| This thesis focuses on combining knowledge gained from experiments and theoretical modeling to create better dielectric materials. Using fundamental insights gained by performing experiments and therefore understanding the spectrum of dielectric responses measured, we have been able to pinpoint areas where the models being used are not accurately describing the response of the material. By understanding the assumptions made by and the physics behind the models being used, we have been able to design experiments that measure the phenomena the models are trying to replicate. These insights have lead to the initial development better models that accurately capture the nature of the materials and their responses and to the creation of high performing dielectric materials.;First, we focus on nanoscale dipole sources in polymer matrices. By utilizing synthetic techniques that allow for control of the (i) interface between the nanoparticles and polymer and that (ii) don't require mechanical mixing of the inorganic particle and organic polymer, we were able to focus on the physics of the dielectric response and not the defects. From this we conclude that traditional effective media mixing equations are too simple to accurately predict the dielectric responses for materials that are most promising for capacitor applications. Also, by thorough characterization of the composites at high fields, we have been able to draw conclusions about the true energy storage promise of these types of materials. By creating a large series of related samples and probing these materials structurally, mechanically, and electrically (at low field, high field, low frequency, and high frequency), we have developed a vast data base of material characteristics. This set of composites with one type of polymer, 10 possible nanofillers, 5 possible shell thicknesses, and at least 5 (and up to 20) different volume fractions made for each nanofiller type, create a huge library from which understanding of the average or "representative" response, and outlier response of these complex materials has been gained. From this work we can conclude that size, shape, and aspect ratio of the nanoparticle fillers and the shell thickness are critical to low loss and good recoverable energy storage, and that there is a push-pull relationship to improving capacitance without creating leakage as the volume fraction of fillers is increased.;Second, molecular based dielectrics are studied for their use in unconventional transistor applications. Instead of high energy storage this application requires dielectrics that are thin, high capacitance, smooth, easily processed from solution, and flexible with many types of semiconductor materials. However, the polymer nanocomposites and the molecular dielectrics are basically made from the same components, insulating regions, and regions of dipolar response. The fabrication of the original self-assembled nanodielectric materials was extensively studied to insure dependable production of consistent, reproducible, high performing dielectric layers. This processing has shown that when reporting all characteristics of a dielectric both the representative behavior and the outlier behavior are critical to overall performance, especially for more complex device structures after proof-of-principle devices. By systematically studying the leakage and capacitance of these molecular structures a new set of molecular dielectrics have been developed that give lower leakage and higher capacitance. |
