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 brief 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. Nevertheless, the problem in rising strictly monolayer WS2 resulting from its non-self-limiting development mechanism, might hinder its industrial improvement as a result of the uncontrollable development kinetics in achieving excessive uniformity in thickness and property on wafer-scale. On this work, we report a scalable course of to attain 4-inch wafer-scale fully-covered strictly monolayer WS2 by making use of the in-situ self-limited thinning of multilayer WS2 fashioned by sulfurization of WOx movies. By way of a pulsed provide of sulfur precursor vapor below a steady H2 move, 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 purposeful concept (DFT) calculations reveal that the self-limited thinning is arisen from the thermodynamic instability of WS2 prime layers versus steady backside monolayer WS2 on sapphire above a vacuum sublimation temperature of WS2. The self-limited thinning method not solely overcomes the intrinsic limitation of typical vapor-based development strategies in stopping 2nd layer WS2 area nucleation/development, but additionally presents further benefits corresponding to scalability, simplicity, and chance for batch processing, thus opening up a brand new avenue to develop a manufacturing-viable development know-how for the preparation of strictly-monolayer WS2 on wafer-scale.
