Laser‐Induced Oxygen Engineering for Localized Homojunction Formation in SnS 2 Photodetectors

ABSTRACT The development of high‐performance optoelectronic devices based on 2D materials has attracted significant attention. However, conventional vertical stacking methods are limited by complex processes and interfacial defects. To overcome these challenges, we propose a simple and efficient one‐step process to form an in‐plane homojunction within a single n‐type tin disulfide (SnS 2 ) flake via direct laser irradiation. The core process, oxidative thinning, utilizes a focused 532 nm laser to locally convert a portion of SnS 2 into tin oxide (SnO x ). Consequently, an energy barrier arising from a work‐function difference of approximately 0.7 eV is formed at the interface, promoting the separation of photogenerated electron‐hole pairs. The fabricated photodetector demonstrates a fast response time (τ r /τ f = 474/299 ms), an improvement of several tens of times compared with the pristine SnS 2 device. Furthermore, it exhibits a high responsivity (R) of 703 mA W −1 , an external quantum efficiency (EQE) of 170%, and a remarkable specific detectivity (D * ) of 2.35 × 10 14 Jones, along with excellent operational stability. This laser‐induced local conversion technique presented can provide a powerful and practical platform for developing next‐generation flexible and wearable optoelectronic devices.