Atomically-thin monolayer WS2 is a promising channel materials for next-generation Moore’s nanoelectronics owing to its excessive theoretical room temperature electron mobility and immunity to quick channel impact. The excessive photoluminescence (PL) quantum yield of monolayer WS2 making them extremely promising for continued scaling of optoelectronics even past the diffraction restrict. Nonetheless, the problem in rising strictly monolayer WS2 attributable to its non-self-limiting development mechanism, might hinder its industrial improvement as a result of the uncontrollable development kinetics achieve excessive uniformity in thickness and property on wafer-scale. On this work, we report a scalable course of to realize 4-inch wafer-scale fully-covered strictly monolayer WS2 by making use of the in-situ self-limited thinning of multilayer WS2 shaped by sulfurization of WOx movies. Via a pulsed provide of sulfur precursor vapor underneath a steady H2 movement, the self-limited thinning course of can successfully trim down the overgrown multilayer WS2 to the monolayer restrict with out damaging the remaining backside WS2 monolayer. Density practical idea (DFT) calculations reveal that the self-limited thinning is arisen from the thermodynamic instability of WS2 high layers versus secure backside monolayer WS2 on sapphire above a vacuum sublimation temperature of WS2. The self-limited thinning strategy not solely overcomes the intrinsic limitation of standard vapor-based development strategies in stopping 2nd layer WS2 area nucleation/development, but additionally gives extra benefits reminiscent of scalability, simplicity, and risk for batch processing, thus opening up a brand new avenue to develop a manufacturing-viable development expertise for the preparation of strictly-monolayer WS2 on wafer-scale.