Improved Resistive Switching Memory Characteristics Using Core-Shell IrOx Nano-Dots in Al2O3/WOx Bilayer Structure

Abstract

Improved resistive switching memory characteristics in an IrOx/Al2O3/IrOx-ND/Al2O3/WOx/W structure are investigated in this study. Core-shell iridium-oxide (IrOx) nano-dots (NDs) with a small diameter (∼2 nm) and high-density (0.7 × 1013/cm2) are observed by high-resolution transmission electron microscopy (HRTEM). The IrOx-NDs, Al2O3, and WOx layers are also confirmed by both HRTEM and X-ray photo-electron spectroscopy (XPS) analyses. Large number of electrons (with density of 8.9 × 1018/cm3) in the core-region and holes (with density of 7.1 × 1018/cm3) in the shell-region can be trapped in the IrOx-NDs under a small sweeping gate voltage of ±5 V. The IrOx-NDs in an Al2O3/WOx bilayer structure have an excellent uniformity of the SET and RESET voltages, an applicable ratio of high/low resistance state (>50), a long read endurance of 105 times and an extrapolated 10 years data retention at 85°C. Owing to the high charge-trapping density and nano-filament formation through the small size of the core-shell IrOx-NDs, the improvement of resistive switching performance is evident in comparison to that of the pure Al2O3 film in an IrOx/Al2O3/WOx/W structure. This study is not only important for improving the performance of IrOx-ND ReRAM devices but also helpful for designing a low power nanoscale nonvolatile memory in future.