Enhancement of data storage capability in a bilayer oxide-based memristor for wearable electronic applications

In this work, a ZnO/NiO bilayer architecture is introduced to fabricate a transparent and flexible resistive random access memory device (Cu/ZnO/NiO/ITO) on polyethylene terephthalate substrate. The device exhibits excellent resistive switching (RS) characteristics, such as forming-free characteristic, low operating voltages, outstanding uniformity, long retention time (>10(4) s), high ON/OFF current ratio similar to 10(3), reliable multilevel cell characteristics and excellent mechanical flexibility. The multilevel properties have been systematically evaluated by varying the compliance current and tuning the stopping voltage, which shows that the whole resistance state is distinguishable and remained stable without any considerable deprivation over 10(3) s. Intrinsic tailoring of RS mechanism has been well explained in the framework of electric field-induced formation and rupture of the reproducible Cu filaments in ZnO/NiO layer. Furthermore, the metallic nature of conducting filament has been confirmed by temperature-dependent variation of the high- and low-resistance states. Due to the increasing demand for flexible electronics, the mechanical robustness of the proposed device has been examined by varying the bending time and radius. The present RS device shows potential towards integration in many transparent, flexible and high-density storage devices, such as electronic skins and flexible displays.