Bias polarity dependent local electrical conduction in resistive switching TiO₂ thin films

The localized electrical conduction behaviour of a resistive switching TiO₂ film was examined by conductive atomic force microscopy (CAFM). Localized filamentary electrical conduction was well resolved with a negative tip bias with respect to the Pt bottom electrode whereas almost uniform electrical conduction was observed with a positive bias. The bias dependence of the CAFM result was attributed to local electrochemical reactions mediated by the high electric field near the CAFM tip. A positive tip bias extended the electrically conducting area much more than the actual tip-surface contact area presumably due to facilitated oxygen loss by the high electric field.