  We report a memristive switching effect in the Pt/CuOx/Si/Pt devices prepared
by rf sputtering technique at room temperature. Different from other Cu-based
switching systems, the devices show a non-filamentary switching effect. A
gradual electroforming marked by resistance increasing and capacitance
decreasing is observed in current-voltage and capacitance characteristics. By
the Auger electron spectroscopy analysis, a model based on Cu ion and oxygen
vacancy drift, and thickness change of the SiOx layer at the CuOx/Si interface
was proposed for the memristive switching and gradual electroforming,
respectively. The present work would be meaningful for the preparation of
forming-free and homogeneous memristive devices.
