Cu‐Plasma‐Induced Interfacial Engineering for Nanosecond Scale WS ₂ /CuO Heterojunction Photodetectors

Abstract Heterojunction photodetectors (PDs) with ultrafast response speeds are urgently required for applications in fields such as optical communication and automated production. However, the low separation efficiency of photogenerated carriers owing to interfacial effects (including interfacial defects and barriers) limits the response speed to the order of seconds to milliseconds. Herein, for the first time, an interface‐engineered heterostructure is designed with a gradient band alignment to obtain a response speed on the nanosecond scale, where the separation efficiency of the photogenerated carriers is enhanced by Cu‐plasmon‐induced charge transfer. Cu nanoparticles (NPs) are implanted into the heterojunctions with two different structures: WS 2 /CuO@Cu and WS 2 @Cu/CuO. Devices with Cu NPs implanted at the interface exhibit an excellent detectivity of 5 × 10 12 Jones and a high responsivity of 979 A W −1 . More importantly, an ultrafast response speed of 24 ns is achieved, making it one of the fastest PDs in the field of plasmonic PDs. This high performance is attributed to Cu‐plasmon‐induced interface engineering, which is confirmed by experiments and theoretical calculations. The interface engineering method proposed in this study provides a new approach for achieving ultrafast PDs.