A comparison of space-charge distributions in electron-beam irradiated FEP obtained by using heat-wave and pressure-pulse techniques

In the present paper, heat wave (LIMM) and pressure pulse (LIPP) measurements of the space-charge distributions in electron-beam irradiated Teflon FEP (25 mu m thick) are reported. The space-charge profiles obtained by the two methods are compared over the whole sample thickness. From the LIMM with the back surface heat sink, the space-charge distribution can be found from the surface of illumination up to at least half of the sample thickness. For the position of the bulk space charge, the heat wave and LIPP response results agree with each other to within 1 mu m. By using LIMM, an additional negative charge layer near the surface is found if the electron-beam irradiation is carried out through the metallized sample surface.