Properties of metal-polymer-metal structures observed with space charge mapping techniques — II. Radiation induced space charge distributions

The techniques described in the preceding paper are utilized to observe the space charge distributions that are generated in metal-polymer-metal samples subjected to x-ray irradiation in the presence of an electric field. Our previous radiation-induced conductivity studies on poly(ethylene terephthalate) and doped poly(ethylene terephthalate) films have shown that holes are immobile in that material and electrons are the dominant photocarrier species. Consistent with those measurements, we find a positive space charge distribution trapped adjacent to the cathode in poly(ethylene terephthalate) samples after x-ray irradiation. The width of that heterocharge distribution is compared with the estimated electron Schubweg. Ongoing experiments studying the dose and electric field dependence of the space charge formation will be described. These measurements reveal injection currents that limit heterocharge formation. The presence of space charge limited currents in radiation-induced conductivity data will be examined.