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We demonstrate a high-performance selection device by utilizing the concept of crested oxide barrier to suppress the sneak current in bipolar resistive memory arrays. Using a TaO(x)/TiO(2)/TaO(x) structure, high current density over 10(7) A cm(-2) and excellent nonlinear characteristics up to 10(4) were successfully demonstrated. On the basis of the defect chemistry and SIMS depth profile result, we found that some Ta atoms gradually diffused into TiO(2) film, and consequently, the energy band of the TiO(2) film was symmetrically bent at the top and bottom TaO(x)/TiO(2) interfaces and modified as a crested oxide barrier. Furthermore, the one selector-one resistor device exhibited significant suppression of the leakage current, indicating excellent selector characteristics.

This paper describes the resistive switching of a cross-point cell array device, with a junction area of 100 nm x 100 nm, fabricated using ultraviolet nanoimprinting. A GdO(x) and Cu-doped MoO(x) stack with platinum top and bottom electrodes served as the resistive switching layer, which shows analog memory characteristics with a resistance ratio greater than 10. To demonstrate a neural network circuit, we operated the cell array device as an electrically modifiable synapse array circuit and carried out a weighted sum operation. This demonstration of cross-point arrays, based on resistive switching memory, opens the way for feasible ultra-high density synapse circuits for future large-scale neural network systems.

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We demonstrated multibit operation using a 250-nm Ir/TiO x /TiN resistive random access memory by Schottky barrier height engineering. A Schottky barrier was formed by the interface between a high-work-function Ir top electrode and n-type TiO x . The conducting path, which was composed of oxygen vacancies, was generated in a low-resistance state, whereas a Schottky barrier was reproduced in a high-resistance state (HRS) due to the high concentration of oxygen by the electric field. By changing the reset operation voltage, we successfully engineered the Schottky barrier height, resulting in the modulation of the HRS current and demonstrating the feasibility of multibit applications.Index Terms-Resistive random access memory (ReRAM), RRAM, Schottky barrier height modulation.