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

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

Challenges and Applications of Emerging Nonvolatile Memory Devices

Emerging nonvolatile memory (eNVM) devices are pushing the limits of emerging applications beyond the scope of silicon-based complementary metal oxide semiconductors (CMOS). Among several alternatives, phase change memory, spin-transfer torque random access memory, and resistive random-access memory (RRAM) are major emerging technologies. This review explains all varieties of prototype and eNVM devices, their challenges, and their applications. A performance comparison shows that it is difficult to achieve a “universal memory” which can fulfill all requirements. Compared to other emerging alternative devices, RRAM technology is showing promise with its highly scalable, cost-effective, simple two-terminal structure, low-voltage and ultra-low-power operation capabilities, high-speed switching with high-endurance, long retention, and the possibility of three-dimensional integration for high-density applications. More precisely, this review explains the journey and device engineering of RRAM with various architectures. The challenges in different prototype and eNVM devices is disused with the conventional and novel application areas. Compare to other technologies, RRAM is the most promising approach which can be applicable as high-density memory, storage class memory, neuromorphic computing, and also in hardware security. In the post-CMOS era, a more efficient, intelligent, and secure computing system is possible to design with the help of eNVM devices

Compact model for organic thin-film transistor with Gaussian density of states

Developing a compact model for organic thin-film transistors (OTFTs) would be significant for designing organic circuits. Contrasting the traditional silicon transistors, OTFTs are theorized using hopping transport and a Gaussian density of states. In this work, we present a new compact model for OTFTs by introducing hopping transport theory, a Gaussian density of states, and a physical mobility model. Our compact model is completely based on surface potential and its simulations do not require any threshold voltage. Simulations based on this model agree well with experimental data

Highly-stable (< 3% fluctuation) Ag-based Threshold Switch with Extreme-low OFF Current of 0.1 pA, Extreme-high Selectivity of 109 and High Endurance of 109

1

Highly-stable (< 3% fluctuation) Ag-based Threshold Switch with Extreme-low OFF Current of 0.1 pA, Extreme-high Selectivity of 109 and High Endurance of 109 Cycles

2

Transformation of threshold volatile switching to quantum point contact originated nonvolatile switching in graphene interface controlled memory devices.

Resistive switching devices based on binary transition metal oxides have been widely investigated. However, these devices invariably manifest threshold switching characteristics when the active metal electrode is silver, the dielectric layer is hafnium oxide and platinum is used as the bottom electrode, and have a relatively low compliance current (&lt;100 μA). Here we developed a way to transform an Ag-based hafnium oxide selector into quantum-contact originated memory with a low compliance current, in which a graphene interface barrier layer is inserted between the silver electrode and hafnium oxide layer. Devices with structure Ag/HfO x /Pt acts as a bipolar selector with a high selectivity of &gt;108 and sub-threshold swing of ∼1 mV dec-1. After introducing a graphene interface barrier, high stress dependent (forming at +3 V) formation of localized conducting filaments embodies stable nonvolatile memory characteristics with low set/reset voltages (&lt;±1.0 V), low reset power (6 μW) and multi-level potential. Grain boundaries of the graphene interface control the type of switching in the devices. A good barrier can switch the Ag-based volatile selector into Ag-based nonvolatile memory

Variability Improvement of TiO_<i>x</i>/Al₂O₃ Bilayer Nonvolatile Resistive Switching Devices by Interfacial Band Engineering with an Ultrathin Al₂O₃ Dielectric Material

Variability control over the resistive switching process is one of the key requirements to improve the performance stability of the resistive random access memory (RRAM) devices. In this study, we show the improvement of the variability of the resistive switching operation in the TiO_<i>x</i>/Al₂O₃ bilayer RRAM devices. The achievement is based on the thickness engineering of the Al₂O₃ layer. A thick Al₂O₃ dielectric actively takes part to control the resistive switching behavior; on the contrary, the ultrathin layer of Al₂O₃ behaves as the tunnel barrier in the structure. At lower voltage, the low resistance state conductions follow the trap-assisted tunneling and Fowler–Nordheim tunneling for the thick and thin Al₂O₃ RRAMs, respectively. Finally, the variation control in device forming, SET voltage distribution, high resistance state, low resistance state, and resistance ratio is achieved with the TiO_<i>x</i>/Al₂O₃ bilayer RRAM devices by interfacial band engineering with an ultrathin Al₂O₃ dielectric material