Electron-beam poling of very thin PVDF and VDF-TrFE copolymer films

A novel method of electron-beam poling of very thin (d≈100 nm) polyvinylidenefluoride (PVDF) and vinylidenefluoride-trifluoroethylene copolymer (VDF-TrFE) films, cast from solution on a well-polished metal substate, is presented. The penetrating electron beam passes through the thin polymer film, and its main energy dissipates inside the metal support. Due to the secondary electron emission from the film surface a positive surface potential is left on the polymer, producing a poling field toward the grounded metal substrate. Using a chopped electron beam (E₀=5 keV to 30 keV) poling patterns have been created on the film. These polarized regions, having a lateral resolution in the submicron range, are subsequently imaged in the scanning electron microscope at low beam intensity using the potential contrast method. The mechanism for the generation of contrast is discussed