Local photodoping in monolayer MoS2

TL;DR

This paper investigates how laser-induced photodoping locally affects photocurrent in monolayer MoS2 transistors, revealing the role of substrate interfaces and electronic state filling in modulating optoelectronic behavior.

Contribution

It provides the first detailed local analysis of photodoping effects in MoS2 transistors using scanning photocurrent microscopy, highlighting the importance of gate-insulator interfaces.

Findings

Photodoping fills electronic states, reducing photocurrent generation.

The gate-insulator interface is crucial for persistent photodoping effects.

Photodoping can be controlled locally, impacting device design.

Abstract

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.