Charge Transfer Upon Contact Between Metals and Insulators

Abstract

The equilibrium charge distribution between substances in contact is calculated in the one-dimensional approximation for metal-insulstor and insulator-insulator contacts. The direction of charge transfer is such as to equalize the Fermi levels, and the magni tude of charge transferred depends on the positions of the energy bands in the substances in contact. For example, in an insulator it is possible to have a large charge density (∼ 10 ¹¹ esu) within a thin layer (∼ 10^-8 cm.) or a small charge density (∼ 10^-1 esu) in a thick layer (∼ 10^-1 cm.), to give the same potential shift (∼ 1 ev), depending on the relative position of the bands. The energy levels in most insulators of high resistiv ities are too poorly known to allow strict quantitative comparison with experiment, but the results permit a semiquantitative explanation of some observations on static electrification.