Carrier transport and memory mechanisms of multilevel resistive memory devices with an intermediate state based on double-stacked organic/inorganic nanocomposites

• Multilevel resistive memory devices with an intermediate state based on organic/inorganic nanocomposites were fabricated.
• Devices were repeatedly operated in the three states, indicative of multilevel resistive memory devices.
• Reliable intermediate state was realized under positive and negative applied voltages.
• Differences in the three current states were clearly observed for up to 200 s.
• Three current states of the devices were maintained for retention times larger than 1 × 104 s.

Multilevel resistive memory devices with an intermediate state were fabricated utilizing a poly(methylmethacrylate) (PMMA) layer sandwiched between double-stacked PMMA layers containing CdSe/ZnS core–shell quantum dots (QDs). The current–voltage (I–V) curves on a Al/[PMMA:CdSe/ZnS QD]/PMMA/[PMMA:CdSe/ZnS QD]/indium-tin-oxide/glass device at low applied voltages showed current bistabilities with three states, indicative of multilevel characteristics. A reliable intermediate state was realized under positive and negative applied voltages. The carrier transport and the memory mechanisms of the devices were described on the basis of the I–V curves and energy band diagrams, respectively. The write-read-erase-read-erase-read sequence of the devices showed rewritable, nonvolatile, multilevel, and memory behaviors. The currents as functions of the retention time showed that three current states were maintained for retention times larger than 1 × 104 s, indicative of the good stability of the devices.

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