Atomic-sized Pd Tunneling Junction Memory with 25ns Switching Capacity and Enhanced Endurance.

We demonstrate an atomic-sized Pd tunneling junction memory that can operate in a vacuum, N2, or ambient environment. The device was fabricated by a simple 2-step electron-beam lithography/lift-off process and an electromigration process. Calculation based on quantum point contact model indicated the size of the tunneling gap is between 0.1 and 2nm, and the switching between high-resistance state and low-resistance state is achieved by a migration of a few atoms near the junction. The device's RESET speed is 25ns, and the ON/OFF ratio is from 2 to 103, with an endurance of 1000 cycles. We proposed a phenomenological model to explain the reason for the imperfection of device performance, which could be useful for circuit design. It may be derived from two different migration processes, dominated by rapid changing electric field and current-induced Joule heat accumulation to affect the device performance, respectively. Compared to other reported works, our devices have the same fast RESET speed, better endurance, and potential for low power applications.