SUBJECT: Ph.D. Proposal Presentation
   
BY: Steven Brewer
   
TIME: Thursday, October 13, 2016, 1:45 p.m.
   
PLACE: MRDC Building, 3515
   
TITLE: Response Enhancement and 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 (Army Research Laboratory)
 

SUMMARY

Perovskite ferroelectrics boast large dielectric, piezoelectric, and pyroelectric responses, making them attractive for use in a multitude of functional devices and applications, such as mechanical logic elements, optical sensors and transducers, precision positioners, energy harvesting systems, and especially microelectromechanical systems (MEMS) sensors and actuators. Of particular interest are concepts for autonomous, millimeter-scale robotics for performing duties in radiation-hostile environments, such as in space or facilities processing radioisotopes. Previous studies have mostly demonstrated radiation-hard dielectric behavior in ferroelectrics. However, a substantial component of the large functional response of these materials is derived from defect-defect interactions, and therefore, radiation-induced defects can be expected to substantially affect the electromechanical response.

As these applications continuously require increased performance and further miniaturization, more robust materials with enhanced multifunctional response are necessary to drive them at smaller length scales. The electromechanical response in ferroelectric thin films is greatly dependent on film thickness, decreasing substantially below one micron, due to intrinsic and extrinsic size effects of the material. The proposed work studies critical interfaces in ferroelectric thin film material stacks - i.e. the film-electrode, film-elastic layer, film-substrate, and grain and phase boundary interfaces - and their effects on the functional response of ferroelectric material stacks for device applications. Additionally, the work aims to establish a fundamental understanding of defect-defect and radiation-matter interactions at these interfaces. Leveraging this understanding, we demonstrate appropriate engineering approaches to increase radiation hardness and enhance dielectric and electromechanical response in ferroelectric thin films, thus providing avenues to smaller, more capable MEMS and microelectronics devices.