A rational consideration of space charge

Abstract

Space charge formation and its increase with field under DC conditions is not a mystical phenomenon. The increase in space charge with applied field is an obvious and inevitable result of the interaction of field-dependent current density with spatially inhomogeneous resistivity. For common polymeric dielectrics, the current density makes a transition from a linear function of field to an exponential function of field at around 10 kV/mm. This causes a similar transition in the sample space charge in the same field region. However, this transition has no obvious connection with aging, and if it does prove to have a connection, the driving force is the rapidly increasing current density and not the space charge, which is a result thereof. As to the issue of the accuracy of space charge measurements, it may be more important to focus on providing a physical mechanism for 1-eV deep traps at an average separation of 3 nm within a polymeric dielectric. This would bring about the ability to engineer important dielectric properties as well as improved understanding of the physical basis of aging and other important phenomena in dielectrics.