MRS Meetings and Events


EQ11.04.03 2022 MRS Spring Meeting

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

When and Where

May 10, 2022
2:30pm - 2:45pm

Hawai'i Convention Center, Level 3, 318A



Vinod Sangwan1,Sonal Rangnekar1,Joohoon Kang1,Jie Gu1,Haihua Wang1,Mark Hersam1

Northwestern University1


Vinod Sangwan1,Sonal Rangnekar1,Joohoon Kang1,Jie Gu1,Haihua Wang1,Mark Hersam1

Northwestern University1
The paradigm of neuromorphic computing in hardware is becoming increasingly urgent due to the ubiquity of portable electronics and the Internet of Things (IoT) that acquire and process vast amounts of data. Neuromorphic computing also promises to dramatically reduce power consumption compared to conventional digital computing by providing non-volatile memory and threshold switches that can store and process data locally to overcome the von Neumann bottleneck. While first-order linear memory devices have been developed that can store weight matrices in a dot product machine, higher-order memristive switches are desired for <i>in-situ</i> data processing. In this context, two-dimensional (2D) materials are being explored for memristive applications due to tunable electrostatic coupling, novel neuromorphic functions, and ultrathin geometries that facilitate scaling [1-3]. Solution-processed 2D materials provide additional advantages for large-area, flexible, and printed neuromorphic circuits. However, the memristive switching mechanisms in solution-processed 2D materials are poorly understood. In particular, understanding charge transport in composite films of solution-processed 2D materials is complicated by heterogeneous morphologies, the interplay of multiple physical processes, and the inaccessibility of the active area in two-terminal vertical geometries.<br/><br/>This presentation will discuss thermally activated memristive switching mechanisms in percolating networks of diverse solution-processed 2D semiconductors including MoS<sub>2</sub>, ReS<sub>2</sub>, WS<sub>2</sub>, and InSe [5]. This threshold switching behavior is distinct from the widely reported non-volatile resistive behavior arising from electrochemically active metal filaments or related conductive filaments bridging the device channel. The mechanism underlying thermally activated memristive switching is elucidated by engineering large-area lateral memristors that allow the direct observation of filament formation using spatially resolved optical and chemical analyses and <i>in situ </i>thermal analysis. These devices show high switching ratios (up to 10<sup>3</sup>) at low global electric fields (≈4 kV cm<sup>−1</sup>) that is explained by a thermally assisted electrical discharge that preferentially occurs at the sharp edges of 2D nanosheets. X-ray photoelectron spectroscopy and infrared imaging show that the filaments consist of oxygen-deficient regions that get heated (&gt;115 °C) during switching. Using the insight gained from the thickness dependence of switching in lateral devices, vertical devices have been designed and demonstrated with operating voltages as low as 2 V. A novel electroforming scheme is employed to tune the operating voltage in voltage-controlled threshold switches and current-controlled negative differential resistance devices. Overall, this work establishes percolating networks of solution-processed 2D semiconductor nanoflakes as a platform for high-order non-dynamical devices for neuromorphic circuits and systems. <br/><b>References</b><br/> <br/>[1] V. K. Sangwan and M. C. Hersam, <i>Nature Nanotechnology</i>, 15, 517 (2020).<br/>[2] V. K. Sangwan, H.-S. Lee, H. Bergeron, I. Balla, M. E. Beck, K.-S. Chen, and M. C. Hersam, <i>Nature</i>, <b>554</b>, 500-504 (2018).<br/>[3] H.-S. Lee, V. K. Sangwan, H. Bergeron, H. Y. Jeong, K. Su, and M. C. Hersam, <i>Advanced Functional Materials</i> 30, 2003683 (2020).<br/>[4] M. E. Beck and M. C. Hersam, <i>ACS Nano</i>, 14, 6498 (2020).<br/>[5] V. K. Sangwan, S. V. Rangnekar, J. Kang, J. Shen, H.-S. Lee, D. Lam, J. Shen, X. Liu, A. C. M. de Moraes, L. Kuo, J. Gu, H. Wang, and M. C. Hersam, <i>Advanced Functional Materials</i> DOI:10.1002/adfm.202107385 (2021).


2D materials | electrical properties

Symposium Organizers

Yoeri van de Burgt, Technische Universiteit Eindhoven
Yiyang Li, University of Michigan
Francesca Santoro, Forschungszentrum Jülich/RWTH Aachen University
Ilia Valov, Research Center Juelich

Symposium Support

Nextron Corporation

Publishing Alliance

MRS publishes with Springer Nature