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Twist Angle-Dependent Optical Responses in Controllably Grown WS2 Vertical Homojunctions
Chemistry of Materials ( IF 8.6 ) Pub Date : 2020-11-10 , DOI: 10.1021/acs.chemmater.0c03413
Gonglei Shao 1 , Xiong-Xiong Xue 2, 3 , Xiao Liu 1 , Danliang Zhang 4 , Yuanyuan Jin 1 , Yangwu Wu 1 , Bingying You 1 , Yung-Chang Lin 5 , Shisheng Li 6 , Kazu Suenaga 5 , Xiao Wang 4 , Anlian Pan 7 , Huimin Li 1 , Jinhua Hong 5 , Yexin Feng 2 , Song Liu 1
Affiliation  

Interlayer coupling in two-dimensional (2D) materials with specific stacking modes results in angle-dependent electrical and optical behaviors. Compared to multilayered WS2 with a 0° twist angle grown under normal conditions, WS2 sheets with a 60° twist angle are prepared by chemical vapor deposition (CVD) with the assistance of tin (Sn) for reducing stacking energy. The layer number can be effectively regulated by the growth temperature and hydrogen flow. The 2H-like phase of the 60° bilayer structure is revealed by scanning transmission electron microscopy (STEM), displaying intense photoluminescence (PL) variation and diverse second harmonic generation due to interlayer coupling. The bilayer WS2 with various twist angles can be obtained for angle-dependent Raman/PL response. Density functional theory (DFT) calculations demonstrate that heteroatom Sn can tip the balance between 0° and 60° bilayers, facilitating the formation of the bilayer with a 60° stacking angle. The heteroatom-assisted approach provides a general strategy for the self-assembly of 2D materials. The heterostructures with tunable twist angles can be prepared, which broadens their applications in moiré excitons, spintronics, and valley electronics of transition metal dichalcogenides.

中文翻译:

可控生长的WS 2垂直同质结中与扭曲角有关的光学响应

具有特定堆叠模式的二维(2D)材料中的层间耦合会导致角度相关的电气和光学行为。与在正常条件下具有0°扭曲角的多层WS 2相比,在锡(Sn)的辅助下通过化学气相沉积(CVD)制备了具有60°扭曲角的WS 2薄板,以减少堆叠能量。层数可以通过生长温度和氢气流量有效地调节。通过扫描透射电子显微镜(STEM)揭示了60°双层结构的2H样相,由于层间耦合,显示出强烈的光致发光(PL)变化和多样的二次谐波生成。双层WS 2对于依赖于角度的拉曼/ PL响应,可以获得具有各种扭转角的角度。密度泛函理论(DFT)计算表明,杂原子Sn可以使0°和60°双层之间的平衡倾斜,从而有利于以60°堆叠角形成双层。杂原子辅助方法为2D材料的自组装提供了一般策略。可以制备具有可调扭转角的异质结构,从而拓宽了它们在莫尔激子,自旋电子学和过渡金属二卤化硅谷电子中的应用。
更新日期:2020-11-25
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