Property Enhancements of Dielectric Nanoparticles via Surface Functionalization

This thesis describes the surface modification of barium strontium titanate nanoparticles for use in polymer/ceramic composite thin film capacitors with resultant improved dielectric and film-making properties. Phosphonic acid-type ligands proved to be most effective for surface conjugation to the surface of the barium strontium titanate nanoparticles. Amine-terminated ligands proved to be effective at removing surface adsorbed water before being almost entirely removed during the sample washing stage. Carboxylic acid terminated ligands proved to adhere less well to the nanoparticle than the phosphonic acid, but resulted in thin films with a higher dielectric constant, which was more stable in the measured frequency range than the phosphonic acid. This is seen via a systematic change in thin film variables, including ligand length, ligand reactive head, presence of polymer composite, and concentration of ligand. The nanoparticles were synthesized, ligands attached, then a series of thin film capacitors were fabricated to study the chang in dielectric properties. The results show a stabilized dielectric constant over a wide frequency range, a dramatically decreased loss, and better film-making properties. The new materials presented in this study are potentially useful as dielectrics for low-energy-density/low-loss capacitors