Linear decay of charge in electrets

Abstract

The processes leading to very long lifetimes of implanted electric charge are discussed. A model assuming a competition between the rate of current carrier generation in activation processes, and the rate of carrier annihilation on electrodes and by free, implanted charge was considered. The discussed processes lead to a very pronounced decrease in electric conductivity, and in consequence to long lifetimes of implanted charge, in agreement with experimental data. The important feature of our model is that exponential decay of charge takes place only for short times—hours or days for polymers. For the longer periods—hundreds or thousands of years in the case of Teflon films—a linear decay is predicted. The importance of the shape of a dielectric plate and the unusual stability of thin electrets are also discussed.