Real‐Time Monitoring of 2D TMDC MOCVD: An In Situ Spectroscopic Reflectance Approach

Metal–organic chemical vapor deposition (MOCVD) has become a well‐established technique to grow 2D transition metal dichalcogenide (TMDC) materials on large scale with high reproducibility. Despite a steady progress in understanding the microscopic growth mechanisms, the lack of a dedicated in situ monitoring technique complicates the development and optimization of MOCVD processes for 2D TMDC materials, especially regarding a robust layer number control. In this work, a novel and industrially applicable approach is presented based on in situ spectroscopic reflectance measurements that can provide valuable real‐time insights into MOCVD processes. By analyzing the dynamics of reflectance spectra (350–810 nm) during deposition processes, the lateral growth and coalescence of (WSe 2 , MoS 2 , and WS 2 ) monolayers can be clearly identified from dynamic differential reflectance colormaps. Characteristic spectroscopic features of distinct TMDC thin films (especially WSe 2 ) of various thicknesses at different temperatures are analyzed and reported in detail, which can serve as an empirical reference to flexibly control and terminate growth at a certain targeted thickness. The proposed method can be potentially engineered into a real‐time data acquisition and processing tool, which can significantly contribute to the industrial fabrication of 2D TMDC thin films and heterostructures.