SCHEDULED MAINTENANCE
Current oscillations in iodine-doped polyethylene film
Abstract
Very low frequency (∼10–1 Hz) regular current oscillations may be induced in iodine-doped polyethylene films when subjected to electric fields in excess of about 3 × 107 V m–1. The oscillations are similar whether iodine is introduced from aqueous KI electrodes or from the dry vapour. The frequency depends on film thickness and iodine concentration and has an activation energy of ∼1.2 eV. Most significantly, it decreases with increasing field suggesting that space charge domains are propagating in the films encouraged by a negative differential charge carrier mobility-field characteristic. This is confirmed by direct measurement. The acceptor action of iodine probably generates mobile electron vacancies in the polymer chains, the effective mass of which increases with field to give the negative characteristic.
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