Evidence Of Electrochemical Resistive Switching In The Hydrated Alumina Layers Of Cu/Cutcnq/(Native Alox)/Al Junctions

We have investigated bipolar resistive switching of Cu/CuTCNQ/Al cross-junctions in both vacuum and different gas environments. While the generally observed S-shaped I-V hysteresis was reproduced in ambient air, it was reversibly suppressed in well-degassed samples in vacuum and in dry N-2. The OFF-switching currents in ambient air peaked when approximately +2.6V was applied to the Al electrode at low voltage sweep rates. OFF-switching at constant bias was accelerated in humid and oxygen-rich atmospheres. For unbiased samples stored in air, ON-state (R-ON) and OFF-state (R-OFF) resistances increased with time, and R-ON surpassed the initial R-OFF after approximately one week. Retention times were enhanced for samples stored in vacuum and those with a larger cross-junction area. We suggest that resistive switching occurs in a hydrated native alumina layer at the CuTCNQ/Al interface that grows in thickness during exposure to ambient humidity: ON-switching by electrochemical metallization of free Al and/or Cu ions and OFF-switching by anodic oxidation of the Al electrode and previously grown metal filaments. (C) 2013 AIP Publishing LLC.