Electronic surface states of a dielectric film on a metal substrate

An electron near the surface of liquid or solid He, Ne, or H2 is excluded from the interior of the medium because of a net repulsive interaction with the atoms or molecules composing it. If a layer of such a material is situated on a conductor these electrons may become localized near the insulator-vapor interface, bound there by polarization forces. We discuss the properties of these states and determine their lifetime prior to electron tunneling through the insulator to the metal.