Voltage and power-controlled regimes in the progressive unipolar RESET transition of HfO2-based RRAM.

Resistive switching (RS) based on the formation and rupture of conductive filament (CF) is promising in novel memory and logic device applications. Understanding the physics of RS and the nature of CF is of utmost importance to control the performance, variability and reliability of resistive switching memory (RRAM). Here, the RESET switching of HfO2-based RRAM was statistically investigated in terms of the CF conductance evolution. The RESET usually combines an abrupt conductance drop with a progressive phase ending with the complete CF rupture. RESET1 and RESET2 events, corresponding to the initial and final phase of RESET, are found to be controlled by the voltage and power in the CF, respectively. A Monte Carlo simulator based on the thermal dissolution model of unipolar RESET reproduces all of the experimental observations. The results contribute to an improved physics-based understanding on the switching mechanisms and provide additional support to the thermal dissolution model.

Resistive-switching crossbar memory based on Ni-NiO core-shell nanowires.

Resistive-switching memory (RRAM) is an emerging nanoscale device based on the localized metal-insulator transition within a few-nanometer-sized metal oxide region. RRAM is one of the most promising memory technologies for the ultimate downscaling of nonvolatile memory. However, to develop memory arrays with densities approaching 1 Tb cm(-2) , bottom-up schemes based on synthesis and assembly of metal oxide nanowires (NWs) must be demonstrated. A RRAM memory device based on core-shell Ni-NiO NWs is presented, in which the Ni core plays the role of the metallic interconnect, while the NiO shell serves as the active switching layer. A resistance change of at least two orders of magnitude is shown on electrical operation of the device, and the metal-insulator switching is unequivocally demonstrated to take place in the NiO shell at the crossing between two NWs or between a NW and a gold electrode strip. Since the fabrication of the NW crossbar device is not limited by lithography, this approach may provide a basis for high-density, low-cost crossbar memory with long-term storage stability.