Oxygen annealing effect on resistive switching characteristics of multilayer CeO₂/Al/CeO₂ resistive random-access memory

Abstract

Cerium oxide-based memristors have been extensively studied because of their compatibility with CMOS technology. Yet, inconsistency of resistive switching parameters is one of the main contests in development of nonvolatile memory for commercialization. Owing to filamentary nature of the resistive switching devices, variability of the resistive switching characteristics can be reduced by doping, where conductive filaments can easily grow due to reduction in the formation energy of oxygen vacancies. In this work, multilayer CeO 2 /Al/CeO 2 films were prepared through radiofrequency (rf) sputtering at room temperature to study the effect of oxygen annealing on the resistive switching characteristics. Device with CeO 2 /Al/CeO 2 multilayer structure after annealing exhibits reduction of defects and improved switching endurance, good data retention, and uniformity in operational parameters. The resistive switching characteristics have been simulated using space charge limited conduction and Schottky emission at high field region of the high resistance state, which is well fitted by linear curve fitting analysis. Improvement in the switching characteristics revealed that Al charge trapping layer has diffused into the CeO 2 matrix, which might have resulted in lower density of oxygen vacancies due to oxygen annealing. Experimental I-V analysis indicate that oxygen annealing is an effective approach to enhance the switching characteristics of RRAM devices.

Comprehensive Model of Electron Conduction in Oxide-Based Memristive Devices

“…Hence, an alternative conduction mechanism with nonexponential voltage dependence is required. Such a characteristic is found in the space-charge limited current (SCLC) model, which is frequently used to explain the transport in VCM cells. ,,− …”

“…To verify this type of conduction, the I–V dependence is measured and plotted on a double logarithmic scale, which allows determination of the power law I ∝ V α by a linear regression. ,,− An example from the work of Maikap of this approach is shown in Figure for a W/TaO x /TiN cell. The slopes α determined in resistive switching devices differ strongly, and the values in the referenced literature are found between 0.8 and 21. , …”

Density functional theory insight into metal ions and vacancies for improved performance in storage devices

“…In this case, the formation of CFs will not be dispersed throughout the doped composite for RS material used between electrodes in RRAM devices. This will reduce the variability 11 and improve the RS behavior of ATiO 3. 55 Previous studies reported the role of formation and rupturing of CFs in controlling the RS behavior 56,57 .…”

“…A significant increasing factor of RRAM is its simple structure of RRAM exhibiting better RS behavior because of long retention, low power consumption, small size, and high‐density integration 6‐10 . Inherently low voltage (<2 V) 11 and power consumption of RRAM leverage them in the industry of energy saving devices 2,12‐14 . The review of Chakraborty et al was focused on low energy aspect of NVM and their application in energy efficient memory and computing devices 15 .…”

Improved resistive switching characteristics of a multi-stacked HfO2/Al2O3/HfO2 RRAM structure for neuromorphic and synaptic applications: experimental and computational study

“…6 . Such types of variations have been noticed in many RRAM devices such as Pt/Ti/CeO 2 /Al/CeO 2 /Pt 48 and particularly in devices with TaN as top electrode like TaN/CeO 2 /Al/CeO 2 /Pt 49 and TaN/CeO 2 /Ti/CeO 2 /Pt 50 devices. Such behavior causes variations in HRS/LRS ratio from device to device.…”