Ultralow-Temperature Synthesis of Two-Dimensional Anisotropic FeOCl and Quasi-One-Dimensional Moiré Superlattices

Two-dimensional (2D) materials, with an atomic thickness and exceptional properties, hold great promise for next-generation devices and flexible electronics. However, these applications face integration challenges due to high-temperature synthesis and transfer-induced degradation. Here, we demonstrate the ultralow-temperature growth of high-quality 2D FeOCl, enabling its direct integration into heterostructures and flexible substrates. The synthesized 2D FeOCl exhibits high crystallinity, uniformity, and intrinsic structural and optical anisotropy. Using this method, we synthesized FeOCl-based vertical heterostructures on both layered 2D MoS2 and nonlayered 2D Fe3O4. The heterostructures exhibit highly ordered quasi-one-dimensional moiré superlattices and anisotropic second harmonic generation (SHG) patterns. Theoretical calculations attribute these properties to anisotropic charge redistribution at the interfaces. This work establishes a versatile low-temperature platform for synthesizing and integrating 2D materials, providing both a pathway for polarization-sensitive optoelectronics and spintronic devices and a scalable synthetic route to explore emergent one-dimensional (1D) quantum physics.