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, common ly called tapping mode, to completely oxidise through thin 5 nm titani um films using the very local electric field between the tip and the s ample. Tapping mode local oxidation minimizes tip degradation and ther efore enhances resolution and reliability. By working under a controll able 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 conduct ion mechanism. From the nonlinear current-voltage characteristic a tun neling barrier height of 178 meV is derived. (C) 1997 American Institu te of Physics.