The frequency dependent dielectric breakdown in some thin polymers

Dielectric breakdown of thin polyvinylcarbazole (PVK), polyimide (PI) and polymethyl methacrylate (PMMA) films prepared by vapor deposition polymerization or spin coating has been investigated for various ac voltages. The self-healing breakdown takes place at the peak of the applied voltage. The ac breakdown strength of these films decreases with temperature, and it increases with frequency in the range of 10Hz-3kHz except the case of PMMA in the high temperature range above 120°C. The gold electrodes give the lower breakdown strength than the aluminum electrode in PVK and PI films. The frequency dependent breakdown has been explained in terms of the field enhancement due to the hole space charge, which establishes the conductive path leading to the breakdown.