Highly Stable Artificial Synapse Consisting of Low-Surface Defect van der Waals and Self-Assembled Materials

The long-term plasticity of biological synapses was successfully emulated in an artificial synapse fabricated by combining low-surface defect van der Waals (vdW) and self-assembled (SA) materials. The synaptic operation could be achieved by facilitating hole trapping and releasing only via the amine (NH₂) functional groups in 3-aminopropyltriethoxysilane, which consequently induced a gradual conductance change in the WSe₂ channel. The vdW-SA synaptic device exhibited extremely stable long-term potentiation/depression (LTP/LTD) characteristics; its dynamic range and nonlinearity reproduced near 100 and 3.13/-6.53 (for LTP/LTD) with relative standard deviations (RSDs) below 2%. Furthermore, after conducting training and recognition tasks for the Modified National Institute of Standard and Technology (MNIST) digit patterns, we verified that the maximum recognition rate was 78.3%, and especially, its RSD was as low as 0.32% over several training/recognition cycles. This study provides a background for future research on advanced artificial synapses based on vdW and organic materials.