Encyclopedia of 2D <i>β′</i> ‐In ₂ Se ₃ Growth Using Chemical Vapor Deposition: The Effects of Synthesis Parameters Onto Material Quality

Two‐dimensional (2D) In 2 Se 3 is a polymorphic layered semiconductor offering switchable ferroic and electronic functionalities, but scalable and reproducible synthesis of phase‐pure, thickness‐uniform films remains challenging because growth conditions often trigger polymorph coexistence and uncontrolled multilayering. Here we develop an InI + Se chemical vapor deposition route enabled by a modified reactor geometry incorporating an inner quartz liner that stabilizes vapor transport and improves reproducibility. By systematically mapping growth temperature, InI loading, Se sublimation temperature, carrier‐gas flow, and dwell time, we establish clear process–morphology relationships spanning isolated monolayer domains and millimeter‐scale coalesced monolayer films, with second‐layer islands, multilayer stacks, and bulk‐like growth emerging beyond the optimal growth window, as resolved by optical microscopy and atomic force microscopy. Raman spectra acquired from multiple substrate regions retain the characteristic β′ ‐In 2 Se 3 fingerprint across all parameter series, with no features attributable to other In 2 Se 3 polymorphs. Electron diffraction collected over widely separated regions supports long‐range crystallographic coherence of the single crystalline β′ parent lattice while resolving symmetry‐related orientations of the nanostriped superstructure. Together, the modified reactor design and parameter maps identify an operating window for phase‐pure, continuous, thickness‐uniform 2D β′ ‐In 2 Se 3 films, providing a practical foundation for scalable synthesis and device‐oriented studies.