Mechanisms of contact charging and charge accumulation: experiments on soda glass

Abstract

Charge transfer almost almost always occurs when a metal touches an insulator. In general, repeated contact to the same place will transfer additional charge (charge accumulation). In many materials charge accumulation is clearly related to conduction. It is usually supposed that charge accumulation occurs because the charge deposited by the contact diminishes by some conduction process, and the surface states emptied of charge can be refilled on the next contact. The author describes a series of experiments which indicate that this is not the mechanism of charge accumulation in soda glass. He concludes from his observations that conduction influences charge accumulation because it modifies the interfacial electric field between the glass and the contacting metal; the amount of charge transfer is controlled by this interfacial field rather than by the number of accessible states.