Raman Signatures of Polytypism in Molybdenum Disulfide

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• 作者：Jae-Ung Lee ; Kangwon Kim ; Songhee Han ; Gyeong Hee Ryu ; Zonghoon Lee ; Hyeonsik Cheong
• 刊名：ACS Nano
• 出版年：2016
• 出版时间：February 23, 2016
• 年：2016
• 卷：10
• 期：2
• 页码：1948-1953
• 全文大小：684K
• ISSN：1936-086X

文摘

Since the stacking order sensitively affects various physical properties of layered materials, accurate determination of the stacking order is important for studying the basic properties of these materials as well as for device applications. Because 2H-molybdenum disulfide (MoS₂) is most common in nature, most studies so far have focused on 2H-MoS₂. However, we found that the 2H, 3R, and mixed stacking sequences exist in few-layer MoS₂ exfoliated from natural molybdenite crystals. The crystal structures are confirmed by HR-TEM measurements. The Raman signatures of different polytypes are investigated by using three different excitation energies that are nonresonant and resonant with A and C excitons, respectively. The low-frequency breathing and shear modes show distinct differences for each polytype, whereas the high-frequency intralayer modes show little difference. For resonant excitations at 1.96 and 2.81 eV, distinct features are observed that enable determination of the stacking order.