Coexistence of bipolar and unipolar resistive switching behaviors in the double-layer Ag/ZnS-Ag/CuAlO2/Pt memory device

The schematic diagrams of the resistive switching (RS) mechanism with the different compliance current (CC). The formation and rupture of Ag-CFs in the CuAlO2 layer should be accepted as the BRS behavior under the low CC of 1 mA, as shown in (a) and (b). A following transformation (“forming”) process is necessary to realize the BRS-to-URS transformation, as shown in (c) and (d). Afterward, the formation and rupture of Cu-vacancy-CFs are responsible for the URS behavior in the case of high CC (10 mA), as shown in (e) and (f).