Electron Beam Probing of Space Charge in Pet Films

A diffuse, monoenergetic electron beam of variable energy is used to measure space charge profiles in thin polyethylene terephthalate (PET) films. A quantitative model of the method used for the profile calculations is presented. Results are given of measured charge profiles set up both by electron beam deposition and by voltage poling. The method is shown to have a spatial resolution of about 0.5 ¿m and a minimum detectable charge density of about 0. 5×102 C/m3 for PET. Inherent experimental problems are identified and potential uses of the method are discussed.