Ag nanoparticles modified large area monolayer MoS₂ phototransistors with high responsivity

Monolayer MoS₂ is considered to be one of the best candidates for next generation electronics because of its ultra-thin body and direct band gap. However, MoS₂ based transistors have relatively low photoresponsivity, field effect mobility and narrow response spectrum range, which hinder the application of MoS₂ in optoelectronic devices. Here, based on the enhancement of localized surface plasmon resonance (LSPR), a simple method of depositing Ag nanoparticles on the MoS₂ surface is used. By adjusting the size of Ag nanoparticles, the response spectral range of phototransistor is broadened from red to near ultra-violet. The photoresponsivity gains an increase of 470% up to 2.97 × 10⁴ A W^-1 at 610 nm, and the response time also shows a decrease to some extent. The enhanced responsivity is comparable to those of devices encapsulated with high-quality dielectrics, and superior over other reported monolayer MoS₂ in ambient conditions. The high responsivity and working current enables a wide range of device applications. This work provides a viable route towards performance enhancement of two-dimensional phototransistors.