Abstract The exciton-phonon coupling plays an important role in the optical properties of two-dimensional (2D) materials. In the preparation of 2D TMDC films, there are often different degrees of intrinsic defects, which have significant impacts on their optical and electrical properties. Here, we have investigated the effect of intrinsic defects on resonant Raman spectroscopy (RRS) in WS2. In a modified chemical vapor deposition (CVD) process, flower-like (with three petaloids) WS2 bilayers (FLO-B) and trilayers (FLO-T) can be produced in S-rich condition. It was found that the LA(M), E12g, A1g Raman modes and excitons of flower-like WS2 exhibit abnormal behaviors due to the rich defects in the flower-like WS2 flakes. The population of XD gets increased and the shift of its binding energy is ~30 meV larger than that of A0 for the defective flower-like WS2, which leads to greatly enhanced exciton-phonon interaction. Under low-frequency RRS, the appearance of petal morphology greatly enhances the scattering intensity and activate the SM32 phonon mode, normally not seen for backscattering. The appearance of this defect-assisted phonon mode is also related to the increase of scattering cross-section and exciton Bohr radius. Our work reveals the feasibility of shape-controlled exciton-phonon interactions in defective WS2 films and improves our understanding of the light-matter interaction principles in this material.

中文翻译：

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花状WS2薄膜与邻近层之间缺陷介导的强激子-声子耦合

摘要 激子-声子耦合在二维 (2D) 材料的光学性质中起着重要作用。在二维TMDC薄膜的制备过程中，往往存在不同程度的固有缺陷，这对其光学和电学性能产生了显着影响。在这里，我们研究了固有缺陷对 WS2 共振拉曼光谱 (RRS) 的影响。在改良的化学气相沉积 (CVD) 工艺中，可以在富含 S 的条件下生产花状（具有三个花瓣）WS2 双层 (FLO-B) 和三层 (FLO-T)。发现由于花状WS2薄片中的丰富缺陷，花状WS2的LA(M)、E12g、A1g拉曼模式和激子表现出异常行为。对于有缺陷的花状 WS2，XD 的数量增加，其结合能的变化比 A0 大~30 meV，这导致激子 - 声子相互作用大大增强。在低频 RRS 下，花瓣形态的出现大大增强了散射强度并激活了 SM32 声子模式，通常在背向散射中看不到。这种缺陷辅助声子模式的出现也与散射截面和激子玻尔半径的增加有关。我们的工作揭示了在有缺陷的 WS2 薄膜中形状控制的激子 - 声子相互作用的可行性，并提高了我们对这种材料中光-物质相互作用原理的理解。花瓣形态的出现大大增强了散射强度并激活了 SM32 声子模式，通常在背向散射中看不到。这种缺陷辅助声子模式的出现也与散射截面和激子玻尔半径的增加有关。我们的工作揭示了在有缺陷的 WS2 薄膜中形状控制的激子 - 声子相互作用的可行性，并提高了我们对这种材料中光-物质相互作用原理的理解。花瓣形态的出现大大增强了散射强度并激活了 SM32 声子模式，通常在背向散射中看不到。这种缺陷辅助声子模式的出现也与散射截面和激子玻尔半径的增加有关。我们的工作揭示了在有缺陷的 WS2 薄膜中形状控制的激子 - 声子相互作用的可行性，并提高了我们对这种材料中光-物质相互作用原理的理解。