Controllable Chemical Vapor Deposition Synthesis and Second-Harmonic Generation of Rhombohedral Cr2S3.

Non-layered two-dimensional (2D) chromium-based chalcogenides have garnered significant attention due to their distinctive magnetic, electronic, and optical properties. In this work, we report the controllable synthesis of high-quality rhombohedral Cr2S3 nanosheets on mica substrates via an atmospheric pressure chemical vapor deposition (CVD) strategy. The as-grown rhombohedral Cr2S3 nanosheets exhibit pronounced optical second-harmonic generation (SHG) signals, which show thickness-dependent enhancement and a strong dependence on both the linear excitation and detection polarization configurations. Most notably, temperature-dependent SHG measurements reveal a distinct inflection point near the Néel temperature (TN ≈ 120 K), where the SHG intensity exhibits a sharp enhancement upon cooling below TN. This behavior arises from the additional magnetic dipole contributions activated by magnetic ordering, establishing SHG as a sensitive probe of magnetic phase transitions in non-layered 2D magnetic materials. Furthermore, circularly polarized SHG signals exhibit nearly 100% circular polarization at low temperatures. This work systematically elucidates the nonlinear optical response characteristics of rhombohedral Cr2S3 and their correlation with magnetic ordering transitions, laying an experimental foundation for the application of 2D non-van der Waals magnetic materials in nonlinear optoelectronics and spin-optoelectronic devices.