VARIATION OF THE RELATIVE PERMITTIVITY OF CHARGED DIELECTRICS

The variation of the relative permittivity of charged dielectrics with trapped charge density has been investigated by a time-resolved curre nt method, in conjunction with a mirror image method employing a scann ing electron microscope. The calculation is made by a mathematical exp ression derived from classical electromagnetic theory. It is found tha t the relative permittivity of the charged area in the polymethylmetha crylate sample increases with the trapped charge density and saturates at a certain value of the trapped charge density. These observations have been discussed by analogy with the dielectric saturation occurrin g at a high applied external electric field. (C) 1998 American Institu te of Physics.