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WO3/WS2 core/shell nanowires were synthesized using a scalable fabrication method by combining wet chemical etching and chemical vapor deposition (CVD). Initially, WO3 nanowires were formed through wet chemical etching using a potassium hydroxide (KOH) solution, followed by oxidation at 650 °C. These WO3 nanowires were then sulfurized at 900 °C to form a WS2 shell, resulting in WO3/WS2 core/shell nanowires with diameters ranging from 90 to 370 nm. The synthesized nanowires were characterized using scanning electron microscopy (SEM), Raman, energy-dispersive X-ray spectroscopy (EDS), X-ray diffractometry (XRD), and transmission electron microscopy (TEM). The shell is composed of 2D WS2 layers with uniformly spaced 2D layers as well as the atomically sharp core/shell interface of WO3/WS2. Notably, the WO3/WS2 heterostructure nanowires exhibited a unique negative photoresponse under visible light (405 nm) illumination. This negative photoresponse highlights the importance of interface engineering in these heterostructures and demonstrates the potential of WO3/WS2 core/shell nanowires for applications in photodetectors and other optoelectronic devices. 

Abstract The prevailing von Neumann bottleneck has demanded alternatives capable of more efficiently executing massive data in state‐of‐the‐art digital technologies. Mimicking the human brain's operational principles, various artificial synapse devices have emerged, whose fabrications generally require high‐temperature complementary metal‐oxide‐semiconductor (CMOS) processes. Herein, centimeter‐scale tellurium (Te) films‐based optoelectronic synaptic devices are explored by a back‐end‐of‐line (BEOL) compatible low‐temperature (200 °C) chemical vapor deposition (CVD). The CVD‐grown Te films exhibit prominent semiconducting properties such as broadband photo‐responsiveness accompanying a large degree of mechanical deformability. These characteristics coupled with their scalable manufacturability realize a comprehensive set of optically‐stimulated synaptic plasticity; i.e., excitatory postsynaptic current (EPSC), paired‐pulse facilitation (PPF), and short‐to‐long‐term memory conversion, all of which are well preserved even under severe mechanical deformations. A variety of proof‐of‐concept applications for artificial neural networks (ANNs) are demonstrated employing these deformation‐invariant synaptic features; i.e., high‐accuracy (≈90%) pattern recognition, associative learning, and machine learning‐implemented visual perception. The fundamental mechanism for the synaptic operations is discussed in the context of their persistent photoconductivity (PPC) and its associated memory effect. This study highlights high promise of low‐temperature processable semiconductors for emergent neuromorphic architectures with various form factors beyond the conventional CMOS strategy.