Direct observation of the transition from indirect to direct bandgap in atomically thin epitaxial MoSe2

Yi Zhang, Tay Rong Chang, Bo Zhou, Yong Tao Cui, Hao Yan, Zhongkai Liu, Felix Schmitt, James Lee, Rob Moore, Yulin Chen, Hsin Lin, Horng Tay Jeng, Sung Kwan Mo, Zahid Hussain, Arun Bansil, Zhi Xun Shen

Research output: Contribution to journalArticlepeer-review

765 Citations (Scopus)

Abstract

Quantum systems in confined geometries are host to novel physical phenomena. Examples include quantum Hall systems in semiconductors and Dirac electrons in graphene. Interest in such systems has also been intensified by the recent discovery of a large enhancement in photoluminescence quantum efficiency and a potential route to valleytronics in atomically thin layers of transition metal dichalcogenides, MX2 (M = Mo, W; X = S, Se, Te), which are closely related to the indirect-to-direct bandgap transition in monolayers. Here, we report the first direct observation of the transition from indirect to direct bandgap in monolayer samples by using angle-resolved photoemission spectroscopy on high-quality thin films of MoSe2 with variable thickness, grown by molecular beam epitaxy. The band structure measured experimentally indicates a stronger tendency of monolayer MoSe2 towards a direct bandgap, as well as a larger gap size, than theoretically predicted. Moreover, our finding of a significant spin-splitting of ∼180 meV at the valence band maximum of a monolayer MoSe2 film could expand its possible application to spintronic devices.

Original languageEnglish
Pages (from-to)111-115
Number of pages5
JournalNature Nanotechnology
Volume9
Issue number2
DOIs
Publication statusPublished - 2014 Feb

All Science Journal Classification (ASJC) codes

  • Bioengineering
  • Atomic and Molecular Physics, and Optics
  • Biomedical Engineering
  • Materials Science(all)
  • Condensed Matter Physics
  • Electrical and Electronic Engineering

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