Comparison of neat and photo-crosslinked polyvinylidene fluoride-co-hexafluoropropylene thin film dielectrics formed by spin-coating

We report the characterization of photo-crosslinked polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP) thin film, metal-insulator-metal capacitors fabricated using standard semiconductor processing techniques. We characterize the capacitors using in-situ vibrational spectroscopy during thermally-assisted poling and correlate the Fourier transform infrared spectroscopy (FTIR) results with X-ray diffraction (XRD) results. FTIR analysis of the neat PVDF-HFP showed alpha -> beta transformations during poling at room temperature and at 55 degrees C. alpha -> beta transformations were observed for the crosslinked polymer only during poling at 55 degrees C. XRD data revealed that photo-crosslinking caused the polymer to partially crystallize into the beta-phase. The similar behavior of the neat and crosslinked samples at 55 degrees C suggests that a higher activation energy was needed for alpha -> beta transformations in crosslinked PVDF-HFP during poling. Electrical measurements showed that photo-crosslinking had no significant effect on the dielectric constant and dielectric loss of PVDF-HFP. However, the dielectric strength and maximum energy density of the crosslinked polymer were severely reduced. (C) 2013 Elsevier B. V. All rights reserved.