In-situ formation and evolution of atomic defects in monolayer WSe2 under electron irradiation

Robert Leiter,Ute Kaiser,Yueliang Li

doi:10.1088/1361-6528/abb335

Abstract

Transition metal dichalcogenide (TMD) monolayers such as MoS2, MoSe2, MoTe2, WS2 and WSe2 have attracted significant interest due to their remarkable electronic and optical properties, exhibiting a direct band gap, enabling usability in electronics and optics. Their properties can be altered further by the introduction of lattice defects. In this work, the dynamics of the formation of electron-beam-induced lattice defects in monolayer WSe2 are investigated by in-situ spherical and chromatic aberration-corrected low-voltage transmission electron microscopy. We show and analyze the electron-dose-limited life of a monolayer WSe2 from the formation of isolated Se vacancies over extended defects such as vacancy lines, mirror twin boundaries (MTBs) and inversion domains towards the loss of W atoms leading to the formation of holes and finally the destruction of the monolayer. We identify, moreover, a new type of MTB. Our study extends the basic understanding of defect dynamics in monolayer WSe2, sheds further light on the electron radiation response and suggests new ways for engineering the in-plane architecture of TMDs.

Highlights

After the discovery of graphene, two-dimensional transition metal dichalcogenides (2D-Transition metal dichalcogenide (TMD)) have received increasing attention
We report the formation and evolution of defects in monolayer WSe2 at room temperature, including all three types of mirror twin boundaries (MTBs) as well as a fourth type, which was not observed in TMDs so far
We start our discussion with presenting the monolayer flake of WSe2 used for transmission electron microscope (TEM) investigation, which is denoted by the white arrow in figure 1(a), and the structural model in planand side view shown in figure 1(c)

Summary

Introduction

After the discovery of graphene, two-dimensional transition metal dichalcogenides (2D-TMDs) have received increasing attention. Members of the class of 2D-TMDs, tungsten diselenide (WSe2) is a very promising candidate with a wide range of optoelectronic applications [4,5,6,7,8,9,10]. It opens its direct bandgap from 1.2 eV in bulk [11] to 1.7 eV in the monolayer structure [12]. WSe2 can work as a saturable absorber for pulsed fiber lasers [14]

Methods

Results

Conclusion