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.

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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.