Relaxation currents in poly-4-vinylphenol dielectrics: Trapping and macroscopic polarization

Abstract

The trapping currents and the macroscopic polarization–depolarization currents were observed together for a series of on-off switching of O2 plasma-treated and UV-treated poly-4-vinylphenol (PVP) dielectrics mixed with methylated poly (melamine-co-formaldehyde) (MMF).Initially, both O2 plasma and UV created trap states on the PVP surface; however, prolonged O2 plasma or UV promoted cross-linking of the PVP (MMF 40wt.%) dielectric, and reduced the macroscopic polarization. Filtering of PVP solutions was also helpful in reducing the polarization.The slowly decreasing currents were ascribed to the trapping and buildup of charged-traps at the interface of PVP and the electrode, and this impedes the injection of further charges from the contacts.The macroscopic depolarization was found to be reduced with increased cross-linking. It is suggested that the macroscopic polarization–depolarization currents may possibly be related to free ions from the remnant hydroxyl groups inside the leakage channels.