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Academic Calendar

Event Scheduled for Aug 2, 2017

 

Event: PhD Dissertation Defense: M. Tumerkan Kesim

Location: IMS-159

Time: 01:00 pm

Details of Event:
PhD Dissertation Defense

Presenter: M. Tumerkan Kesim

Major Advisor: Dr. S Pamir Alpay

Associate Advisors: Dr. Avinash M. Dongare, Dr. Serge M. Nakhmanson, Dr. Mark Aindow, Dr. Seok-Woo Lee.

Date: Wednesday, August 2, 2017

Time: 1:00 pm

Room: IMS-159

Title: Dielectric and Electrothermal Properties of Ferroelectric Multilayers and Superlattice Heterostructures

Abstract:
Artificial ferroelectric (FE) heterostructures show unique electrical properties compared to bulk and single-crystal FEs. The internal built-in electrical fields due to heterogenoeuos nature of the structure gives rise to electrical properties that are not observed in a bulk FE. Dielectric and electrothermal (pyroelectric and electrocaloric) properties of such multilayers and superlattice heterostructure are investigated using a non-linear thermodynamic model. The underlying reasons for the enhancement of electrical properties of FE heterostructures are analyzed based on the strain and built-in electrostatic fields that could be used as design parameters under realistic processing conditions of such materials. It is shown that the choice of multilayer/substrate pair, processing/growth temperature, and relative layer fraction of ferroelectric could be tailored to enhance dielectric and electrothermal properties of FE multilayers. For instance, large tunabilities (90% at 400 kV/cm) are possible in carefully designed barium strontium titanate-STO and PZT-STO even on Si for which there exist substantially large in-plane strains. It is also possible to obtain enhanced electrocaloric response from multilayers. 0.75BTO-0.25PZT and 0.35STO-0.65PZT bilayers show ~120% and 65% increase in electrocaloric response, respectively, compared to PZT films on Si for ΔE=500 kV/cm. It is possible to obtain enhanced dielectric and pyroelectric response from PZT-STO superlattices (SLs), especially with increased number of repeating unit for a fixed thickness. It is possible to avoid domain splitting in the FE and obtain enhanced properties with reduced overall transition temperature. For example, small bias pyroelectric coefficient of 8-unit symmetrical SLs is ~55% higher than that of a zero bias PZT monolayer reaching 0.045 C cm-2K-1.

Target Audience:

Sponsored By: Materials Science and Engineering Program

Pamphlet/Flyer: No Pamphlet/Flyer Available


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