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Raman studies in 2D materials

Speaker: 
C. Qiu, C. Cong, and P. Hajiyev (Yu Ting's group, NTU)
Date: 
Wed, 10/04/2013 - 11:00am to 12:00pm
Location: 
S13-M01-11 (Physics Conference Room)
Event Type: 
Seminars

Abstract

Using our custom-designed measuring setup, we performed magneto-Raman spectroscopy and imaging on high quality graphene decoupled from graphite, and on ABA-/ABC- stacked trilayer graphene (TLG) samples. For decoupled graphene, a high resolution magneto phonon resonance (MPR) Raman data are obtained, which are proven by the new observation of triplet splitting of the G mode and the appearance of eight traces showing the crossing of the G mode with the anti-crossing MPR behaviour. For trilayer graphene samples, it is found that the Raman features of the E2g phonon oscillate with the magnetic fields in both supported and suspended ABA-stacked TLG, which indicates the existence of MPR and its weak dependence on the substrate. In contrast, the E2g phonon of ABC-stacked TLG are inert to the magnetic field up to 9 T. All of these magnetic field-dependent spectral features are explained by the proposed theoretical models.

We also conducted Raman studies on 2D Tantalum Dislenide (TaSe2) samples, which has a unique charge density wave (CDW) phase at 123 K and 90 K followed by possible superconductivity at even lower temperatures. Single- and few-layers of 2H-TaSe2 were successfully exfoliated and room temperature Raman measurements demonstrate MoS2-like spectral features, which are reliable for thickness determination. Furthermore, in-situ low temperature Raman study has been conducted and the CDW phase related properties of single- and bi-layered TaSe2 samples have been observed for the first time.

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