Kinetics control of bilayer WSe2 growth for high-performance transistors by precursor modulation

The development of high-performance p-type two-dimensional (2D) semiconductors ( e.g. , WSe 2 ) is critical for complementary electronics beyond silicon-based technology. While bilayer WSe 2 , indicates superior electrical potential over its monolayer counterpart, owing to reduced contact resistance and suppressed Fermi-level pinning, its scalable synthesis remains challenging due to uncontrolled nucleation and limited understanding of vertical growth mechanisms. Herein, elucidate the atomic-scale pathway of bilayer WSe 2 growth in a molten salt-assisted chemical vapor deposition (CVD) process. Density functional theory (DFT) calculations reveal that WO 2 Cl 2 intermediates promote vertical stacking by cooperatively adsorbing on monolayer template centers, while W 1 Se 1 clusters facilitate epitaxial nucleation. By precisely controlling the Se/WO₃ vapor ratio, we achieve the epitaxial growth of uniform equal-bilayer (EB) WSe 2 with high crystallinity and clean interfaces. Back-gated transistors based on EB- WSe 2 exhibit a high on/off ratio of 10⁷ and a hole mobility of 50.1 cm²V⁻¹s⁻¹ , significantly outperforming the monolayer devices with 14.7-fold enhancement. This work provides a mechanistic foundation for the controlled synthesis of 2D heterostructures and advances the application of 2D semiconductors in post-Moore electronics.