Abstract We report on the temperature-dependence Raman modes of in-plane B 3 g , A g 2 and out-of-plane A g 1 , A g 3 in single crystals of tin selenide that grown by a modified home-made Bridgeman method. The samples are characterized by single crystal X-ray diffraction and high-resolution transmission electron microscopy to confirm their crystal structure. The temperature-dependence of Raman spectroscopy illustrates that A g 1 , B 3 g , A g 2 and A g 3 modes are red-shifted and softened with increasing temperature from 77 K to 400 K. Large temperature coefficients for in-plane Raman modes are observed, say −4.13 × 10−2 cm−1/K and −5.20 × 10−2 cm−1/K for B 3 g and A g 2 modes, respectively. The values for out-of-plane modes are much lower, say −0.91 × 10−2 cm−1/K and −1.38 × 10−2 cm−1/K for A g 1 and A g 3 modes, respectively. The result indicates intrinsic anisotropic Gruneisen parameter β in SnSe, revealing the strong anisotropic lattice anharmonicity. Besides, coefficients of optical-phonon frequency with incident laser-power were (−0.87, −2.77, −2.18 and −1.08) cm−1/mW for A g 1 , B 3 g , A g 2 and A g 3 , respectively for the laser-power dependent Raman spectroscopy experiments. Our work offers a new insight to understand the lattice anharmonicity via Raman spectroscopy and is conductive to search the new thermoelectric materials with intrinsic low lattice thermal conductivity.

中文翻译：

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单晶 SnSe 中拉曼散射的温度依赖性

摘要 我们报告了通过改进的自制布里奇曼方法生长的硒化锡单晶中面内 B 3 g , A g 2 和面外 A g 1 , A g 3 的温度依赖性拉曼模式. 样品通过单晶 X 射线衍射和高分辨率透射电子显微镜进行表征，以确认其晶体结构。拉曼光谱的温度依赖性说明 A g 1 、B 3 g 、A g 2 和 A g 3 模式随着温度从 77 K 升高到 400 K 发生红移和软化。 面内拉曼模式的温度系数大分别观察到 B 3 g 和 A g 2 模式的 -4.13 × 10-2 cm-1/K 和 -5.20 × 10-2 cm-1/K。面外模式的值要低得多，例如对于 Ag 1 和 Ag 3 模式分别为 -0.91 × 10-2 cm-1/K 和 -1.38 × 10-2 cm-1/K。结果表明 SnSe 中固有的各向异性 Gruneisen 参数 β，揭示了强烈的各向异性晶格非谐性。此外，A g 1 、B 3 g 、A g 2 和A g 3 的光声子频率与入射激光功率的系数分别为（-0.87、-2.77、-2.18和-1.08）cm-1/mW用于激光功率相关的拉曼光谱实验。我们的工作为通过拉曼光谱理解晶格非谐性提供了新的见解，并有助于寻找具有固有低晶格热导率的新型热电材料。分别用于激光功率相关的拉曼光谱实验。我们的工作为通过拉曼光谱理解晶格非谐性提供了新的见解，并有助于寻找具有固有低晶格热导率的新型热电材料。分别用于激光功率相关的拉曼光谱实验。我们的工作为通过拉曼光谱理解晶格非谐性提供了新的见解，并有助于寻找具有固有低晶格热导率的新型热电材料。