Phase-Selective\nSynthesis of Rhombohedral WS<sub>2</sub> Multilayers by Confined-Space\nHybrid Metal–Organic Chemical\nVapor Deposition

Rhombohedral polytype transition metal dichalcogenide\n(TMDC) multilayers\nexhibit non-centrosymmetric interlayer stacking, which yields intriguing\nproperties such as ferroelectricity, a large second-order susceptibility\ncoefficient χ<sup>(2)</sup>, giant valley coherence, and a bulk\nphotovoltaic effect. These properties have spurred significant interest\nin developing phase-selective growth methods for multilayer rhombohedral\nTMDC films. Here, we report a confined-space, hybrid metal–organic\nchemical vapor deposition method that preferentially grows 3R-WS<sub>2</sub> multilayer films with thickness up to 130 nm. We confirm\nthe 3R stacking structure via polarization-resolved second-harmonic\ngeneration characterization and the 3-fold symmetry revealed by anisotropic\nH<sub>2</sub>O<sub>2</sub> etching. The multilayer 3R WS<sub>2</sub> shows a dendritic morphology, which is indicative of diffusion-limited\ngrowth. Multilayer regions with large, stepped terraces enable layer-resolved\nevaluation of the optical properties of 3R-WS<sub>2</sub> via Raman,\nphotoluminescence, and differential reflectance spectroscopy. These\nmeasurements confirm the interfacial quality and suggest ferroelectric\nmodification of the exciton energies.