Effects of Stacking Sequence and Top Electrode Configuration on Switching Behaviors in ZnO-HfO2 Hybrid Resistive Memories

The resistive switching (RS) behavior of multilayered ReRAM devices is typically influenced by two aspects: the intrinsic properties of the dielectric multilayer, and other extrinsic contributions. In this study, we deposited and investigated bi-layered memories incorporating ZnO and HfO2 dielectrics. Different stacking sequences of the two oxides (ZnO/HfO2 and HfO2/ZnO) were employed to explore the intrinsic contribution of the bilayer microstructure, while different top electrode configurations (Pt and Ti) were utilized to demonstrate the extrinsic impact. All devices exhibit characteristic bipolar RS behavior, showcasing their functionality. But interestingly, the device with a Pt top electrode displays digital RS behavior, while the one with a Ti top electrode exhibits analog RS behavior. The completely different switching types observed during the reset process of the ZnO-HfO2 hybrid resistive memories are attributed to different interface charge migration process and structural charac-teristic. And as compared to the tailoring effect of stacking sequences (bilayer microstructure and oxide/oxide interface), the tailoring effect of top electrode configuration (electrode materials and oxide/electrode interface) is much stronger. Based on the latter, the switching ratio can be remarkably improved by at least two orders of magnitude, the reset voltage (energy consumption) can also be significantly reduced, and other discussed switching parameters can also show greater improvement. The comprehensive comparative analysis of intrinsic and extrinsic contributions provides valuable insights for exploring the RS mechanism and optimizing the design of bi-layered memory devices.