Atomically thin, two-dimensional (2D) indium selenide (InSe) has attracted considerable attention because of the dependence of its bandgap on sample thickness, making it suitable for small-scale optoelectronic device applications. In this work, by the use of Raman spectroscopy with three different laser wavelengths, including 488, 532, and 633 nm, representing resonant, near-resonant, and conventional nonresonant conditions, a conclusive understanding of the thickness dependence of lattice vibrations and electronic band structure of InSe and InSe/graphene heterostructures is presented. Combining our experimental measurements with first-principles quantum mechanical modeling of the InSe systems, we identified the crystal structure as ε-phase InSe and demonstrated that its measured intensity ratio of Raman peaks in the resonant Raman spectrum evolves with the number of layers. Moreover, graphene coating enhances Raman scattering of few-layered InSe and also makes its photoluminescence stable under higher intensity laser illumination. The optically induced charge transfer between van der Waals graphene/InSe heterostructures is observed under excitation of the E′ transition in InSe, where the observed mechanism may potentially be a route for future integrated electronic and optoelectronic devices.

中文翻译：

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硒化铟和硒化铟/石墨烯异质结构的厚度依赖性共振拉曼光谱和E'光致发光光谱

原子薄的二维（2D）硒化铟（InSe）由于其带隙对样品厚度的依赖性而备受关注，从而使其适合于小型光电器件应用。在这项工作中，通过使用拉曼光谱法，使用三种不同的激光波长（包括488、532和633 nm），分别代表共振，近共振和常规非共振条件，对晶格振动和电子带的厚度依赖性有了结论性的理解。介绍了InSe的结构和InSe /石墨烯的异质结构。将我们的实验测量结果与InSe系统的第一性原理量子力学建模相结合，我们将晶体结构鉴定为ε相InSe，并证明了其在共振拉曼光谱中测得的拉曼峰强度比随层数的变化而变化。此外，石墨烯涂层增强了几层InSe的拉曼散射，并使其在高强度激光照射下的光致发光稳定。在InSe中E'跃迁的激发下，观察到范德华石墨烯/ InSe异质结构之间的光诱导电荷转移，其中观察到的机制可能是未来集成电子和光电器件的途径。