Direct imaging of band profile in single layer MoS2 on graphite: Quasiparticle energy gap, metallic edge states, and edge band bending

Chendong Zhang, Amber Johnson, Chang Lung Hsu, Lain Jong Li, Chih Kang Shih*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

355 Scopus citations

Abstract

Using scanning tunneling microscopy and spectroscopy, we probe the electronic structures of single layer MoS2 on graphite. The apparent quasiparticle energy gap of single layer MoS2 is measured to be 2.15 ± 0.06 eV at 77 K, albeit a higher second conduction band threshold at 0.2 eV above the apparent conduction band minimum is also observed. Combining it with photoluminescence studies, we deduce an exciton binding energy of 0.22 ± 0.1 eV (or 0.42 eV if the second threshold is use), a value that is lower than current theoretical predictions. Consistent with theoretical predictions, we directly observe metallic edge states of single layer MoS 2. In the bulk region of MoS2, the Fermi level is located at 1.8 eV above the valence band maximum, possibly due to the formation of a graphite/MoS2 heterojunction. At the edge, however, we observe an upward band bending of 0.6 eV within a short depletion length of about 5 nm, analogous to the phenomena of Fermi level pinning of a 3D semiconductor by metallic surface states.

Original languageEnglish (US)
Pages (from-to)2443-2447
Number of pages5
JournalNano Letters
Volume14
Issue number5
DOIs
StatePublished - May 14 2014

Keywords

  • Single layer molybdenum sulfide
  • band bending
  • exciton binding energy
  • metallic edge state
  • scanning tunneling microscopy/spectroscopy

ASJC Scopus subject areas

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

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