Investigation of the Eightwise Switching Mechanism and Its Suppression in SrTiO₃ Modulated by Humidity and Interchanged Top and Bottom Platinum and LaNiO₃ Electrode Contacts

Memristive devices are hardware components for applications in neuromorphic computing, memories, and logic computation. This work contributes to the ongoing debate on the switching mechanism of eightwise polarity in SrTiO₃-based resistive switches. Specifically the effect of atmospheric humidity on the materials defect chemistry and switching properties is considered. Asymmetric devices are designed by exchanging the top and bottom positions of Pt and LaNiO₃ electrodes allowing for a separate analysis of the top and the bottom metal-oxide interfaces. Under dry atmospheres the switching hysteresis is enhanced with a top Pt contact and suppressed with a bottom Pt contact. It is argued that the buried position and dense microstructure of the bottom platinum impedes an oxygen vacancy driven switching mechanism. Under humid atmospheres eightwise switching occurs in both devices suggesting the presence of two switching mechanisms within the same eightwise switching polarity, namely, oxygen vacancy and hydroxide ion enabled switching. The findings help develop strategies to suppress eightwise switching by burying the active metal-oxide interface and ensuring dense electrode microstructures. Suppression of switching mechanisms relying on exchange with the environment is desirable for technological implementation of resistive switches and for strategies in stacking of memristive devices for memory and for neuromorphic hardware.