Engineering Optical and Electronic Properties of WS2 by Varying the Number of Layers

Hyun Cheol Kim, Hakseong Kim, Jae Ung Lee, Han Byeol Lee, Doo Hua Choi, Jun Ho Lee, Wi Hyoung Lee, Sung Ho Jhang, Bae Ho Park, Hyeonsik Cheong, Sang Wook Lee, Hyun Jong Chung

Research output: Contribution to journalArticlepeer-review

75 Scopus citations

Abstract

The optical constants, bandgaps, and band alignments of mono-, bi-, and trilayer WS2 were experimentally measured, and an extraordinarily high dependency on the number of layers was revealed. The refractive indices and extinction coefficients were extracted from the optical-contrast oscillation for various thicknesses of SiO2 on a Si substrate. The bandgaps of the few-layer WS2 were both optically and electrically measured, indicating high exciton-binding energies. The Schottky-barrier heights (SBHs) with Au/Cr contact were also extracted, depending on the number of layers (1-28). From an engineering viewpoint, the bandgap can be modulated from 3.49 to 2.71 eV with additional layers. The SBH can also be reduced from 0.37 eV for a monolayer to 0.17 eV for 28 layers. The technique of engineering materials properties by modulating the number of layers opens pathways uniquely adaptable to transition-metal dichalcogenides.

Original languageEnglish
Pages (from-to)6854-6860
Number of pages7
JournalACS Nano
Volume9
Issue number7
DOIs
StatePublished - 28 Jul 2015

Keywords

  • Schottky barrier
  • band-alignment
  • bandgap
  • transition-metal dichalcogenide
  • tungsten disulfide

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