Graduation Semester and Year
Fall 2025
Document Type
Dissertation
Degree Name
Doctor of Philosophy in Physics and Applied Physics
Department
Physics
First Advisor
Joseph H. Ngai
Abstract
Multifunctional complex oxides exhibit a variety of properties that have the potential to enable novel functionalities in nano- and microelectromechanical systems (N/MEMS). These materials exhibit strong coupling between their electrical, mechanical, and thermal properties, enabling unique device functionalities that are difficult to achieve with conventional semiconductors. Among this material, the perovskite oxide Ba₁₋ₓSrₓTiO₃ (BSTO) is particularly attractive because its ferroelectric-paraelectric phase behavior can be tuned through both composition and temperature. This tunability allows the study of functionalities that emerge from mechanical coupling across dissimilar oxide silicon interfaces, as well as from intrinsic ferroelectricity, and phase-transition dynamics. Here we present the electromechanical response of ultra-thin, single-crystalline Ba₁₋ₓSrₓTiO₃ (x = 0, 0.90, 1) that has been integrated on Si(100). This serves as a model system for examining how interfacial strain coupling, ferroelectric domain activity, and near-transition domain dynamics together determine the functional behavior of oxide microresonators.
Structurally coupling mechanically dissimilar materials enables novel functionalities that do not exist in either material alone. For SrTiO₃ (x = 1), we find that the significant mismatch in thermal expansion coefficients between STO and Si generates a tensile strain in the oxide layer, resulting in a higher resonant frequency.
Dynamic aspects of ferroelectric domain behavior can give rise to novel functionalities that are non-volatile in nature. For BaTiO₃ (x = 0), we find that momentary mechanical stress applied to the microbridges using sub nano-Newton forces can induce non-volatile changes in mechanical resonance. The non-volatile changes are analyzed within the context of quasi-stable ferroelastic domains that become dynamic under applied stress, thereby leading to changes in the Young's modulus. This work advances our understanding of how domains wall dynamic influence mechanical behavior and their potential for designing tunable resonators in next generation sensing technologies.
Phase transitions in ferroelectric oxides induce dramatic changes in domain wall motion, making it easier to study the dissipation that occurs at these transitions. We have investigated the dynamic behavior of ferroelectric domains wall in Ba₁₋ₓSrₓTiO₃ (x = 0.90) at phase transitions. As the phase transition is approached, the resonance peak becomes broader and flatter, indicating increased damping and energy loss. At the transition, a sudden drop in resonance frequency and a sharp peak highlights the point of maximum dissipation caused by domain wall motion. Hence, this study provides insights into energy dissipation mechanisms in ferroelectric systems.
Disciplines
Condensed Matter Physics
License
This work is licensed under a Creative Commons Attribution-NonCommercial-No Derivative Works 4.0 International License.
Recommended Citation
Guragain, Deepa, "PROBING THE MECHANICAL BEHAVIOR AND FUNCTIONALITY OF Ba₁₋ₓSrₓTiO₃ (x = 0, 0.90, 1) MICROBRIDGE RESONATORS INTEGRATED ON SILICON" (2025). Physics Dissertations. 187.
https://mavmatrix.uta.edu/physics_dissertations/187