Zero bias features in self-assembling tunnel junctions

A marked suppression of the conductance near zero bias voltage is a feature common to many electron tunneling systems and has been attributed to several different mechanisms including Coulomb blockade and non-equilibrium tunneling. We observe zero bias features (ZBFs) in self-assembling tunnel junctions in which the oxide layer of a traditional metal-insulator-metal junction is replaced by an atomically-thin gas film. We also find small conductance steps superimposed on the otherwise smoothly varying ZBF. Examination of the derivative of the junction conductance in this region reveals peaks, similar to those observed in point contact spectroscopy, that appear to be correlated with the phonon density of states in the metal electrodes. (C) 2000 Elsevier Science B.V. All rights reserved.