(Invited) Multi-Level Non-Volatile Memory in Au/Monolayer MoS₂/Au Structures

The wide range of electronic and optical properties exhibited by two dimensional semiconductors, and their variation physical thickness, opens up new possibilities to create ultra-short length transistors [1], steep-slope switches [2, 3], light detecting/emitting devices [4, 5] and chemical/physical sensors. Recently, it was demonstrated that monolayer 2D semiconductors can also display resistive switching [6]. In this work we demonstrate that a single layer of large area CVD-grown moly disulphide (MoS2) sandwiched between two metal electrodes can be tuned to exhibit multi-level non-volatile resistive memory, with resistance values separated by 5 orders of magnitude. The switching process is unipolar and thermochemically driven (TCM memory) requiring significant Joule heating in the RESET process. Temperature dependent electrical measurements will be presented which demonstrate the charge transport mechanism varies between the initial state (IS), the high resistive state (HRS) and low resistive state (LRS). The temperature dependent behavior of the SET, RESET process is consistent with the creation and passivation of sulfur vacancies in the MoS2 monolayer. Conductive AFM measurements confirm that the multi-filamentary resistive memory effects are inherent to a single crystalline MoS2 triangle and not necessarily dependent of grain boundaries. This work demonstrates that potential for 2 terminal, multi-state, resistive memories for next generation digital memory and neuromorphic applications. [1] S. B. Desai et al., "MoS2 transistors with 1-nanometer gate lengths," Science, vol. 354, no. 6308, pp. 99-102, 2016. [2] S. Bhattacharjee, K. L. Ganapathi, S. Mohan, and N. Bhat, "A sub-thermionic MoS2 FET with tunable transport," Applied Physics Letters, vol. 111, no. 16, p. 163501, 2017. [3] D. Sarkar et al., "A subthermionic tunnel field-effect transistor with an atomically thin channel," Nature, vol. 526, no. 7571, p. 91, 2015. [4] K. Roy et al., "Graphene–MoS 2 hybrid structures for multifunctional photoresponsive memory devices," Nature nanotechnology, vol. 8, no. 11, p. 826, 2013. [5] X. Zhou et al., "2D Layered Material‐Based van der Waals Heterostructures for Optoelectronics," Advanced Functional Materials, vol. 28, no. 14, p. 1706587, 2018. [6] R. Ge et al., "Atomristor: Nonvolatile Resistance Switching in Atomic Sheets of Transition Metal Dichalcogenides," Nano letters, vol. 18, no. 1, pp. 434-441, 2017.