Variability Improvement of TiO<sub><i>x</i></sub>/Al<sub>2</sub>O<sub>3</sub> Bilayer Nonvolatile Resistive
Switching Devices by Interfacial Band Engineering with an Ultrathin
Al<sub>2</sub>O<sub>3</sub> Dielectric Material
Variability control over the resistive
switching process is one
of the key requirements to improve the performance stability of the
resistive random access memory (RRAM) devices. In this study, we show
the improvement of the variability of the resistive switching operation
in the TiO<sub><i>x</i></sub>/Al<sub>2</sub>O<sub>3</sub> bilayer RRAM devices. The achievement is based on the thickness
engineering of the Al<sub>2</sub>O<sub>3</sub> layer. A thick Al<sub>2</sub>O<sub>3</sub> dielectric actively takes part to control the
resistive switching behavior; on the contrary, the ultrathin layer
of Al<sub>2</sub>O<sub>3</sub> behaves as the tunnel barrier in the
structure. At lower voltage, the low resistance state conductions
follow the trap-assisted tunneling and Fowler–Nordheim tunneling
for the thick and thin Al<sub>2</sub>O<sub>3</sub> RRAMs, respectively.
Finally, the variation control in device forming, SET voltage distribution,
high resistance state, low resistance state, and resistance ratio
is achieved with the TiO<sub><i>x</i></sub>/Al<sub>2</sub>O<sub>3</sub> bilayer RRAM devices by interfacial band engineering
with an ultrathin Al<sub>2</sub>O<sub>3</sub> dielectric material
