One-Step Chemical Vapor Deposition of High-Quality γ-CuI Films Using Copper Iodide Cubane Clusters as the Single-Source Precursor and Growth Mechanism on the Size-Matched Surface

γ-CuI with zinc blende structure has emerged as a next-generation electrical material, but its current two-step chemical vapor deposition (CVD) method still faces problems including high I-residue/vacancy and low film uniformness. The strategy of one-step CVD using a single-source precursor (SSP) could be a feasible solution. In this work, a tetra-nuclear cubane cluster Cu4I4(TMOP)4 (TMOP = tris(4-methoxyphenyl)phosphine) was constructed and used as SSP in γ-CuI deposition first. As indicated by structural analysis of this SSP, the introduction of methoxy on the p-position of PPh3 and the absence of π–π/C–H···π interactions can improve its solubility in organic solvent. More importantly, cuprophilic interactions and fluctuant Cu–I bonds can be beneficial for fracture and reconstitution on the substrate surface during the CVD process. Upon optimization of the substrate, deposition sites, gas velocities, and deposition temperatures, the continuous γ-CuI film with an ultralow roughness (Rq = 4.60 nm) under optimal CVD conditions has been obtained, which has been characterized by XRD, SEM, AFM, XPS, and Raman spectra. The {111} preferential growth mechanism of this γ-CuI has been clarified: the anchoring of Cu4I4 clusters by the size-matched SnO2(110) surface, the Cu–I fracture/reconstitution restricted by cuprophilic interactions, and final growth along the {111} direction. This one-step CVD process using the copper iodide cubane cluster as SSP could pave a new way for the large-scale production of high-quality γ-CuI films.