Tailoring Iron Nanostructures on MoS 2 : The Pivotal Role of Sulfur Vacancies in Growth Morphology and Charge Transfer

The interaction of Fe with MoS 2 monolayers supported on Au(111) is investigated by combining scanning tunneling microscopy, synchrotron‐based photoemission spectroscopy, resonant photoemission (ResPES), x‐ray absorption spectroscopy (XAS), and density functional theory (DFT) calculations. On pristine MoS 2 , room‐temperature Fe deposition produces three‐dimensional nanoparticles (NPs) consistent with a Volmer–Weber growth mode, driven by dominant Fe‐Fe cohesive energy over Fe‐substrate adhesion. Charge transfer from the metallic NPs to the MoS 2 film is evidenced by rigid core‐level shifts in both Mo 3 d and S 2 p photoemission spectra, while ResPES and XAS data confirm a Fe 2+ ‐like character at the Fe/MoS 2 interface, attributed to a core@shell architecture. On defect‐engineered MoS 2 , sulfur vacancies act as preferential trapping sites suppressing Fe surface diffusion, stabilizing sub‐nanometric clusters with average lateral dimensions below 1 nm. In this regime, the spectroscopic changes observed at undercoordinated Mo sites upon Fe deposition are attributed primarily to a redistribution of vacancy‐induced charge rather than to formal Mo reoxidation, as confirmed by DFT Bader charge analysis of the Fe cluster‐vacancy complex. Taken together, DFT simulations and photoemission data establish sulfur vacancies as key determinants of Fe growth morphology and interfacial charge redistribution, with direct implications for the rational design of transition‐metal‐functionalized 2D supports.