Phase Identification and Strong Second Harmonic Generation in Pure ε-InSe and Its Alloys
Phase Identification and Strong Second Harmonic Generation in Pure ε-InSe and Its Alloys
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纯ε-InSe及其合金的相识别和强二次谐波产生
DOI：
10.1021/acs.nanolett.9b00487
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发表时间：
2019-04-01
期刊：
影响因子：
10.8
通讯作者：
Zhang, Wenjing
中科院分区：
文献类型：
--
作者：
Hao, Qiaoyan;Yi, Huan;Zhang, Wenjing
二维材料硒化铟(InSe)以其独特的性质为基础研究提供了一个新的平台。与2H相过渡金属二卤化物(TMDs)不同，具有六方晶胞的epsilon相InSe在所有层数上都具有破缺的反转对称性，并预测具有较强的二次谐波产生(SHG)效应。在本工作中，我们发现所制备的纯InSe、合金化InSe_(1-x)Tex和InSe_(1-x)Sx(x=0.1和0.2)为epsilon相结构，并且表现出从少量层到块状尺寸的良好倍频性能。这种高倍频效率归因于epsilon-InSe系统的非中心对称晶体结构，这一点已被像差校正的扫描电子显微镜(STEM)图像清楚地证实。实验结果表明，多层纯InSe和合金化InSe0.9Te0.1和InSe1-xSx(x=0.1和0.2)的倍频强度比单层TMD系统高1-2个数量级，甚至优于相同厚度的GaS系统。估算的非线性极化率X_i((2))大于Ep-Gase和单层TMDs的极化率。我们的研究提供了有关epsilon-inse物相识别的第一手信息，表明它是非线性光学(NLO)应用的极佳候选者，以及通过合金化来工程倍频响应的可能性。
Two-dimensional material indium selenide (InSe) has offered a new platform for fundamental research in virtue of its emerging fascinating properties. Unlike 2H-phase transition-metal dichalcogenides (TMDs), epsilon phase InSe with a hexagonal unit cell possesses broken inversion symmetry in all the layer numbers, and predicted to have a strong second harmonic generation (SHG) effect. In this work, we find that the as-prepared pure InSe, alloyed InSe1-xTex and InSe1-xSx (x = 0.1 and 0.2) are epsilon phase structures and exhibit excellent SHG performance from few-layer to bulk-like dimension. This high SHG efficiency is attributed to the non-centrosymmetric crystal structure of the epsilon-InSe system, which has been clearly verified by aberration-corrected scanning transmission electron microscopy (STEM) images. The experimental results show that the SHG intensities from multilayer pure epsilon-InSe and alloyed InSe0.9Te0.1 and InSe1-xSx (x = 0.1 and 0.2) are around 1-2 orders of magnitude higher than of the monolayer TMD systems and even superior to that of GaSe with the same thickness. The estimated nonlinear susceptibility chi((2)) of epsilon-InSe is larger than that of epsilon-GaSe and monolayer TMDs. Our study provides first-hand information about the phase identification of epsilon-InSe and indicates an excellent candidate for nonlinear optical (NLO) applications as well as the possibility of engineering SHG response by alloying.