Point Defects and Grain Boundaries in Rotationally Commensurate MoS2 on Epitaxial Graphene

Xiaolong Liu, Itamar Balla, Hadallia Bergeron, Mark C Hersam

Research output: Contribution to journalArticle

63 Citations (Scopus)

Abstract

With reduced degrees of freedom, structural defects are expected to play a greater role in two-dimensional materials in comparison to their bulk counterparts. In particular, mechanical strength, electronic properties, and chemical reactivity are strongly affected by crystal imperfections in the atomically thin limit. Here, ultrahigh vacuum (UHV) scanning tunneling microscopy (STM) and spectroscopy (STS) are employed to interrogate point and line defects in monolayer MoS2 grown on epitaxial graphene (EG) at the atomic scale. Five types of point defects are observed with the majority species showing apparent structures that are consistent with vacancy and interstitial models. The total defect density is observed to be lower than MoS2 grown on other substrates and is likely attributed to the van der Waals epitaxy of MoS2 on EG. Grain boundaries (GBs) with 30° and 60° tilt angles resulting from the rotational commensurability of MoS2 on EG are more easily resolved by STM than atomic force microscopy at similar scales due to the enhanced contrast from their distinct electronic states. For example, band gap reduction to ∼0.8 and ∼0.5 eV is observed with STS for 30° and 60° GBs, respectively. In addition, atomic resolution STM images of these GBs are found to agree well with proposed structure models. This work offers quantitative insight into the structure and properties of common defects in MoS2 and suggests pathways for tailoring the performance of MoS2/graphene heterostructures via defect engineering.

Original languageEnglish
Pages (from-to)20798-20805
Number of pages8
JournalJournal of Physical Chemistry C
Volume120
Issue number37
DOIs
Publication statusPublished - Sep 22 2016

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Energy(all)
  • Surfaces, Coatings and Films
  • Physical and Theoretical Chemistry

Fingerprint Dive into the research topics of 'Point Defects and Grain Boundaries in Rotationally Commensurate MoS<sub>2</sub> on Epitaxial Graphene'. Together they form a unique fingerprint.

  • Cite this