Dielectric-breakdown-like forming process in the unipolar resistance switching of Ta2O5−x thin films

We report unipolar resistance switching (URS) in Ta2O5−x thin films. The current increased suddenly when we applied voltages up to 5–7 V to the pristine state of Pt/Ta2O5−x/Pt, Ni/Ta2O5−x/Pt, and Ti/Ta2O5−x/Pt cells. Just after this forming process, we observed a repetitive URS occurring independently of the electrodes. We found that the required voltages for the forming process did not depend on the top electrode type, but on the film thickness. These results suggest that the forming process is driven by a dielectric-breakdown-like phenomenon, and that URS occurs due to the formation and rupture of conducting channels inside the Ta2O5−x thin film.