Alkali chalcogenides-assisted vapor-liquid-solid growth of WX₂ (X = S, Se, Te)

Promoter-assisted chemical vapor deposition (CVD) has emerged as a robust strategy for the low-temperature synthesis of diverse transition metal dichalcogenides (TMDs). In these processes, promoter-induced intermediates facilitate specific reaction pathways, enabling controlled growth via vapor-solid-solid (VSS) or vapor-liquid-solid (VLS) modes. While previous studies have primarily focused on transition metal precursors, growth pathways involving engineered chalcogen-based intermediates remain underexplored due to their volatility and low melting points. Here, we demonstrate a stabilized chalcogen strategy that enables the scalable growth of highly crystalline tungsten-based (W-) TMDs through the formation of alkali-chalcogen mixtures within the VLS regime. Atomically resolved scanning tunneling microscopy (STM) of transferred WTe₂ confirms ultraclean surfaces, attributed to the salt-like alkali-chalcogen interfacial layer that enables support-free film delamination. This work demonstrates a versatile route toward the scalable synthesis and clean manipulation of high-quality TMD.