Thermal Vapor Deposition and Characterization of Polymer-Ceramic Nanoparticle Thin Films and Capacitors

Abstract

Research on alternative energies has become an area of increased interest due to economic and environmental concerns. Green energy sources, such as ocean, wind, and solar power, are subject to predictable and unpredictable generation intermittencies which cause instability in the electrical grid. This problem could be solved through the use of short term energy storage devices.

Capacitors made from composite polymer:nanoparticle thin films have been shown to be an economically viable option. Through thermal vapor deposition, we fabricated dielectric thin films composed of the polymer polyvinylidine fluoride (PVDF) and the ceramic nanoparticle titanium dioxide (TiO₂). Fully understanding the deposition process required an investigation of electrode and dielectric film deposition. Film composition can be controlled by the mass ratio of PVDF:TiO₂ prior to deposition. An analysis of the relationship between the ratio of PVDF:TiO₂ before and after deposition will improve our understanding of this novel deposition method.

X-ray photoelectron spectroscopy and energy dispersive x-ray spectroscopy were used to analyze film atomic concentrations. The results indicate a broad distribution of deposited TiO₂ concentrations with the highest deposited amount at an initial mass concentration of 17% TiO₂.

The nanoparticle dispersion throughout the film is analyzed through atomic force microscopy and energy dispersive x-ray spectroscopy. Images from these two techniques confirm uniform TiO₂ dispersion with cluster size less than 300 nm. These results, combined with spectroscopic analysis, verify control over the deposition process.

Capacitors were fabricated using gold parallel plates with PVDF:TiO ₂ dielectrics. These capacitors were analyzed using the atomic force microscope and a capacohmeter. Atomic force microscope images confirm that our gold films are acceptably smooth. Preliminary capacohmeter measurements indicate capacitance values of 6 nF and break down voltages of 2.4 V.

Our research on the deposition process will contribute to the understanding of PVDF/TiO₂ composite thin films. These results will lead to further investigation of PVDF/TiO₂ high density energy storage capacitors. These capacitors can potentially increase the efficiency of alternative energy sources already in use.