Electronic structure of a quasi-freestanding MoS2 monolayer

T. Eknapakul, P. D. C. King*, M. Asakawa, P. Buaphet, R. -H. He, S. -K. Mo, H. Takagi, K. M. Shen, F. Baumberger, T. Sasagawa, S. Jungthawan, W. Meevasana

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

144 Citations (Scopus)


Several transition-metal dichalcogenides exhibit a striking crossover from indirect to direct band gap semiconductors as they are thinned down to a single monolayer. Here, we demonstrate how an electronic structure characteristic of the isolated monolayer can be created at the surface of a bulk MoS2 crystal. This is achieved by intercalating potassium in the interlayer van der Waals gap, expanding its size while simultaneously doping electrons into the conduction band. Our angle-resolved photoemission measurements reveal resulting electron pockets centered at the (K) over bar and (K') over bar points of the Brillouin zone, providing the first momentum-resolved measurements of how the conduction band dispersions evolve to yield an approximately direct band gap of 1.8 eV in quasi-freestanding monolayer MoS2. As well as validating previous theoretical proposals, this establishes a novel methodology for manipulating electronic structure in transition-metal dichalcogenides, opening a new route for the generation of large-area quasi-freestanding monolayers for future fundamental study and use in practical applications.

Original languageEnglish
Pages (from-to)1312-1316
Number of pages5
JournalNano Letters
Issue number3
Early online date19 Feb 2014
Publication statusPublished - 12 Mar 2014


  • Molybdenum disulfide (MoS2)
  • Transition metal dichalcogenides (TMD)
  • Layered semiconductor
  • Electronic structure
  • Angle-resolved photoemission
  • van der Waals expansion


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