A new device for contactless studies of dielectrics

A new device, based on force measurements, has been developed for contactle ss studies of space charges in dielectrics. An electronic microforce balanc e is used to measure the force exerted on a sphere suspended above the surf ace of a dielectric sample. The application of a bias voltage to the sphere allows to separate the contributions to the force of the dielectric matrix and of space charges. Furthermore, the well-defined geometry used gives ac cess to a precise modeling of the setup response function. Translation of t he sample allows the mapping of charge distributions over large areas, with a lateral resolution limited by the size of the probe. A new type of exper iment, taking advantage of the potentialities of the setup to study charge transport phenomena in dielectrics without preliminary implantation of char ges, is also presented, and the first results obtained on polyethylene are discussed. (C) 1999 American Institute of Physics. [S0034-6748(99)03104-4].