Hajiyev P, Cong C, Qiu C, Yu T. Contrast and Raman spectroscopy study of single- and few-layered charge density wave material: 2H-TaSe₂.
Sci Rep 2013;
3:2593. [PMID:
24005335 PMCID:
PMC3763362 DOI:
10.1038/srep02593]
[Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2013] [Accepted: 08/19/2013] [Indexed: 12/24/2022] Open
Abstract
In this article, we report the first successful preparation of single- and few-layers of tantalum diselenide (2H-TaSe₂) by mechanical exfoliation technique. Number of layers is confirmed by white light contrast spectroscopy and atomic force microscopy (AFM). Vibrational properties of the atomically thin layers of 2H-TaSe₂ are characterized by micro-Raman spectroscopy. Room temperature Raman measurements demonstrate MoS₂-like spectral features, which are reliable for thickness determination. E₁g mode, usually forbidden in backscattering Raman configuration is observed in the supported TaSe₂ layers while disappears in the suspended layers, suggesting that this mode may be enabled because of the symmetry breaking induced by the interaction with the substrate. A systematic in-situ low temperature Raman study, for the first time, reveals the existence of incommensurate charge density wave phase transition in single and double-layered 2H-TaSe₂ as reflected by a sudden softening of the second-order broad Raman mode resulted from the strong electron-phonon coupling (Kohn anomaly).
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