Optical spectroscopy study of two-dimensional materials

Two-dimensional materials (2DMs), with covalent bonds for the atoms within a rigid layer but van der Waals interactions for interlayer coupling, are widely applied across many research fields including optoelectronics, nanoelectronics, and photovoltaics based on their unique optical properties, which can be modulated by their interlayer coupling, number of layers, stacking order, and even the assemblies in related van der Waals heterostructures (vdWHs). Through light-matter interaction, optical spectroscopy is widely utilized to investigate physical properties, such as electronic band structure, lattice vibrations, electron-phonon coupling, etc. In this chapter, we focus on the recent advancements of optical spectroscopy study of 2DMs, beginning with an overview of various 2DMs and the related vdWHs. Various two-dimensional (2D) systems give rise to abundant novel physical properties, which can be probed by optical contrast, photoluminescence spectroscopy, Rayleigh scattering, Raman spectroscopy, second-harmonic generation, and so on. The above commonly used optical spectroscopy techniques are demonstrated in detail with a series of typical examples of 2DMs. The approaches addressed in this chapter can be extended to the large family of 2D systems, which pave ways to enrich the understanding of their optical and electronic properties.