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.

Graphical abstract