Visualizing Thermally Activated Memristive Switching in Percolating Networks of Solution‐Processed 2D Semiconductors

• Published in: Advanced functional materials 2021-12, Vol.31 (52), p.n/a
• Main Authors: Sangwan, Vinod K., Rangnekar, Sonal V., Kang, Joohoon, Shen, Jianan, Lee, Hong‐Sub, Lam, David, Shen, Junhua, Liu, Xiaolong, Moraes, Ana C. M., Kuo, Lidia, Gu, Jie, Wang, Haihua, Hersam, Mark C.
• Format: Article
• Language: English
• Subjects: Biomimetics; Dendritic structure; Electric discharges; in situ imaging; liquid phase exfoliation; Materials science; Memory devices; memristor; Memristors; Nanosheets; Networks; Neuromorphic computing; Percolation; Semiconductors; Switching; Two dimensional materials; van der Waals materials
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.202107385

Memristive systems present a low‐power alternative to silicon‐based electronics for neuromorphic and in‐memory computation. 2D materials have been increasingly explored for memristive applications due to their novel biomimetic functions, ultrathin geometry for ultimate scaling limits, and potential for fabricating large‐area, flexible, and printed neuromorphic devices. While the switching mechanism in memristors based on single 2D nanosheets is similar to conventional oxide memristors, the switching mechanism in nanosheet composite films is complicated by the interplay of multiple physical processes and the inaccessibility of the active area in a two‐terminal vertical geometry. Here, the authors report thermally activated memristors fabricated from percolating networks of diverse solution‐processed 2D semiconductors including MoS2, ReS2, WS2, and InSe. The mechanisms underlying threshold switching and negative differential resistance are elucidated by designing large‐area lateral memristors that allow the direct observation of filament and dendrite formation using in situ spatially resolved optical, chemical, and thermal analyses. The high switching ratios (up to 103) that are achieved at low fields (≈4 kV cm−1) are explained by thermally assisted electrical discharge that preferentially occurs at the sharp edges of 2D nanosheets. Overall, this work establishes percolating networks of solution‐processed 2D semiconductors as a platform for neuromorphic architectures. In situ visualization and chemical analysis of memristive devices based on solution‐processed 2D semiconductors reveal switching mechanisms and filament formation. Intrinsic resistive switching in percolating films originates from thermally activated electrical discharge at nanosheet edges, resulting in characteristics that are promising for artificial neurons in neuromorphic computing.