Observation of fluctuation-induced tunneling conduction in micrometer-sized tunnel junctions

Abstract

Micrometer-sized Al/AlOx/Y tunnel junctions were fabricated by the electron-beam lithography technique. The thin (approximate to 1.5-2 nm thickness) insulating AlOx layer was grown on top of the Al base electrode by O-2 glow discharge. The zero-bias conductances G(T) and the current-voltage characteristics of the junctions were measured in a wide temperature range 1.5-300 K. In addition to the direct tunneling conduction mechanism observed in low-G junctions, high-G junctions reveal a distinct charge transport process which manifests the thermally fluctuation-induced tunneling conduction (FITC) through short nanoconstrictions. We ascribe the experimental realization of the FITC mechanism to originating from the formations of "hot spots" (incomplete pinholes) in the AlOx layer owing to large junction-barrier interfacial roughness. Copyright 2012 Author(s). This article is distributed under a Creative Commons Attribution 3.0 Unported License. [http://dx.doi.org/10.1063/1.4749251]