title: Engineering Optical and Electronic Properties of WS2 by Varying the Number of Layers.
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.
authors.affiliation: †Division of Quantum Phases and Devices, Department of Physics, Konkuk University, Seoul 143-701, Korea.
authors.forename: Hyun-Cheol
authors.initials: HC
authors.lastname: Kim
authors.affiliation: †Division of Quantum Phases and Devices, Department of Physics, Konkuk University, Seoul 143-701, Korea.
authors.forename: Hakseong
authors.initials: H
authors.lastname: Kim
authors.affiliation: §Department of Physics, Sogang University, Seoul 121-742, Korea.
authors.forename: Jae-Ung
authors.initials: JU
authors.lastname: Lee
authors.affiliation: †Division of Quantum Phases and Devices, Department of Physics, Konkuk University, Seoul 143-701, Korea.
authors.forename: Han-Byeol
authors.initials: HB
authors.lastname: Lee
authors.affiliation: †Division of Quantum Phases and Devices, Department of Physics, Konkuk University, Seoul 143-701, Korea.
authors.forename: Doo-Hua
authors.initials: DH
authors.lastname: Choi
authors.affiliation: †Division of Quantum Phases and Devices, Department of Physics, Konkuk University, Seoul 143-701, Korea.
authors.forename: Jun-Ho
authors.initials: JH
authors.lastname: Lee
authors.affiliation: ‡Department of Organic and Nano System Engineering, Konkuk University, Seoul, 143-701, Korea.
authors.forename: Wi Hyoung
authors.initials: WH
authors.lastname: Lee
authors.affiliation: †Division of Quantum Phases and Devices, Department of Physics, Konkuk University, Seoul 143-701, Korea.
authors.forename: Sung Ho
authors.initials: SH
authors.lastname: Jhang
authors.affiliation: †Division of Quantum Phases and Devices, Department of Physics, Konkuk University, Seoul 143-701, Korea.
authors.forename: Bae Ho
authors.initials: BH
authors.lastname: Park
authors.affiliation: §Department of Physics, Sogang University, Seoul 121-742, Korea.
authors.forename: Hyeonsik
authors.initials: H
authors.lastname: Cheong
authors.affiliation: †Division of Quantum Phases and Devices, Department of Physics, Konkuk University, Seoul 143-701, Korea.
authors.forename: Sang-Wook
authors.initials: SW
authors.lastname: Lee
authors.affiliation: †Division of Quantum Phases and Devices, Department of Physics, Konkuk University, Seoul 143-701, Korea.
authors.forename: Hyun-Jong
authors.initials: HJ
authors.lastname: Chung
keywords: Schottky barrier; band-alignment; bandgap; transition-metal dichalcogenide; tungsten disulfide