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

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• 作者：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
• 刊名：ACS Nano
• 出版年：2015
• 出版时间：July 28, 2015
• 年：2015
• 卷：9
• 期：7
• 页码：6854-6860
• 全文大小：501K
• ISSN：1936-086X

文摘

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鈥?8). 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鈥?properties by modulating the number of layers opens pathways uniquely adaptable to transition-metal dichalcogenides.