Microscale Spectroscopic Mapping of 2D Optical Materials

Abstract 2D materials have unique optical properties due to their ultrathin layered structures, and are emerging as promising materials for optoelectronic devices. To characterize and evaluate these properties, diffraction‐limited spectroscopic mapping, also known as microscale spectroscopic imaging, has been developed to provide abundant spatial and spectral information. The usefulness of microscale spectroscopic mapping for unique property study of 2D optical materials is addressed. Advances in both mature and growing microscale spectroscopic mapping setups and methods covering broad ranges of the electromagnetic spectrum are introduced. Different forms of graphene, molybdenum disulphide (MoS 2 ), and black phosphorus, including intrinsic and engineered structures made by different methods, are selected as varied representatives of 2D optical materials from the perspective of bandgap and anisotropy. A detailed discussion of microscale spectroscopic images and their unique optical property findings, including spatial adsorption and emission, excitonic behavior, light sensitivity, and plasmonic effects, is then given to demonstrate the advantages of spectral mapping over conventional point spectroscopy. The analysis also provides a generic view of microscale spectroscopic mapping selection in 2D‐materials imaging. Furthermore, the challenges inherent in large‐scale spectral data processing are explored, and the utilization of deep learning is suggested for possible application in academica and industry.