Universal Mechanism of Band-Gap Engineering in Transition-Metal Dichalcogenides

Mingu Kang, Beomyoung Kim, Sae Hee Ryu, Sung Won Jung, Jimin Kim, Luca Moreschini, Chris Jozwiak, Eli Rotenberg, Aaron Bostwick, Keun Su Kim

Research output: Contribution to journalArticlepeer-review

132 Citations (Scopus)


van der Waals two-dimensional (2D) semiconductors have emerged as a class of materials with promising device characteristics owing to the intrinsic band gap. For realistic applications, the ideal is to modify the band gap in a controlled manner by a mechanism that can be generally applied to this class of materials. Here, we report the observation of a universally tunable band gap in the family of bulk 2H transition metal dichalcogenides (TMDs) by in situ surface doping of Rb atoms. A series of angle-resolved photoemission spectra unexceptionally shows that the band gap of TMDs at the zone corners is modulated in the range of 0.8-2.0 eV, which covers a wide spectral range from visible to near-infrared, with a tendency from indirect to direct band gap. A key clue to understanding the mechanism of this band-gap engineering is provided by the spectroscopic signature of symmetry breaking and resultant spin-splitting, which can be explained by the formation of 2D electric dipole layers within the surface bilayer of TMDs. Our results establish the surface Stark effect as a universal mechanism of band-gap engineering on the basis of the strong 2D nature of van der Waals semiconductors.

Original languageEnglish
Pages (from-to)1610-1615
Number of pages6
JournalNano letters
Issue number3
Publication statusPublished - 2017 Mar 8

Bibliographical note

Publisher Copyright:
© 2017 American Chemical Society.

All Science Journal Classification (ASJC) codes

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


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