Effects of annealing on the optical and electronic properties of poly (vinylidene fluoride-trifluoroethylene) copolymer thin films

Thin films of vinylidene fluoride with trifluoroethylene [P(VDF-TrFE)] copolymer have been deposited onto bare Si and SiO2 by spin casting from methylethylketone solutions. The structures and optical and electronic properties for P(VDF-TrFE) films after vacuum and forming gas annealing were studied. The degree of structural order and the crystallinity determined by X-ray diffraction were increased with the thermal annealing time. Ellipsometry spectroscopy were employed to investigate the changes in the thickness, refractive indices n, and the anisotropic properties. The results reflected that the n was increased with the thermal annealing time and temperature, and the anisotropy of the annealed films was strengthened with the annealing time and temperature. Metal-polymer-(oxide)-semiconductor capacitors were used to measure the static dielectric constant K and interfacial electronic properties of P(VDF-TrFE) on Si which the K increase with film thickness and thermal annealing. The interface at Al-P(VDF-TrFE) and/or P(VDF-TrFE)-Si affect the K value which is sensitive for films thinner than 120 nm. The Si-P(VDF-TrFE) interface quality determined using capacitance-voltage and current-voltage measurementswas found to be improved after forming gas annealed.