Unveiling Controlled Growth of Single‐Crystalline Layered Sb ₂ Te ₃ Via Van Der Waals Epitaxy for Visible‐Light Photodetectors and Optoelectronic Synapses

Abstract 2D layered Sb 2 Te 3 has emerged as a promising material for thermoelectric and optoelectronic applications. However, fabricating single‐crystalline Sb 2 Te 3 flakes with the desired size, shape, and orientation remains challenging due to limited understanding of their growth mechanisms. In this study, how the substrate, growth time, carrying gas, and its flow rate influence the growth behavior of Sb 2 Te 3 flakes through a chemical vapor deposition (CVD) approach combined with van der Waals epitaxy (vdWE) is elucidated. By fine‐tuning these growth parameters, Sb 2 Te 3 flakes with controlled size, morphology, and crystal orientation on mica substrates are successfully achieved. Notably, a record‐high anisotropy ratio in Sb 2 Te 3 flakes exceeding 10,000 is obtained. Photodetectors fabricated from these flakes demonstrate excellent optoelectronic performance, achieving a responsivity of 1.34 A W −1 , a large external quantum efficiency (EQE) of 332%, and a high external specific detectivity (D * ) of 1.38 × 10¹⁰ Jones under a light power density of 10 mW cm − 2 . Moreover, the device exhibits modulated photocurrent under pulsed light, suggesting potential applications in optoelectronic synapses. This work provides detailed insights into the controlled growth of single‐crystalline Sb 2 Te 3 flakes, offering unprecedented opportunities for exploring their fundamental properties in the development of next‐generation thermoelectric and optoelectronic devices.