Space-charge distributions in electron-beam charged Mylar and Kapton films

The laser-induced pressure pulse method was used to determine space-charge distributions in 22-μm films charged with 10 to 40 keV electron beams. For relatively low deposited-charge densities corresponding to surface potentials below 300 V, two charge layers develop, one at the surface of the samples and one at a depth corresponding approximately to the electron range. For higher deposited-charge densities, when breakdown in the surrounding air occurs during pressurization, the surface-charge layer is positive. For deposited-charge densities in excess of 1 μC/cm², the space-charge layer is broader and, in Kapton, located deeper than for smaller charge densities. Heating of the samples to 110°C reduced the charge without broadening the charge layers