The Atomic and Electronic Structure of 0° and 60° Grain Boundaries in MoS2

Terunobu Nakanishi,Osamu Takeuchi,Kota Murase,Yasumitsu Miyata,Hisanori Shinohara,Hidemi Shigekawa,Takashi Taniguchi,Yu Kobayashi,Kenji Watanabe,Ryo Kitaura,Shoji Yoshida

doi:10.3389/fphy.2019.00059

Abstract

We have investigated atomic and electronic structure of grain boundaries in monolayer MoS2, where relative angles between two different grains are 0 and 60 degree. The grain boundaries with specific relative angle have been formed with chemical vapor deposition growth on graphite and hexagonal boron nitride flakes; van der Waals interlayer interaction between MoS2 and the flakes restricts the relative angle. Through scanning tunneling microscopy and spectroscopy measurements, we have found that the perfectly stitched structure between two different grains of MoS2 was realized in the case of the 0 degree grain boundary. We also found that even with the perfectly stitched structure, valence band maximum and conduction band minimum shows significant blue shift, which probably arise from lattice strain at the boundary.

Highlights

A post-graphene material, transition metal dichalcogenide (TMD), has recently attracted a great deal of attention
We have focused on orientation-limited growth of a TMD and investigation of localized boundary states using scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS); the STS is a powerful tool to investigate domain boundaries [32, 33]
Electronic properties and defect densities in two types of grain boundaries (GBs) in MoS2 grown by the chemical vapor deposition (CVD) process were investigated

Summary

Introduction

A post-graphene material, transition metal dichalcogenide (TMD), has recently attracted a great deal of attention. TMDs have a long research history, but research on properties of monolayer TMDs, three-atom-thick atomic layers, has only recently been started [1,2,3]. One of the most distinct in TMDs from graphene is that TMDs can have sizable bandgap (∼2 eV), leading to electronic and optoelectronic applications of TMD atomic layers [4]. In conjunction with the flexibility arising from the ultrathin structure, flexible electronic and optoelectronic devices can be made [8, 9]. Monolayer TMDs in 2H form can have valley-degree-of-freedom, which may lead to future novel electronic devices based on valleytronics [10, 11]

Methods

Results

Conclusion