Pre- and post-breakdown switching behaviour in ultrathin SiO₂layers detected by C-AFM

Ultrathin SiO2 films (3-6 nm) have been electrically characterized with a conductive atomic force microscope. This technique allows the electrical characterization of areas of ~100 nm2, which are comparable to the area of breakdown spots. Sequences of voltage ramps on fixed oxide locations have been applied to induce the oxide degradation and its conduction properties have been analysed within the nanometre scale range. In particular, on-off fluctuations before and after breakdown are reported on single breakdown spots.