Research on switching property of an oxide/copper sulfide hybrid memory

Resistive random access memory (ReRAM) has drawn lots of attention for nonvolatile memories. Among various resistive switching materials and phenomena, solid state electrolytes, such as copper sulfide and Ag-Ge-Se devices, show interesting properties for memory or logic application. But too small turn on voltage (V_set is below 0.3 V) could be positive in point of power consumption but should be improved considering disturbance by other signals and V_set variation for stable read operation. So we report a novel double layered hybrid structure composed of a copper sulfide layer and a thin oxide (Cu_xO and SiO₂). Switching mechanism of these devices could be the formation and rupture of conductive copper bridge. Cu_xS/SiO₂ device exhibits large on/off ratio over 10⁷ at -0.2 V_read and multi-level possibility through strong dependence of on-state resistance on programming current. In addition, V_set was improved to be about 1V and off-state resistance was increased up to G¿.