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Academic Calendar

Event Scheduled for Apr 16, 2018

Event: PhD Dissertation Defense - Manuel Rivas

Location: IMS-159

Time: 03:00 pm

Details of Event:
PhD Dissertation Defense

Presenter: Manuel Rivas
Major Advisor: Dr. Bryan Huey
Associate Advisors: Dr. Seok-Woo Lee, Dr. S. Pamir Alpay, Dr. Ryan Q. Rudy (ARL), Dr. Ronald G. Polcawich (ARL/DARPA)

Date: Monday, April 16th, 2018
Time: 3:00 PM
Place: IMS 159

Title: Iridium Oxide (IrO2) as a Top Electrode for Ferroelectric Micro-Electro-Mechanical Systems (MEMS) Devices for Radiation Rich Environments

The multifunctional properties of ferroelectric materials make them ideal components for numerous applications including for extreme environments such as space. Iridium oxide (IrO2) electrodes have been demonstrated to improve the lifetime of ferroelectric memory devices, however little is known about its influence on the electromechanical properties important for ferroelectric microelectromechanical systems (MEMS). The performance of thin film lead zirconate titanate (PZT) based MEMS is affected by the processing conditions, composition, device design, electrode materials, and the environment. This work details the development and characterization of iridium oxide electrodes for PZT based microelectromechanical and pyroelectric-harvesting systems, fabrication induced defects, and design of clamped vs unclamped devices. This work also considers the influence of iridium oxide top electrodes on the properties of PZT films and MEMS devices subjected to gamma and heavy ion radiation for applications in space and for evaluating nuclear material where human exposure must be kept to a minimum.
Using single point force measurements with an atomic force microscope, this work presents the first known experimental value of Young’s modulus for thin film IrO2 (262 GPa). It was discovered that iridium oxide films of different morphologies are produced by manipulating the reactive gas flow rate in a sputtering process. Planar IrO2 for piezoelectric applications was optimized at 60 sccm O2 flow rate deposited at 500°C. Nanostructured, 2D platelets are observed for high oxygen flow rates (100 sccm) producing a self-limiting dense columnar film as the base of the plate-like structures. While the plate-like region continues to grow with increased deposition at a rate of ~6nm/s, the dense film appears to reach a critical thickness of approximately 60 nm. Devices with iridium oxide top electrode appear to be more radiation resistant when compared to identically fabricated devices with a platinum (Pt) top electrode, when exposed up to 10 Mrad (Si) of gamma rays from a Co-60 source and an equivalent dose with heavy Fe ions. In situ measurements taken during Co-60 irradiation showed different degradation characteristics compared to the devices whose electrodes were left floating during irradiation. This shows the presence of an applied electric plays a role in the radiation induced defects.

Target Audience: Not Available

Sponsored By: Materials Science and Engineering Department

Pamphlet/Flyer: No Pamphlet/Flyer Available

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