Resonant Raman and Exciton Coupling in High-Quality Single Crystals of Atomically Thin Molybdenum Diselenide Grown by Vapor-Phase Chalcogenization.
Resonant Raman and Exciton Coupling in High-Quality Single Crystals of Atomically Thin Molybdenum Diselenide Grown by Vapor-Phase Chalcogenization.
复制标题
气相硫属化生长的原子薄二硒化钼高质量单晶中的共振拉曼和激子耦合。
DOI：
10.1021/acsnano.7b07933
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发表时间：
2018
期刊：
影响因子：
17.1
通讯作者：
S. Kar
中科院分区：
文献类型：
--
作者：
Ismail Bilgin;A. Raeliarijaona;Michael C. Lucking;Sebastian Cooper Hodge;A. Mohite;A. de Luna Bugallo;H. Terrones;S. Kar
我们报告了一个详细的调查拉曼光谱气相硫族化生长，高品质的单晶原子薄的二硒化钼样品。在具有范围从1.95 eV至Eex至2.71 eV的四种不同入射激光激发能量的样品中进行测量，揭示了范围从N = 1-4层的样品和厚的块状样品中的丰富光谱信息。除了先前观察到的（和确定的）峰，我们特别研究了ω = 250 cm-1附近的峰的起源。我们的密度泛函理论和Bethe-Salpeter计算表明，这个峰来自一个双共振拉曼过程涉及ZA声学声子垂直于层。该模式在新鲜制备的样品中显著出现，在老化样品中消失，从而提供了一种用于确定新鲜制备的2D-MoSe 2晶体的高光电质量的方法。我们进一步提出了这个和其他峰的位置的能量依赖性变化的深入调查，并提供证据的C-激子-声子耦合在单层MoSe 2。最后，我们展示了如何在这些样品中的层厚度的函数的签名峰的位置和强度变化。
We report a detailed investigation on Raman spectroscopy in vapor-phase chalcogenization grown, high-quality single-crystal atomically thin molybdenum diselenide samples. Measurements were performed in samples with four different incident laser excitation energies ranging from 1.95 eV ⩽ Eex ⩽ 2.71 eV, revealing rich spectral information in samples ranging from N = 1-4 layers and a thick, bulk sample. In addition to previously observed (and identified) peaks, we specifically investigate the origin of a peak near ω ≈ 250 cm-1. Our density functional theory and Bethe-Salpeter calculations suggest that this peak arises from a double-resonant Raman process involving the ZA acoustic phonon perpendicular to the layer. This mode appears prominently in freshly prepared samples and disappears in aged samples, thereby offering a method for ascertaining the high optoelectronic quality of freshly prepared 2D-MoSe2 crystals. We further present an in-depth investigation of the energy-dependent variation of the position of this and other peaks and provide evidence of C-exciton-phonon coupling in monolayer MoSe2. Finally, we show how the signature peak positions and intensities vary as a function of layer thickness in these samples.