Resistive switching in polyvinylpyrrolidone/molybdenum disulfide composite-based memory devices

Four types of resistive random access memory structures with an active layer comprising: (1) MoS₂ (device A), (2) PVP (device B), (3) PVP and MoS₂ bilayer (device C), and (4) PVP + MoS₂ nanocomposites with 10 (device D), 20 (device E), 30 (device F) and 40 wt% (device G) MoS₂, have been fabricated with Al and Ag as bottom and top electrodes, respectively. A study of resistive switching and electrical conduction mechanisms of these resistive random access memory modules revealed that devices A and B did not exhibit switching characteristics. Device C showed a combination of bipolar and threshold switching with a low switching voltage of 0.40 V. Device G portrayed bipolar switching at 0.56 V. In device C, space charge-limited conduction with a transition voltage Vtr = 0.24 V was observed, whereas in device G, Ohmic behaviour between 0.0 and 0.22 V, followed by trapping of charge in the 0.22-0.56 V regime before switching, was noticed. Both devices C and G showed a reasonable (≥ 10²) ON/OFF ratio. In nanocomposite devices, an increase in MoS₂ content resulted in an increase in electrical conductivity in the Ohmic region, leading to threshold switching at 30 wt% (device F) and ultimately bipolar switching at 40 wt% (device G). These studies have shown that both switching and conduction mechanisms are sensitive to the type and composition of the active layer in the devices studied.