Department of Physics, Yonsei University , Seoul 120-749, Korea.
Division of Physics and Semiconductor Science, Dongguk University , Seoul 100-715, Korea.
ACS Appl Mater Interfaces. 2017 Sep 13;9(36):30786-30796. doi: 10.1021/acsami.7b05475. Epub 2017 Aug 31.
Transition metal dichalcogenides (TMDCs) are promising next-generation materials for optoelectronic devices because, at subnanometer thicknesses, they have a transparency, flexibility, and band gap in the near-infrared to visible light range. In this study, we examined continuous, large-area MoSe film, grown by molecular beam epitaxy on an amorphous SiO/Si substrate, which facilitated direct device fabrication without exfoliation. Spectroscopic measurements were implemented to verify the formation of a homogeneous MoSe film by performing mapping on the micrometer scale and measurements at multiple positions. The crystalline structure of the film showed hexagonal (2H) rotationally stacked layers. The local strain at the grain boundaries was mapped using a geometric phase analysis, which showed a higher strain for a 30° twist angle compared to a 13° angle. Furthermore, the photon-matter interaction for the rotational stacking structures was investigated as a function of the number of layers using spectroscopic ellipsometry. The optical band gap for the grown MoSe was in the near-infrared range, 1.24-1.39 eV. As the film thickness increased, the band gap energy decreased. The atomically controlled thin MoSe showed promise for application to nanoelectronics, photodetectors, light emitting diodes, and valleytronics.
过渡金属二卤族化合物（TMDCs）是下一代光电器件有前途的材料，因为在亚纳米厚度下，它们在近红外到可见光范围内具有透明度、柔韧性和带隙。在这项研究中，我们研究了连续的大面积 MoSe 薄膜，它通过分子束外延在非晶态 SiO/Si 衬底上生长，这便于直接进行器件制造而无需剥离。通过在微米尺度上进行映射和在多个位置进行测量，进行了光谱测量以验证均匀 MoSe 薄膜的形成。该薄膜的晶体结构表现出六方（2H）旋转堆叠层。使用几何相位分析映射了晶界处的局部应变，结果表明 30°扭曲角的应变高于 13°角的应变。此外，使用光谱椭圆偏振法研究了旋转堆叠结构的光子物质相互作用作为层数的函数。生长的 MoSe 的光学带隙在近红外范围内，为 1.24-1.39eV。随着薄膜厚度的增加，带隙能量降低。原子控制的薄 MoSe 有望应用于纳米电子学、光电探测器、发光二极管和谷电子学。
