Graduation Year

2025

Document Type

Dissertation

Degree

Ph.D.

Degree Name

Doctor of Philosophy (Ph.D.)

Degree Granting Department

Electrical Engineering

Major Professor

Jing Wang, Ph.D.

Committee Member

Sylvia Thomas, Ph.D.

Committee Member

Norma Alcantar, Ph.D.

Committee Member

Arash Takshi, Ph.D.

Committee Member

Jiangfeng Zhou, Ph.D.

Keywords

Thin-Film Transducer, Finite Element Methods, Microelectromechanical Systems, Lorentz Force Magnetometer, Quality Factor

Abstract

This dissertation significantly advances the field of micro-electro-mechanical systems (MEMS) resonators by exploring novel post-fabrication tuning techniques, electrode configuration effects, and innovative sensor applications for thin-film piezoelectric-on-silicon (TPoS) resonator devices. Driven by the increasing demand for tunable, high-precision and robust MEMS resonators in radio frequency (RF) applications such as sensing, timing, and filtering, this research aim to provide foundational knowledge and practical solutions for overcoming existing technological limitations. The dissertation is organized into three main research thrusts, each addressing critical challenges and opportunities in the design, fabrication, and application of TPoS MEMS resonators.

The first research thrust investigates an innovative frequency trimming and performance enhancement technique for TPoS MEMS resonators through Joule heating-induced localized annealing. This approach significantly improves resonator performance by selectively tuning resonance frequencies post-fabrication, effectively reducing motional impedance across various resonator designs. The reliability and effectiveness of localized annealing represents a substantial leap forward, offering a versatile solution for precise frequency control in RF MEMS applications.

The second research thrust investigates a previously unexplored aspect of MEMS resonator design—the rotational orientation of the top electrode—and its impact on vibrational mode selection and piezoelectric transduction efficiency. By systematically rotating the top electrode with respect to the resonator body, the study investigates how this geometric variation influences the excited vibrational modes and the resulting piezoelectric transduction. This investigation uncovers critical relationships between electrode orientation and resonator performance, therefore offering practical design guidelines for enhancing mode selection and signal quality in sensor and oscillator applications.

The third thrust applies the tailor-designed TPoS resonator technology to develop a Lorentz force magnetometer, showcasing a novel sensor capable of detecting magnetic fields with exceptional sensitivity. In this application, the resonator is engineered to respond to external magnetic fields by exploiting the Lorentz force effect. The device demonstrates the capability to detect and measure magnetic fields with high sensitivity, leveraging the high quality factor and low motional impedance of the TPoS resonators. This work shows initial promise to expand the utility of piezoelectric MEMS resonators beyond traditional timing and filtering applications, thus highlighting their potential as core components in advanced sensing systems.

Collectively, the dissertation makes significant contributions to better understanding and practical realization of tunable, high-performance TPoS MEMS resonators. The outcomes not only enhance fundamental understanding but also set a robust technological foundation for future innovations in MEMS-enabled RF systems, sensor technologies, and advanced microsystem applications, thus promising transformative impacts on next-generation wireless communication, sensing, and timing system solutions.

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