The local oxidation produced by the tip of an atomic force microscope scanning on a thin metallic film allows to define narrow oxide lines, thus providing 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. In this letter we show that tunneling barriers can also be produced with Ti films covering small gold islands. The gold islands significantly shorten the effective tunneling distance, allowing to observe temperature-independent electron tunneling across the lateral barriers. The mixed Ti/Au tunnel barriers reveal Coulomb blockade effects which may be used for single-electron devices consisting of a single oxide line. (C) 2000 American Institute of Physics. [S0003-6951(00)03514-2].