Long-range interactions of surface charges on electrolyte films

Abstract

A surface charge at an electrolyte–insulator interface and its counterion cloud form an electric dipole, thus giving rise to a long-range interaction that has been identified as the usual dipolar interaction. In this paper, we show that the picture of interacting dipoles ceases to be valid for a thin film with a thickness smaller than the Debye screening length. Indeed, in this case, both parallel and antiparallel dipoles repel each other, with a force much stronger than expected from a dipolar interaction. This originates from the delocalization of the screening clouds in very thin films.