Formation polarity dependent improved resistive switching memory characteristics using nanoscale (1.3 nm) core-shell IrO(x )nano-dots

Improved resistive switching memory characteristics by controlling the formation polarity in an IrO(x)/Al(2)O(3)/IrO(x)-ND/Al(2)O(3)/WO(x)/W structure have been investigated. High density of 1 × 10(13)/cm(2 )and small size of 1.3 nm in diameter of the IrO(x )nano-dots (NDs) have been observed by high-resolution transmission electron microscopy. The IrO(x)-NDs, Al(2)O(3), and WO(x )layers are confirmed by X-ray photo-electron spectroscopy. Capacitance-voltage hysteresis characteristics show higher charge-trapping density in the IrO(x)-ND memory as compared to the pure Al(2)O(3 )devices. This suggests that the IrO(x)-ND device has more defect sites than that of the pure Al(2)O(3 )devices. Stable resistive switching characteristics under positive formation polarity on the IrO(x )electrode are observed, and the conducting filament is controlled by oxygen ion migration toward the Al(2)O(3)/IrO(x )top electrode interface. The switching mechanism is explained schematically based on our resistive switching parameters. The resistive switching random access memory (ReRAM) devices under positive formation polarity have an applicable resistance ratio of > 10 after extrapolation of 10 years data retention at 85°C and a long read endurance of 10(5 )cycles. A large memory size of > 60 Tbit/sq in. can be realized in future for ReRAM device application. This study is not only important for improving the resistive switching memory performance but also help design other nanoscale high-density nonvolatile memory in future.