Direct imaging of band profile in single layer MoS 2 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

315 Scopus citations

Abstract

Using scanning tunneling microscopy and spectroscopy, we probe the electronic structures of single layer MoS 2 on graphite. The apparent quasiparticle energy gap of single layer MoS 2 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 MoS 2 , the Fermi level is located at 1.8 eV above the valence band maximum, possibly due to the formation of a graphite/MoS 2 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

Fingerprint Dive into the research topics of 'Direct imaging of band profile in single layer MoS <sub>2</sub> on graphite: Quasiparticle energy gap, metallic edge states, and edge band bending'. Together they form a unique fingerprint.

Cite this