Graphene Research Centre, National University of Singapore, 117546 Singapore.
Sci Rep. 2013;3:2593. doi: 10.1038/srep02593.
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).
在本文中，我们报道了首例通过机械剥离技术成功制备单层和少层二硒化钽（2H-TaSe₂）的成果。层数通过白光对比光谱法和原子力显微镜（AFM）确认。原子层厚度的振动特性通过微拉曼光谱进行了表征。室温拉曼测量表明，具有可靠的厚度确定能力，其光谱特征类似于 MoS₂。在支撑的 TaSe₂ 层中观察到 E₁g 模式，该模式在背散射拉曼配置中通常是禁止的，而在悬空层中消失，表明该模式可能由于与衬底相互作用引起的对称性破缺而被激活。首次进行的系统原位低温拉曼研究揭示了在单层和双层 2H-TaSe₂ 中存在非调谐电荷密度波相变，这反映在由强电子-声子耦合（科恩反常）引起的二阶宽拉曼模式的突然软化。
