The characteristics and mechanism of conduction/set process in TiN∕ZnO∕Pt-based resistance random access memory devices with stable and reproducible nanosecond bipolar switching behavior were studied. The dependencies of memory behavior on cell area, operating temperature, and frequency indicate that the conduction mechanism in low-resistance states is due to electrons hopping through filament paths. We also identify that the set process is essentially equivalent to a soft dielectric breakdown associated with a polarization effect caused by the migration of space charges under a low electric field stress. The generation/recovery of oxygen vacancies and nonlattice oxygen ions play a critical role in resistance switching.

Highly stable bipolar resistive switching behaviors of TiN/ZnO/Pt devices were demonstrated for the first time. The excellent memory characteristics including fast switching speed (<20 ns for set and <60 ns for reset), long retention (in the order of 10 5 s) and non-electroforming process were demonstrated. The bipolar switching behaviors can be explained by formation and rupture of the filamentary conductive path consisting of oxygen vacancies. The excellent bipolar switching behavior can be attributed to the significant amount of oxygen vacancies in ZnO film and the effect of TiN layer serving as an oxygen reservoir.

No abstract