Electrochemical nature of metal-insulator interfaces

At the interface between a metal and a dielectric (e.g., vacuum, sulfur hexafluoride, polymers, oils, detonated nitromethane, etc.) a variety of charge transfer events can take place which, basically, are electrochemical in nature. Such interfacial charge transfers are usually investigated by solid-state physicists and electrical engineers; for the fundamental understanding of the phenomena involved, it is necessary, however, to think of these interfacial charge transfers in the conceptual framework of electrochemical physics. Some typical cases of electrochemical processes at metal-dielectric interfaces are described. For example, metal-vacuum-metal sandwiches subjected to high-field dielectric breakdown can be shown to behave as metal-electrolyte-metal electrochemical cells. The field-induced dielectric breakdown of the vacuum creates a low-pressure plasma that acts as a gaseous electrolyte in that it contains ions and electrons that conduct electricity. The situation obtained at such interfaces is quite similar to that at metal-electrolyte interfaces