Space charge distribution measuring system using PVDF piezoelectric thin film

A space charge density distribution measuring system based on a PPP (piezoelectrically induced pressure pulse wave) method was constructed. The pressure pulse wave is generated by pulse-driven piezoelectric PVDF (polyvinylidene fluoride) thin film as a piezoelectric pulse generator. Thin aluminum plate is used as a shield electrode which electrically separates between the pressure pulse generator and the sample holder. This thin shield electrode reduces attenuation and dispersion of the pressure pulse wave compared to the former system. From a PPP response to a sheet charge that is artificially made on a dielectric thin film, space resolution of the system is estimated to be about 7 /spl mu/m. Using space charge distribution measurement and TSDC (thermally stimulated discharge current) measurement, charge behaviour of the corona-charged polytetrafluoroethylene (PTFE teflon/sup TM/) thin films are studied.