Improved Resistive Switching Memory Characteristics Using Core-Shell IrOxNano-Dots in Al2O3/WOxBilayer Structure

Improved resistive switching memory characteristics in an IrO x /Al 2 O 3 /IrO x -ND/Al 2 O 3 /WO x /W structure are investigated in this study. Core-shell iridium-oxide (IrO x ) nano-dots (NDs) with a small diameter (∼2 nm) and high-density (0.7 × 10 13 /cm 2 ) are observed by high-resolution transmission electron microscopy (HRTEM). The IrO x -NDs, Al 2 O 3 , and WO x layers are also confirmed by both HRTEM and X-ray photo-electron spectroscopy (XPS) analyses. Large number of electrons (with density of 8.9 × 10 18 /cm 3 ) in the core-region and holes (with density of 7.1 × 10 18 /cm 3 ) in the shell-region can be trapped in the IrO x -NDs under a small sweeping gate voltage of ±5 V. The IrO x -NDs in an Al 2 O 3 /WO x 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 10 5 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 IrO x -NDs, the improvement of resistive switching performance is evident in comparison to that of the pure Al 2 O 3 film in an IrO x /Al 2 O 3 /WO x /W structure. This study is not only important for improving the performance of IrO x -ND ReRAM devices but also helpful for designing a low power nanoscale nonvolatile memory in future.