Paper TF-TuP3
Vacuum Phase Deposition of Thin Films of poly(2,6-dimethyl-1,4-phenylene oxide)/Polystyrene/Silver Nanostructured Composites and Their Electrical and Surface Adhesion Characteristics

Tuesday, October 16, 2007, 6:00 pm, Room 4C

Thin nanocomposite films comprising Poly(2,6-dimethyl-1,4-oxyphenylene)/Polystyrene and Poly(2,6-dimethyl-1,4-oxyphenylene)/Silver were fabricated using an electron beam assisted physical vapor co-deposition technique. The fabrication process is a one step novel vapor phase co-deposition of polymers and metal on substrates maintained at room temperature in a vacuum chamber. Glass, Polyethylene terephtalate, aluminum and gold were used as substrates during experiments. Nanocomposite film topologies were studied with various techniques including AFM, X-Ray diffraction, Raman Spectroscopy, Scanning Electron Microscopy and finally static contact angle measurements to estimate surface adhesion properties as a function of silver volume filling. Fabrication of the thin film structures involved evaporation and subsequent condensation of materials from specially designed tungsten crucibles. The crucibles were heated in a controlled manner by bombarding with electrons generated by applying high voltage to tungsten filaments. The deposition system had four crucibles allowing four different components to be co-deposited simultaneously. Before deposition of nanocomposites, preliminary and separate experiments were conducted in order to establish evaporation rates of Polystyrene and Poly(2,6-dimethyl-1,4-oxyphenylene) (a.k.a PPO). Different metal volume filling ratios in the thin film nanocomposites were achieved by adjusting relative evaporation rates of polymers and silver. AFM and electron micrographs of the deposited nanocomposites featured a nanoporous surface morphology. Using a multi-fluid contact angle technique (Kaeble plots) surface energy of the nanocomposites was estimated as a function of metal filling. Composite surface energy polarity increased as a function of increasing silver filling. Above a critical metal filling the composites were conductive, on the other hand particularly below this critical metal filling, based on forward bias I-V measurements, nanocomposite film-metal interfaces displayed Schottky barrier type characteristics. In addition, a number of thin film capacitors were also made by co-deposition of PPO and metal on Aluminum substrates. The thin film capacitors exhibited capacitance densities of about 4-7 nF/cm² up to 80 MHz frequency.