Layer-Dependent Optical Conductivity in Atomic Thin WS2 by Reflection Contrast Spectroscopy

被引:36
作者
Nayak, Pramoda K. [1 ]
Yeh, Chao-Hui [1 ]
Chen, Yu-Chen [1 ]
Chiu, Po-Wen [1 ]
机构
[1] Natl Tsing Hua Univ, Dept Elect Engn, Hsinchu 30013, Taiwan
关键词
optical conductivity; WS2; transition metal dichalcogenides; reflection contrast spectroscopy; semiconductors; VALLEY POLARIZATION; BAND-STRUCTURES; MONOLAYER MOS2; GRAPHENE; RAMAN; DICHALCOGENIDES;
D O I
10.1021/am5039483
中图分类号
TB3 [工程材料学];
学科分类号
0805 ; 080502 ;
摘要
Optical conductivity, which originates from the interband transition due to electron-phonon interaction, is one of the powerful tools used for studying the electronic states in layered transition metal dichalcogenides (TMDCs). Here, we report for the first time the optical conductivity of WS2,, one of the emerging classes of TMDCs, prepared directly on SiO2/Si substrate using reflection contrast spectroscopy. The measured optical conductivity at direct excitonic transition point K of the Brillouin zone for monolayer WS2 shows a value of 0.37 e(2)/pi h in the visible range of the energy spectrum. Our results reveal that the optical conductivity of WS2 layers is frequency-dependent and show additional features in the conductivity spectra for bilayer to bulk counterparts, signifying a transition from direct band gap to indirect band gap with the evolution of layer numbers as predicted by our calculations.
引用
收藏
页码:16020 / 16026
页数:7
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