二次谐波在二维材料结构表征中的应用

二次谐波作为非线性光学的重要分支,逐渐成为表征晶体结构的重要手段之一。在众多表征方法中,二次谐波因其无损检测、高稳定性、可调谐性、超快响应、偏振敏感性、通用性、操作简单等特点被广泛应用于二维材料结构表征,为二维材料的物性研究和功能应用提供了重要信息,大大推动了二维材料基础研究的快速发展。本文综述了近几年二次谐波在二维材料结构表征中的研究,简述了二次谐波产生原理,介绍了飞秒激光器接入共聚焦拉曼光谱仪产生二次谐波测试装置,分别讨论了二次谐波在二维材料的层间堆垛层数、层间堆垛角度、单层二维材料晶界及晶体取向表征方面的应用。同时,本文还介绍了采用二次谐波强度直接、灵敏地检测晶体中应变幅度以及通过二次谐波信号变化跟踪材料中的缺陷变化,接着讨论了二次谐波与拉曼光谱、光致发光的多维度关联分析在材料全面深度表征方面的重要性。最后展望了二次谐波未来在材料结构表征中的潜在研究方向。

Application of Second Harmonic Generation in Characterization of 2D Materials

As an important branch of nonlinear optics, second harmonic generation (SHG) is becoming one of the most important means to characterize crystal structure. Among various methods of characterization, because of nondestructive detection, high stability, tunability, ultrafast response, polarization sensitivity, versatility and simplicity, SHG is widely used to characterize the structure of two-dimensional (2D) materials. It provides important information for the physical properties and functional applications of 2D materials, as well as greatly promotes the rapid development of basic research on 2D materials. Here, the current state of the art focuses on the recent research work of SHG in 2D material structure characterization. Firstly, the principle of the second harmonic generation is briefly introduced. Then, the second harmonic generation device with femtosecond laser connected to confocal Raman spectrometer is taken as an example to present the mechanism of SHG. Afterwards, the applications of SHG are demonstrated in the thickness of interlayer stacking of 2D materials, the stacking angle between different layers of 2D materials, the grain boundary and the crystal orientation of monolayer 2D materials. The second harmonic intensity is used as a direct and sensitive means to monitor the strain amplitude, and the SHG signal changes are used to track defects in materials. Meanwhile, the importance of multi-dimensional correlation analysis of second harmonic generation, Raman spectroscopy and photoluminescence in comprehensive and in-depth characterization of materials is also explored. Finally, the potential research directions and prospects based on SHG in material characterization in the future is prospected.