Modeling static charge dissipation on solids: An historical perspective

Gilbert was the first to recognize the specific character of electrics, materials able to attract a needle when rubbed. Four centuries later, the detailed understanding of this experiment remains delicate, even concerning one aspect only: charge dissipation after charging. The double nature of the material, dielectric and allowing charge transport, identified by Faraday, will participate. We examine here both aspects, following an historical perspective. Dielectric absorption, involving slow polarization mechanisms, can be related to a viscoelastic behavior of the material, as long as superposition principle applies. From Kohlrausch to modern spectroscopy, dielectric functions were proposed, and attempts were made to account for the general behavior, involving time power laws and stretched exponentials. Charge transport in insulating solids may be modeled using the concepts of carrier mobility and trapping. In disordered materials, dispersive transport has to be considered, due the broad distribution in trapping energies. This leads also to time power laws in the decay process. Hence both faces of the insulator, dielectric and conductive, often lead to the same dispersion in the time response of the signal. It may be related to intrinsic parameters of the material, like its fractal nature. It has also important practical consequences