Discrete tunneling current fluctuations in metal–water–metal tunnel junctions.

We have studied electron tunneling through water between two metal electrodes supported on a solid substrate and observed random fluctuations in the tunneling current between two discrete levels. The two-level fluctuations persist when changing the concentration and the valency of the ions, and pH of the water solutions. A given two-level fluctuation is, in general, not affected by the applied bias voltage, but it is usually disrupted by changing the width of the tunnel gap. We attribute the discrete conductance fluctuations to random trapping or escaping of a single electron in or from a localized state in the tunnel gap. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]