Design of Oxygen Vacancy Configuration for Memristive Systems

Abstract

Oxide-based valence-change memristors are promising nonvolatile memories for future electronics that operate on valence-change reactions to modulate their electrical resistance. The memristance is associated with the movement of oxygen ionic carriers through oxygen vacancies at high electric field strength via structural defect modifications that are still poorly understood. This study employs a CeGdO solid solution model to probe the role of oxygen vacancies either set as "free" or as "immobile and clustered" for the resistive switching performance. The experiments, together with the defect chemical model, show that when the vacancies are set as "free", a maximum in memristance is found for 20 mol % of GdO doping, which clearly coincides with the maximum in ionic conductivity. In contrast, for higher gadolinia concentration, the oxide exhibits only minor memristance, which originates from the decrease in structural symmetry, leading to the formation of "immobile" oxygen defect clusters, thereby reducing the density of mobile ionic carriers available for resistive switching. The research demonstrates guidelines for engineering of the oxide's solid solution series to set the configuration of its oxygen vacancy defects and their mobility to tune the resistive switching for nonvolatile memory and logic applications.

Dynamic Current–Voltage Analysis of Oxygen Vacancy Mobility in Praseodymium‐Doped Ceria over Wide Temperature Limits

“…The method was previously successfully applied in measuring oxygen vacancy mobilities in reduced molybdenum trioxide thin films at near ambient temperatures . Here, we use the dynamic I–V analysis to measure oxygen vacancy mobilities in ten percent praseodymium‐doped ceria, Pr 0.1 Ce 0.9 O 2− δ (PCO), MIEC thin films of interest as a cathode model material in SOFCs at elevated temperatures and for room temperatures nanoelectronic applications . Models for oxygen vacancy formation and transport in PCO are reviewed in Appendix .…”

“…This is technologically relevant as it shows that extrapolation of MIEC ionic transport coefficients to low temperatures applicable to, e.g., memristive devices operated at room temperature, utilizing out‐of‐equilibrium quenched MIEC materials, is justified. We demonstrated that the dynamic I–V analysis can be applied to crossbar devices, the same configuration used for implementation and study of memristive devices …”

“…[24] Here, we use the dynamic I-V analysis to measure oxygen vacancy mobilities in ten percent praseodymium-doped ceria, Pr 0.1 Ce 0.9 O 2−δ (PCO), MIEC thin films of interest as a cathode model material in SOFCs at elevated temperatures [4,25] and for room temperatures nanoelectronic applications. [26] Models for oxygen vacancy formation and transport in PCO [25] are reviewed in Appendix B. We demonstrate that the method is applicable over wide temperature limits, and more importantly, for accurate determination of activation energies over a wide…”

Lithium‐Battery Anode Gains Additional Functionality for Neuromorphic Computing through Metal–Insulator Phase Separation

“…The largest two categories of memristive devices—valence change memories and electrochemical metallization memories—rely on creation, annihilation, and motion of ions and defects through ionic conductors under a bias (which is used to control resistive state). Valence change memories are based on transition metal oxides whose resistive state depends on the redistribution of bulk O 2– and O 2– vacancies under bias (and resulting reduced metal cations) . Typical diffusivity values for state‐of‐the‐art switching oxides (SrTiO 3 , TiO 2 and TaO x ) are 10 −15 –10 −13 cm 2 s −1 at ambient temperature.…”

Fabricating Nitrogen‐Rich Fe−N/C Electrocatalysts through CeO2‐Assisted Pyrolysis for Enhanced Oxygen Reduction Reaction

“…Interestingly, as a widely‐recognized rare earth oxide, cerium oxide (CeO 2 ) has a unique oxygen storage and release capacity, prominent reversible redox property (Ce 3+ /Ce 4+ ) and possesses a large number of oxygen vacancies, which are beneficial to ORR catalytic processes . Especially, CeO 2 is possible to stabilize more nitrogen sources during catalyst synthesis process .…”