Operando X-ray Microscopy of Memristive Devices

Orateur : Dillon D. FONG (Staff Scientist - Materials Science Division, Argonne National Laboratory)

Memristive devices are an emerging technology that enables both rich interdisciplinary science and novel device functionalities, such as non-volatile memories and nanoionics-based synaptic electronics. Recent work has shown that the reproducibility and variability of the devices depend sensitively on the defect structures created during electroforming as well as their continued evolution under dynamic electric fields. However, a fundamental principle guiding the material design of defect structures is still lacking, due to the difficulty in understanding dynamic defect behavior under different resistance states. Here we study the existence of threshold behavior by investigating model, single-crystal devices : resistive switching requires that the pristine oxygen vacancy concentration reside near a critical value. Theoretical calculations show that the threshold oxygen vacancy concentration lies at the boundary for both electronic and atomic phase transitions. Through operando, multimodal X-ray imaging, we show that field tuning of the local oxygen vacancy concentration below or above the threshold value is responsible for switching between different electrical states.

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