Phenomenological Model of Electret State in Carnauba Wax Inferred from Electrical Conduction Measurements

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Abstract
Measurements of current‐voltage charactristics, isothermal discharge currents, and thermally stimulated current have been used to clarify the mechanism of formation of electret state in Carnauba wax. The results of such measurements are interpreted with the aid of an energy band model in which a set of localized energy levels, located in the gap of energy bands, acts as charge carrier traps. The gap is about 7.4 eV wide. In the neighborhood of electrode contact the traps have a uniform energy distribution which extends as far as 0.3 eV from the edge of the bands. In the bulk of the material the energy distribution of trapping states becomes exponential and extends all over the gap. The charges (electrons and holes) have a double origin: the injection from the electrodes and a thermally activated process in which electron‐hole pairs are produced. The homocharges arise because of trapping of the injected charges near the electrodes and the heterocharge because of trapping of electron‐hole pairs in the bulk of the material.

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