In-situ optical observation of atomically-thin two-dimensional material growth in chemical vapor deposition for improved precise control

The growth of two-dimensional atomic layer materials (2D materials), including graphene and transition metal dichalcogenides (TMDCs), has been significantly advanced by in-situ observation techniques that provide real-time insights into their growth mechanisms. This review highlights recent progress in in-situ optical observation techniques, focusing on their application to thermal chemical vapor deposition (CVD) processes for graphene and TMDCs. Optical microscopy techniques, including radiation-mode microscopy (Rad-OM) and ultraviolet (UV) reflection microscopy, offers a significant advantage, as it can be applied under a wide range of conditions, including near-atmospheric pressure and high temperatures. These observations have deepened the understanding of critical factors such as precursor diffusion and catalyst interactions. By combining fundamental understanding with practical implementation, in-situ optical methods are considered promising approaches for realizing scalable and high-quality synthesis of 2D materials and for promoting their future industrial applications.