65.4¡ã for ZnO and 67.1¡ãfor AlN. The electromechanical coupling coefficient of shear mode has a maximum value 13.1% at ¦È=33.3¡ãfor ZnO, and 6.5% at ¦È=34.5¡ãfor AlN; the maximum electromechanical coupling coefficient of longitudinal mode occurs at ¦È=0¡ãwith a value of 8.5% for ZnO, and 6% for AlN. The simulation results show that c-axis tilted ZnO and AlN thin films can provide more options for filter design and sensor application.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairWang, Qing-Mingqiw4@pitt.eduQIW4
Committee MemberLi, Guangyonggul6@pitt.eduGUL6
Committee MemberVipperman, Jeffrey S.jsv@pitt.eduJSV
Committee MemberSmolinski, Patrickpatsmol@pitt.eduPATSMOL
Committee MemberSlaughter, William S.wss@pitt.eduWSS
Date: 30 September 2010
Date Type: Completion
Defense Date: 16 April 2010
Approval Date: 30 September 2010
Submission Date: 24 May 2010
Access Restriction: 5 year -- Restrict access to University of Pittsburgh for a period of 5 years.
Institution: University of Pittsburgh
Schools and Programs: Swanson School of Engineering > Mechanical Engineering
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: BAW; AlN; quartz; ZnO; FBAR; resonator
Other ID:, etd-05242010-155727
Date Deposited: 10 Nov 2011 19:45
Last Modified: 15 Nov 2016 13:43


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