Department of Electronics and Nanoengineering, Aalto University, Tietotie 3, Espoo FI-02150, Finland.
Institute of Photonics, University of Eastern Finland, P.O. Box 111, Joensuu FI-80101, Finland.
Nat Commun. 2017 Jun 5;8:15714. doi: 10.1038/ncomms15714.
Grain boundaries have a major effect on the physical properties of two-dimensional layered materials. Therefore, it is important to develop simple, fast and sensitive characterization methods to visualize grain boundaries. Conventional Raman and photoluminescence methods have been used for detecting grain boundaries; however, these techniques are better suited for detection of grain boundaries with a large crystal axis rotation between neighbouring grains. Here we show rapid visualization of grain boundaries in chemical vapour deposited monolayer MoS samples with multiphoton microscopy. In contrast to Raman and photoluminescence imaging, third-harmonic generation microscopy provides excellent sensitivity and high speed for grain boundary visualization regardless of the degree of crystal axis rotation. We find that the contrast associated with grain boundaries in the third-harmonic imaging is considerably enhanced by the solvents commonly used in the transfer process of two-dimensional materials. Our results demonstrate that multiphoton imaging can be used for fast and sensitive characterization of two-dimensional materials.
晶界对二维层状材料的物理性质有重大影响。因此，开发简单、快速和灵敏的用于可视化晶界的表征方法很重要。传统的拉曼和光致发光方法已被用于检测晶界；然而，这些技术更适合检测相邻晶粒之间晶体轴旋转较大的晶界。在这里，我们通过多光子显微镜显示了化学气相沉积单层 MoS 样品中晶界的快速可视化。与拉曼和光致发光成像相比，三阶谐波产生显微镜提供了出色的灵敏度和高速，无论晶体轴旋转程度如何，都可以进行晶界可视化。我们发现，在三阶谐波成像中与晶界相关的对比度通过二维材料的转移过程中常用的溶剂得到了极大的增强。我们的结果表明，多光子成像可用于二维材料的快速和灵敏表征。
