Phase Tailoring of In₂Se₃ Toward van der Waals Vertical Heterostructures via Selenization of γ-InSe Semiconductor

The polymorphic nature of In₂Se₃ leads to excellent phase-dependent physical properties including ferroelectricity, photoelectricity, and especially the intriguing phase change ability, making the precise phase modulation of In₂Se₃ of fundamental importance but very challenging. Here, the growth of In₂Se₃ with desired-phase is realized by temperature-controlled selenization of van der Waals (vdW) layered bulk γ-InSe. Detailed results of Raman spectroscopy, scanning electron microscopy (SEM), and state-of-the-art spherical aberration-corrected transmission electron microscopy (Cs-TEM) clearly and consistently show that β-In₂Se₃, 3R α-In₂Se₃, and 2H α-In₂Se₃ can be perfectly obtained at ≈270, ≈300, and ≈600 °C, respectively. Further comprehensive atomic imaging analyses confirm that the seeding material, InSe, plays a critical role in the low-temperature epitaxial growth of vdW-layered In₂Se₃, and, more interestingly, β-In₂Se₃ acts as an intermediate phase between 3R and 2H α-In₂Se₃ transitions. This investigation not only provides a simple yet versatile strategy for the phase modulation of In₂Se₃, but also sheds light on the temperature-dependent phase evolution of In₂Se₃.