Highly Localized Strain in a MoS2/Au Heterostructure Revealed by Tip-Enhanced Raman Spectroscopy

Mahfujur Rahaman, Raul D. Rodriguez, Gerd Plechinger, Stefan Moras, Christian Schüller, Tobias Korn, Dietrich R.T. Zahn

Research output: Contribution to journalArticle

38 Citations (Scopus)

Abstract

Tip-enhanced Raman spectroscopy (TERS) has been rapidly improved over the past decade and opened up opportunities to study phonon properties of materials at the nanometer scale. In this Letter, we report on TERS of an ultrathin MoS2 flake on a nanostructured Au on silicon surface forming a two-dimensional (2D) crystal/plasmonic heterostructure. Au nanostructures (shaped in triangles) are prepared by nanosphere lithography, and then MoS2 is mechanically exfoliated on top of them. The TERS spectra acquired under resonance conditions at 638 nm excitation wavelength evidence strain changes spatially localized to regions as small as 25 nm in TERS imaging. We observe the highest Raman intensity enhancement for MoS2 on top of Au nanotriangles due to the strong electromagnetic confinement between the tip and a single triangle. Our results enable us to determine the local strain in MoS2 induced during heterostructure formation. The maximum frequency shift of E2g mode is determined to be (4.2 ± 0.8) cm-1, corresponding to 1.4% of biaxial strain induced in the MoS2 layer. We find that the regions of maximum local strain correspond to the regions of maximum topographic curvature as extracted from atomic force microscopy measurements. This tip-enhanced Raman spectroscopy study allows us to determine the built-in strain that arises when 2D materials interact with other nanostructures.

Original languageEnglish
Pages (from-to)6027-6033
Number of pages7
JournalNano Letters
Volume17
Issue number10
DOIs
Publication statusPublished - 11 Oct 2017

Keywords

  • MoS
  • plasmonics
  • strain
  • Tip-enhanced Raman spectroscopy (TERS)
  • transition metal dichalcogenides (TMDC)
  • two-dimensional materials

ASJC Scopus subject areas

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

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