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Journal of the Electrochemical Society, Vol.159, No.2, H177-H182, 2012
Improved Resistive Switching Memory Characteristics Using Core-Shell IrOx Nano-Dots in Al2O3/WOx Bilayer Structure
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 (similar to 2 nm) and high-density (0.7 x 10(13)/cm(2)) 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 x 10(18)/cm(3)) in the core-region and holes (with density of 7.1 x 10(18)/cm(3)) 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 10(5) times and an extrapolated 10 years data retention at 85 degrees 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. (C) 2011 The Electrochemical Society. [DOI: 10.1149/2.067202jes] All rights reserved.