SUBJECT: Ph.D. Dissertation Defense
BY: Steven Brewer
TIME: Friday, August 18, 2017, 2:00 p.m.
PLACE: Love Building, 210
TITLE: Radiation Hardness in Ferroelectric Thin Films For MEMS Applications
COMMITTEE: Dr. Nazanin Bassiri-Gharb, Chair (ME)
Dr. Peter Hesketh (ME)
Dr. Chaitanya Deo (ME)
Dr. Josh Kacher (MSE)
Dr. Ronald Polcawich (US Army Research Laboratory)


The continuous development of microelectronics devices with lower power consumption and reduced weight and footprint has necessitated high-performance materials, capable of fulfilling multiple functional roles. Ferroelectric materials, such as lead zirconate titanate (PZT), boast large dielectric, polarization, and electromechanical responses, making them ideal for microelectromechanical systems (MEMS) sensors and actuators, energy harvesters, multilayer ceramic capacitors (MLCC), etc. However, many of the most compelling applications for these devices – for space travel, satellite communication, and nuclear energy – require sustained operation in radiation-hostile environments. Radiation has been shown to substantially degrade the functional response of materials; therefore, understanding the factors influencing radiation interaction with ferroelectric materials is critically important. This work presents a multifaceted approach to understanding radiation-matter interactions in ferroelectric thin films, focusing on an array of critical interfaces in the material stack. Studies on gamma-irradiated PZT thin films with variations of top electrode material, microstructure, layer crystallization interfaces, dopant concentration, and residual stress revealed that radiation modifies point defects, specifically oxygen vacancies. These radiation-modified oxygen vacancies are highly mobile, accumulate and order at interfaces, suppress polarization, pin ferroelectric domain wall motion, and subsequently degrade a film’s functional response. To comprehensively study radiation-induced defects, a phenomenological model was developed to quantify defect interactions in ferroelectric materials as a function of total ionization dose (TID) and related to functional response changes. This thesis furthers the fundamental scientific understanding of radiation interactions with ferroelectric materials further as well as offering engineering approaches for design of radiation-hard ferroelectric thin films for MEMS and microelectronics devices.