Mesoscopic electronic devices made by local oxidation of a titanium film covering gold islands

The local oxidation produced by the tip of an atomic force microscope scann ing on a thin metallic film allows to define narrow oxide lines, thus provi ding a method to fabricate lateral tunnel junctions. In such devices, with rather thick tunnel junction barriers, the electrical transport is governed by thermally activated hopping rather than by direct electron tunneling. I n this letter we show that tunneling barriers can also be produced with Ti films covering small gold islands. The gold islands significantly shorten t he effective tunneling distance, allowing to observe temperature-independen t electron tunneling across the lateral barriers. The mixed Ti/Au tunnel ba rriers reveal Coulomb blockade effects which may be used for single-electro n devices consisting of a single oxide line. (C) 2000 American Institute of Physics. [S0003-6951(00)03514-2].