Origin of equilibrium space charge potentials in ionic crystals

Abstract

A simple model is constructed which illustrates the origin of ionic space charge regions at surfaces of ionic crystals of the AgCl and NaCl type. The model differs from previous treatments by considering explicitly the binding states of ions on surfaces and the surface density of such states. The problem is then formally analogous to that of an intrinsic semiconductor with a fixed density of surface electronic states. The space charge potential difference is determined by the occupation statistics of the surface ionic states. The model predicts significant differences from previous calculations of the temperature variation of the surface space charge potential.