Fabrication of Ti/TiOx tunneling barriers by tapping mode atomic force microscopy induced local oxidation

We use an atomic-force microscope operating in a dynamic modus, commonly called tapping mode, to completely oxidise through thin 5 nm titanium films using the very local electric field between the tip and the sample. Tapping mode local oxidation minimizes tip degradation and therefore enhances resolution and reliability. By working under a controllable environment and measuring the resistance in situ while oxidising we are able to fabricate well-defined isolating Ti-TiOx-Ti barriers as small as 15 nm. Their conductance shows an exponential dependence on the oxide width, thereby identifying tunneling as the dominant conduction mechanism. From the nonlinear current-voltage characteristic a tunneling barrier height of 178 meV is derived. (C) 1997 American Institute of Physics.