Abstract
Mutli-level switching in resistive memory devices enables a wide range of computational
paradigms, including neuromorphic and cognitive computing. To this end, we have developed a bilayer
tantalum oxide based resistive random access memory device using Hf as the oxygen
exchange layer. Multiple, discrete resistance levels were achieved by modulating the RESET pulse
width and height, ranging from 2 kX to several MX. For a fixed pulse height, OFF state resistance
was found to increase gradually with the increase in the pulse width, whereas for a fixed pulse
width, the increase in the pulse height resulted in drastic changes in resistance. Resistive switching
in these devices transitioned from Schottky emission in the OFF state to tunneling based
conduction in the ON state, based on I-V curve fitting and temperature dependent current measurements.
These devices also demonstrated endurance of more than 108 cycles with a satisfactory Roff/
Ron ratio and retention greater than 104 s
