Mechanism of High Temperature Retention Property (up to 200 °C) in ZrO2-Based Memory Device With Inserting a ZnO Thin Layer

In this letter, the switching mechanism of the ZrO₂-based RRAM devices with the uniform and reliable reliability properties is investigated. The stability of memory window can be improved by inserting a ZnO thin film with the nonstoichiometric property between Ti top electrode and ZrO₂ layer. Compared with ZrO₂ film, the ZnO one can easily perform the oxidation-reduction reaction for stable endurance properties. In addition, through Gibbs free energy comparison of TiO_x, ZrO₂, and ZnO, we can demonstrate that the Gibbs free energy contributes to the retention performance. The device with thin ZnO layer has stable retention performance at high temperature (200 °C) due to its higher Gibbs free energy value than TiOx.