Local photodoping in monolayer MoS₂

Inducing electrostatic doping in 2D materials by laser exposure (photodoping effect) is an exciting route to tune optoelectronic phenomena. However, there is a lack of investigation concerning in what respect the action of photodoping in optoelectronic devices is local. Here, we employ scanning photocurrent microscopy (SPCM) techniques to investigate how a permanent photodoping modulates the photocurrent generation in MoS₂ transistors locally. We claim that the photodoping fills the electronic states in MoS₂ conduction band, preventing the photon-absorption and the photocurrent generation by the MoS₂ sheet. Moreover, by comparing the persistent photocurrent (PPC) generation of MoS₂ on top of different substrates, we elucidate that the interface between the material used for the gate and the insulator (gate-insulator interface) is essential for the photodoping generation. Our work gives a step forward to the understanding of the photodoping effect in MoS₂ transistors and the implementation of such an effect in integrated devices. (paper)