Abstract: The development of artificial photosensitive synapses with high sensitivity and biomimetic properties that combine innovative concepts and neuromorphic architectures is crucial to achieving highly integrated and flexible intelligent visual systems. Recently, graphene heterostructure-based photosensitive synaptic transistors have been extensively studied for this purpose. However, compared to traditional transistors, vertical structure thin film transistors (VTFTs) with ultra-short channels and advantages, such as high integration, have yet to be investigated in photosensitive synapses. Here, we report an ultra-thin VTFT featuring a graphene/W_xSe_x-1 van der Waals heterostructure that combines photonic and neuromorphic elements. We demonstrate a VTFT in which the channel layer is formed by covalently bonded W_xSe_x-1 nanomaterials produced by introducing Se atoms on the surface of a tungsten metal thin film deposited via radio-frequency sputtering. This structure successfully simulated the main synaptic function, exhibited photosensitive synaptic responses to ultraviolet (λ = 365 nm) light, and demonstrated highly reliable electrical performance. Furthermore, the incorporation of gold nanoparticles changed the photosensitive synaptic response properties of the graphene/W_xSe_x-1 heterostructure from excitatory to inhibitory, showing a responsivity of about ∼14 A W^-1, which was attributed to the heterojunction interface resonant effects and efficient charge transfer induced by localized surface plasmons. This further enabled optical artificial synaptic applications while operating with low voltage spikes and low light intensity. This work provides a novel strategy for integrating and developing biological and nano-electronic systems.

Key words: Ultra-thin, Vertical TFT, Au nanoparticles, Photo sensor, Photo responsivity, Photo synapse