Field and electron beam-induced luminescence phenomena in polypropylene thin films

Field-induced luminescence of insulating polymers is an exciting field of research. Being intrinsically related with the high-field electronic properties of the material, it provides a way to investigate electrical ageing and breakdown processes. It is particularly suited for those materials used in high field applications, e.g. thin films of polypropylene in capacitors. One of the puzzling aspects of electroluminescence in wide band gap polymers is that the emission spectra are only reproduced under electron beam irradiation. In this communication, we report for the first time the field and electron beam induced luminescence in polypropylene films. Measurements were performed on 17 µmthick bi-oriented polypropylene films. The home-designed electron gun provides electrons of up to 10 keV in energies. Emission spectra acquired for different beam energies are compared to the electroluminescence spectra obtained under AC stress for fields in the range 150–300 kV/mm. The nature of the excitation process in field and electron beam-induced luminescence is discussed together with the nature of emitting species and their significance for ageing study.