Title

Ferroelectric multilayers and heterostructures for high performance tunable microwave devices applications

Date of Completion

January 2007

Keywords

Engineering, Materials Science

Degree

Ph.D.

Abstract

Ferroelectric multilayers and heterostructures have attracted a significant amount of interest in the past decade due to their unique properties compared to their homogenous counterparts. A number of peculiar phenomena, such as gigantic dielectric permittivity, enhanced spontaneous polarization, high dielectric tunability, and special phase transformation characteristics have been discovered in various ferroelectric heterostructures. ^ This study is a theoretical and experimental effort to understand the potential applications of ferroelectric multilayers in high performance tunable devices and transducers. A comprehensive non-linear thermodynamic modeling incorporating theory of elasticity and principles of electrostatics is developed to analyze interlayer coupling, interface effects, and the role of internal stresses in ferroelectric multilayers and heterostructures. The theoretical results are then utilized to guide the deposition of ferroelectric multilayers with high dielectric tunability, low dielectric loss, and temperature insensitive dielectric permittivity, which have potential applications in next generation tunable microwave devices. The experimental results are then explained in the context of the developed theory. Theoretical and experimental results also indicate that the piezoelectric response can be enhanced significantly due to a built-in potential and the commensurate strain field. ^