Relaxation currents from macroscopic depolarization in poly-4-vinylphenol dielectrics

Polarization and depolarization currents were obtained from a capacitor structure with poly-4-vinylphenol (PVP) dielectrics by on-off switching. A single Debye relaxation was revealed for thin films; while some dispersion appeared for thick samples. The relaxation time constant (τ) of the currents was ∼1 s, and the polarization density depended on the type of top electrodes. The slow relaxation at on-off switching corresponded to a much higher susceptibility (χ ≈ 103), compared to that (χ ≈ 100) of the PVP molecular dipoles, suggesting the existence of macroscopic dipoles. Meanwhile, fast (τ < ∼0.1 ms) polarization and depolarization of the molecular dipoles in PVP layers were detected by measuring a P–E hysteresis loop at a high frequency. In both cases, the electric susceptibility decreased for thin (∼100–1000 nm) PVP layers, showing the dominant effects of the interfacial states.