We demonstrate memory property using Ni nanocrystals with mean diameter of 9nm embedded in HfO2 high-k dielectric that are formed via a self-assembly process by sputtering and rapid thermal annealing. X-ray photoelectron spectroscopy shows that Ni penetrates into the 5nm HfO2 after high temperature annealing above 800°C in N2. However, the diffusion is suppressed by N incorporation into HfO2 by NH3 annealing. Metal-oxide-semiconductor structures were fabricated with Ni nanocrystals embedded in HfO2. An additional counterclockwise hysteresis of 2.1V due to the charge trapping properties of the Ni nanocrystals was observed from a ±5V sweep during capacitance–voltage electrical measurement.

No abstract

No abstract

Low temperature crystallization of high permittivity Ta oxide using an Nb oxide thin film for metal/insulator/metal capacitors in dynamic random access memory applications J. Vac. Sci. Technol. B 23, 80 (2005); 10.1116/1.1829060Effect of growth temperature and postmetallization annealing on the interface and dielectric quality of atomic layer deposited HfO 2 on p and n siliconThe formation of tungsten nanocrystals ͑W-NCs͒ on atomic-layer-deposited HfAlO/ Al 2 O 3 tunnel oxide was demonstrated for application in a memory device. It was found that the density and size distribution of W-NCs are not only controlled by the initial film thickness, annealing temperature, and time, but also by the metal/tunnel oxide interface structure. Well-isolated W-NCs with an average diameter of 5 nm and a surface density of 5 ϫ 10 11 cm −2 were obtained by applying a thin Al 2 O 3 wetting layer onto HfAlO tunneling oxide. A large flatband voltage shift of 5.7 V was observed from capacitance-voltage measurement when a bias voltage up to ±4 V was applied.

Post-metal annealing temperature-dependent forming-free resistive switching memory characteristics, Fowler-Nordheim (F-N) tunneling at low resistance state, and after reset using a new W/WO3/WOx/W structure have been investigated for the first time. Transmission electron microscope image shows a polycrystalline WO3/WOx layer in a device with a size of 150 × 150 nm2. The composition of WO3/WOx is confirmed by X-ray photo-electron spectroscopy. Non-linear bipolar resistive switching characteristics have been simulated using space-charge limited current (SCLC) conduction at low voltage, F-N tunneling at higher voltage regions, and hopping conduction during reset, which is well fitted with experimental current-voltage characteristics. The barrier height at the WOx/W interface for the devices annealed at 500 °C is lower than those of the as-deposited and annealed at 400 °C (0.63 vs. 1.03 eV). An oxygen-vacant conducting filament with a diameter of ~34 nm is formed/ruptured into the WO3/WOx bilayer owing to oxygen ion migration under external bias as well as barrier height changes for high-resistance to low-resistance states. In addition, the switching mechanism including the easy method has been explored through the current-voltage simulation. The devices annealed at 500 °C have a lower operation voltage, lower barrier height, and higher non-linearity factor, which are beneficial for selector-less crossbar memory arrays.

The complementary resistive switching (CRS) characteristics using an IrOx/GdOx/Al2O3/TiN single cell are observed whereas the bipolar resistive switching (BRS) characteristics are observed for the IrOx/GdOx/TiN structure. Transmission electron microscope and energy dispersive X-ray spectroscopy depth profile show crystalline GdOx film and the presence of higher amount of oxygen at both IrOx/GdOx interface and Al2O3 layer. Inserting thin Al2O3 layer, the BRS is changed to CRS. This CRS has hopping distance of 0.58 nm and Poole-Frenkel current conductions for the “0” and “1” states, respectively. A schematic model using oxygen vacancy filament formation/rupture at the TE/GdOx interface and Al2O3 layer has been illustrated. This CRS device has good endurance of 1000 cycles with a pulse width of 1 μs, which is very useful for future crossbar architecture.

Controlled resistive switching by using an optimized 2 nm thick MoS 2 interfacial layer and the role of top electrodes (TEs) on ascorbic acid (AA) sensing in a TaO x -based resistive random access memory (RRAM) platform have been investigated for the first time. Both the high-resolution transmission electron microscopy (HRTEM) image and depth profile from energy dispersive X-ray spectroscopy confirm the presence of each layer in IrO x / Al 2 O 3 /TaO x /MoS 2 /TiN structure. The pristine device including the IrO x TE with the 2 nm thick interfacial layer shows the highest uniform rectifying direct current endurance >1000 cycles and a large rectifying ratio >3.2 × 10 4 , and a high nonlinearity factor >700 is obtained, greater than that of Pt and Ru TEs. After formation, this IrO x device produces bipolar resistive switching characteristics and a long program/erase (P/E) endurance >10 7 cycles at a low operation current of <50 μA with small pulse width of 100 ns. The stressed device shows a reduced Al 2 O 3 /TaO x interface from the HRTEM image, which is owing to O 2− ions' migration toward TiN electrode. By adjusting the RESET voltage and current level, consecutive >100 complementary resistive switching as well as long P/E endurance of >10 6 cycles are obtained. Schottky barrier height modulation at a low field is observed owing to reduction− oxidation of the TE, which is evidenced through reversible AA detection. At a higher field, Fowler−Nordheim tunneling and hopping conduction are observed. Ascorbic acid detection with a low concentration of 1 pM by using a porous IrO x /Al 2 O 3 / TaO x /MoS 2 /TiN RRAM device directly is an additional novelty of this work, which will be useful in future for early diagnosis of scurvy.

Resistive switching with best structural optimization by taking 100 devices of each structure including tungsten/iridium (W/Ir) top electrode effects and dopamine sensing by inserting 2 nm thick Al2O3 interfacial layer in TaOx‐based memory platform are reported for the first time. Statistical analysis of device‐to‐device switching uniformity for the formation voltage, low resistance state, and high resistance state is executed at low current compliance of 30 μA by inserting 2 nm thick Al2O3 layer underneath of W electrode in W/Al2O3/TaOx/TiN structure. Incorporation of defective layer (TaOx) into Ta2O5 layer is clearly observed from the high‐resolution transmission electron microscope image of stressed device. A long program/erase endurance of >108 cycles under low current of 30 μA with pulse width of 100 ns and retention of >900 h at 85 °C is obtained. Diode‐like rectifying at 1 μA with higher ratio of >5000, nonlinearity factor of >300, and complementary resistive switching are achieved by using Ir electrode. Transport mechanism is dominated by Schottky conduction. Dopamine at a low concentration of 1 × 10−12m is detected through porous Ir in Ir/Al2O3/TaOx/TiN structure owing to oxidation at the Ir/Al2O3 interface for the first time, which will be useful for early diagnosis of human diseases.