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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 the monolayer WS2 additionally makes it extremely promising for future high-performance optoelectronics. Nonetheless, the issue in strictly rising monolayer WS2, as a consequence of its non-self-limiting progress mechanism, could hinder its industrial improvement due to the uncontrollable progress kinetics in achieving the excessive uniformity in thickness and property on the wafer-scale. On this examine, we report a scalable course of to attain a 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. By way of a pulsed provide of sulfur precursor vapor beneath a steady H2 circulate, 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 useful principle (DFT) calculations reveal that the self-limited thinning arises from the thermodynamic instability of the WS2 high layers versus a secure backside monolayer WS2 on sapphire above a vacuum sublimation temperature of WS2. The self-limited thinning strategy overcomes the intrinsic limitation of standard vapor-based progress strategies in stopping the twond layer WS2 area nucleation/progress. It additionally gives extra benefits, corresponding to scalability, simplicity, and chance for batch processing, thus opening up a brand new avenue to develop a manufacturing-viable progress expertise for the preparation of a strictly-monolayer WS2 on the wafer-scale.
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