Soung Kyu Park

Effects of electron-beam irradiation on conducting polypyrrole nanowires

Conducting polypyrrole (PPy) nanowires (NWs) were irradiated by a relatively high energy (300 keV–2 MeV) electron-beam (e-beam) generated from a linear electron accelerator in an atmospheric environment. From the current-voltage characteristics of pristine and 2 MeV e-beam irradiated PPy NWs, we observed a dramatic variation in resistance from 8.0×102 to 1.45×108 Ω, that is, we observed a transition from conducting states to nonconducting states through the e-beam irradiation. To discern conformational changes and the doping states of PPy NWs through the e-beam irradiation, we measured Raman and ultraviolet-visible absorption spectra for the PPy NWs. As the energy of the e-beam irradiation increased, we observed that the PPy NWs were changed from doping states to dedoping states with conformational modification including the variation in π-conjugation length.

Low Dielectric Constant of MeV Ion-Implanted Poly(vinylidene fluoride)

Poly (vinylidene fluoride)(PVDF) samples were implanted by using high energy (MeV)F2+ and Cl2+ ions. We observed that AC dielectric constant of the ion-implanted PVDF samples decreased from 10.5 to 2.5 at 1 kHz as the ion dosage increased from 1011 to 3 × 1014 ions/cm2. From differential scanning calorimetry experiments, we observed that PVDF samples become more disordered state through the ion implantation. The decrease of the number of bonding of C-H and C-F and the increase of unsaturated bonding were observed from X-ray photoelectron spectroscopy experiments. The emission of HF and H2 molecules during the ion implantation was detected by residual gas analyzer spectrum. Based upon the results, we analyzed that the low AC dielectric constant of the MeV ion-implanted PVDF samples originated from the reduction of polarization due to the structural change of the CF2 molecules in the MeV ion-implanted PVDF samples.