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.