Tin-mediated phase-controlled growth of γ-InSe thin films on Si (100) via molecular beam epitaxy

• Sn-mediated MBE growth enables phase-selective γ-InSe on Si (100) • Sn reduces Se surface coverage, promoting γ-InSe over γ-In 2 Se 3. • XPS/ToF-SIMS confirm Sn-free films, ruling out direct incorporation. • DFT shows SnSe desorbs easily, preventing accumulation on growth front. • The growth method enables scalable γ-InSe integration for optoelectronic devices. Indium selenide is a III-VI semiconductor with promising electronic and optoelectronic properties, but its polymorphism makes single phase growth difficult, hindering its use in advanced electronic and photonic devices. In this study, we introduce a novel phase-selective growth of γ-InSe using tin (Sn)-mediated Molecular Beam Epitaxy (MBE) on Si (100). By tuning Sn flux during indium and selenium co-evaporation, we demonstrate a phase transition from γ-In 2 Se 3 to γ-InSe. X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) confirm the absence of Sn within the grown films, indicating that Sn irradiation facilitates the displacement of Se adatoms from the surface, effectively lowering the effective Se/In flux ratio. This reduction favors the formation of γ-InSe over γ-In 2 Se 3 as confirmed by Raman spectroscopy, mimicking the effect of reduced Se supply. Density functional theory calculations showed that SnSe clusters have lower formation energies than InSe clusters, indicating that Sn preferentially binds with Se. Furthermore, SnSe clusters exhibit weaker adsorption on the Si (100) surface compared to InSe clusters, suggesting that SnSe desorbs more readily. These findings offer new insights into surfactant-mediated phase engineering and pave the way for the scalable integration of single-phase γ-InSe on silicon for future electronic and optoelectronic applications.