Tailored Synthesis of Heterogenous 2D TMDs and Their Spectroscopic Characterization.

Two-dimensional (2D) vertical van der Waals heterostructures (vdWHs) show great potential across various applications. However, synthesizing large-scale structures poses challenges owing to the intricate growth parameters, forming unexpected hybrid film structures. Thus, precision in synthesis and thorough structural analysis are essential aspects. In this study, we successfully synthesized large-scale structured 2D transition metal dichalcogenides (TMDs) via chemical vapor deposition using metal oxide (WO 3 and MoO 3 ) thin films and a diluted H 2 S precursor, individual MoS 2 , WS 2 films and various MoS 2 /WS 2 hybrid films (Type I: Mo x W 1-x S 2 alloy; Type II: MoS 2 /WS 2 vdWH; Type III: MoS 2 dots/WS 2 ). Structural analyses, including optical microscopy, Raman spectroscopy, transmission electron microscopy (TEM) with energy-dispersive X-ray spectroscopy, and cross-sectional imaging revealed that the A 1g and E 2g modes of WS 2 and MoS 2 were sensitive to structural variations, enabling hybrid structure differentiation. Type II showed minimal changes in the MoS 2' s A 1g mode, while Types I and III exhibited a ~2.8 cm -1 blue shift. Furthermore, the A 1g mode of WS 2 in Type I displayed a 1.4 cm -1 red shift. These variations agreed with the TEM-observed microstructural features, demonstrating strain effects on the MoS 2 -WS 2 interfaces. Our study provides insights into the structural features of diverse hybrid TMD materials, facilitating their differentiation through Raman spectroscopy.