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Title: Characterization and Modelling of Anomalous Properties of SiO2, Si3N4 and Al2O3 Nanolaminates
Committee:
Dr. Jeffrey Davis, ECE, Chair, Advisor
Dr. Muhannad Bakir, ECE
Dr. Azad Naeemi, ECE
Dr. John Cressler, ECE
Dr. Hamid Garmestani, MSE
Abstract: Current research on (~ 20 nm) SiO2, Si3N4 and Al2O3 nanopowders (NPs) has revealed anomalous increases in permittivity over conventional bulk values due to localized dipole polarization effects on the surface of these NP particles. The present work has proposed alternative material structures, which are constructed using nanolithographic techniques to explore the high-polarization surface effects seen in NP research. This work has particularly focused on fabricating and modelling anomalous behavior of the permittivity of nanolaminate devices constructed from a combination of SiO2, Si3N4 and Al2O3 materials. The three main takeaways of this work are as follows: 1) Strong surface dipole formation leads to high average permittivity at the air interfaces of SiO2, Si3N4 and Al2O3. Specifically, the behavior at these interfaces were investigated and modelled using FEM simulations to identify the average surface permittivity values over a specified volume. 2) As air breaks down at low electric field, the aforementioned devices were encapsulated with different combinations of SiO2, Si3N4 and Al2O3 layers in interdigitated electrode (IDE) configurations. The subsequent measurements showed significant deviations in capacitances, which are attributed to the dipole and bond formations that occur at the interfaces between the nanolaminate layers. The nanolaminate IDE structures have electric fields that are parallel to the dielectric interfaces, which could activate the highly polarizable interfacial regions more effectively than the traditional parallel plate electrode (PPE) structures. 3) Because the materials in this study inherently have high breakdown field strengths there is a potential energy storage opportunity for future capacitive devices that utilize these experimental observations and simulation results. Preliminary projections indicate that capacitive devices with a high-density of nanolaminates with laminate thicknesses from 2-5 nm could produce devices with volumetric energy densities that are orders of magnitude higher than conventional supercapacitors.
