Abstract
Improved resistive switching memory characteristics by controlling the formation polarity in an IrOx/Al2O3/IrOx-ND/Al2O3/WOx/W structure have been investigated. High density of 1 × 1013/cm2 and small size of 1.3 nm in diameter of the IrOx nano-dots (NDs) have been observed by high-resolution transmission electron microscopy. The IrOx-NDs, Al2O3, and WOx layers are confirmed by X-ray photo-electron spectroscopy. Capacitance-voltage hysteresis characteristics show higher charge-trapping density in the IrOx-ND memory as compared to the pure Al2O3 devices. This suggests that the IrOx-ND device has more defect sites than that of the pure Al2O3 devices. Stable resistive switching characteristics under positive formation polarity on the IrOx electrode are observed, and the conducting filament is controlled by oxygen ion migration toward the Al2O3/IrOx 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 105 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.
Highlights
Many oxide materials such as NiOx [1,2,3,4], HfOx [5,6], Cu2O [7], Gd2O3 [8], TaOx [9,10], TiO2 [11], ZrO2 [12,13], AlOx [14,15,16], Na0.5Bi0.5TiO3 [17], SrTiO3 [18], and so on have been reported for nanoscale nonvolatile resistive switching random access memory (ReRAM) applications
The resistive switching random access memory (ReRAM) device with layer-by-layer has been observed by high-resolution transmission electron microscopy (HRTEM), energy dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS) analyses
A large memory window of approximately 1.2 V is observed under a sweeping gate voltage of ± 7 V for the IrOx-ND device, while a small memory of 0.3 V is observed for the pure Al2O3 chrage-trapping layers (Figure 3b)
Summary
Many oxide materials such as NiOx [1,2,3,4], HfOx [5,6], Cu2O [7], Gd2O3 [8], TaOx [9,10], TiO2 [11], ZrO2 [12,13], AlOx [14,15,16], Na0.5Bi0.5TiO3 [17], SrTiO3 [18], and so on have been reported for nanoscale nonvolatile resistive switching random access memory (ReRAM) applications. Improved resistive switching parameters such as set/reset voltages, low resistance state (LRS)/high resistance state (HRS), switching cycles, read endurance of > 105 times, and extrapolated 10 years data retention at 85°C of the IrOx-ND ReRAM device under positive formation polarity (PF) have been reported.
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