Effect of Oxidation Amount on Gradual Switching Behavior in Reset Transition of Al/TiO₂-Based Resistive Switching Memory and Its Mechanism for Multilevel Cell Operation

Oxygen Vacancy Density Dependence with a Hopping Conduction Mechanism in Multilevel Switching Behavior of HfO2-Based Resistive Random Access Memory Devices

“…The forming voltage was observed to be at 1.8 V at a compliance current of 1 mA. While there was consistent switching and low cycle-to-cycle variability, it was more important to observe the presence of gradual switching characteristics in the RESET state, thus confirming the existence of multilevel states in the HRS. , In the investigation of multiple device characteristics, the device-to-device variability of the resistive switching devices with an average SET voltage of 0.5 V and V stop at −1.2 V was also shown in a resistance box plot in Figure b, read at −0.1 V. It was found that the median ON/OFF ratio was about 50×, a ratio large enough for multiple level resistance switching states to occur.…”

Filamentary physics and modelling in redox-based resistive devices

“…This makes the RESET process a clear factor to look for in determining whether multi-level states are possible in any RRAM stack. [106,159] A gradual switching would allow different resistance states to be obtained by varying Vstop, however the slope of the gradual switching also plays a role in determining whether multi-level states can be obtained. However, a closer observation revealed that at higher voltages such as -1.3 V to -1.5 V, the spacing between HRS are very close to one another, which might suggest a difficulty in differentiating between the different HRS for the multi-level states.…”