Mechanism of Thermally Activated Memristive Switching in Percolating Networks of 2D Semiconductor Nanosheets

Brain-inspired computing hardware is emerging as a promising paradigm to dramatically reduce power consumption compared to conventional digital computing limited by the von Neumann bottleneck. Nanoscale devices such as non-volatile memristors and volatile dynamical switches are being explored as underlying building blocks for neuromorphic circuits. Memristors based on two-dimensional (2D) materials enable tunable electrostatic coupling, novel bio-realistic functions, large-area, flexible, and printed neuromorphic circuits [1-4]. However, the memristive switching mechanisms in 2D nanosheet composites are poorly understood. Here, we present thermally activated memristive switching mechanisms in percolating networks of diverse solution-processed 2D semiconductors including MoS₂, ReS₂, WS₂, and InSe [5]. The mechanism is elucidated by direct observation of channels using spatially resolved optical and chemical analyses (revealing oxygen-deficient filaments) and in situ thermal analysis (revealing local heating up to 115 °C). These devices show high switching ratios (up to 10³) at low global electric fields (≈4 kV cm⁻¹) that is explained by a thermally assisted electrical discharge that preferentially occurs at the sharp edges of 2D nanosheets. These results establish percolating networks of 2D nanosheets as an interesting materials system for high-order non-dynamical systems for neuromorphic circuits.  

References:

[1] V. K. Sangwan and M. C. Hersam, Nature Nanotechnology, 15, 517 (2020).

[2] V. K. Sangwan, H.-S. Lee, et al., Nature, 554, 500-504 (2018).

[3]  H.-S. Lee, V. K. Sangwan, et al., Advanced Functional Materials 30, 2003683 (2020).

[4] M. E. Beck and M. C. Hersam, ACS Nano, 14, 6498 (2020).

[5] V. K. Sangwan, S. V. Rangnekar, J. Kang, et al.,, Advanced Functional Materials DOI:10.1002/adfm.202107385 (2021).