Multilevel Resistive Switching in Heterogeneous Oxide System Based on TiO 2 /Al 2 O 3 Bilayers for ReRAM Applications: Problems and Prospects

Thin film oxide bilayers are prospective systems for application in ReRAM devices. Its resistance state could be electrically tuned in the range of seven orders of magnitude. Together with a bipolar resistive switching occurred relatively to the previously tuned resistance state, these structures could significantly increase the density of ReRAM and provide a multilevel logic implementation at the hardware level. The main problem hampering integration of TiO 2 /Al 2 O 3 bilayers with multilevel resistive switching in the current ReRAM technology is a deviation of its actual electrical behavior over the switching cycles. Based on the analysis of our experimental results, we develop a model, which explains possible reasons for electrical parameter deviation in heterogeneous oxide systems based on TiO 2 /Al 2 O 3 bilayers. The proposed approach makes possible to describe quantitatively a bipolar resistive switching in TiO 2 /Al 2 O 3 bilayers, relatively to an arbitrary chosen level of the system's resistance in the whole range of the resistances amounting to almost seven orders of magnitude.