Direct Synthesis of Locally Strained Monolayer WS ₂ by Chemical Vapor Deposition

The atomic thinness and mechanical flexibility of two-dimensional (2D) transition metal dichalcogenides (TMDs) make strain engineering a powerful strategy for tailoring their functional properties. Nevertheless, conventional strain-engineering methods often suffer from limited spatial control and unwanted sample damage. Here, we report a controlled synthesis of monolayer WS 2 with programmable localized strain via a sulfur-rich chemical vapor deposition approach. Atomic-resolution scanning transmission electron microscopy reveals varying degrees of atomic-level local strain, which lead to significant suppression of Raman, photoluminescence, and second-harmonic generation spectral intensities. Furthermore, piezoresponse force microscopy measurements demonstrate a characteristic butterfly-shaped amplitude loop accompanied by near-180° phase switching, indicative of robust ferroelectric behavior. Consistent hysteresis observed in vertical device architectures further confirms the emergence of out-of-plane ferroelectricity. Our work introduces a scalable, damage-free route to create tailored strain landscapes in monolayer TMDs, thereby opening avenues for property control in 2D semiconductors and enabling the design of multifunctional devices.