Multibit Operation of $\hbox{TiO}_{x}$ -Based ReRAM by Schottky Barrier Height Engineering

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.