CHARGE-TRANSFER ACROSS METAL-SIO2 INTERFACES

Charge transfers very easily across a metal-SiO2 interface even though the charge is completely immobile in the oxide. To a first approximation, the charge transfer is such as to maintain a certain fixed field across the interface; as we should expect if there were a high density of electron states on the insulator surface, able rapidly to exchange electrons with the metal. However, detailed investigation shows that the interfacial field is not maintained exactly constant but depends to some extent on the previous history; for example, an electric field influences charge transfer even if it is switched off before the contact is broken.