Interlayer breathing and shear modes in few-trilayer MoS2and WSe2

Yanyuan Zhao, Xin Luo, Hai Li, Jun Zhang, Paulo T. Araujo, Chee Kwan Gan, Jumiati Wu, Hua Zhang, Su Ying Quek, Mildred S. Dresselhaus, Qihua Xiong

Research output: Journal article publicationJournal articleAcademic researchpeer-review

444 Citations (Scopus)

Abstract

Two-dimensional (2D) layered transition metal dichalcogenides (TMDs) have recently attracted tremendous interest as potential valleytronic and nanoelectronic materials, in addition to being well-known as excellent lubricants in the bulk. The interlayer van der Waals (vdW) coupling and low-frequency phonon modes and how they evolve with the number of layers are important for both the mechanical and the electrical properties of 2D TMDs. Here we uncover the ultralow frequency interlayer breathing and shear modes in few-layer MoS2and WSe2, prototypical layered TMDs, using both Raman spectroscopy and first principles calculations. Remarkably, the frequencies of these modes can be perfectly described using a simple linear chain model with only nearest-neighbor interactions. We show that the derived in-plane (shear) and out-of-plane (breathing) force constants from experiment remain the same from two-layer 2D crystals to the bulk materials, suggesting that the nanoscale interlayer frictional characteristics of these excellent lubricants should be independent of the number of layers.
Original languageEnglish
Pages (from-to)1007-1015
Number of pages9
JournalNano Letters
Volume13
Issue number3
DOIs
Publication statusPublished - 13 Mar 2013
Externally publishedYes

Keywords

  • breathing modes
  • first principle calculations
  • linear chain model
  • Raman spectroscopy
  • shear modes
  • Transition metal dichalcogenides

ASJC Scopus subject areas

  • Bioengineering
  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanical Engineering

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