Space-Confined CVD Synthesis of 2D Single-Crystalline Tellurium Oxychloride

Abstract Two-dimensional (2D) metal oxyhalides provide a unique platform for investigating complex multi-field coupling, intrinsic polarization, and physical anisotropy. However, current research in this field remains predominantly limited to transition-metal and rare-earth systems, leaving alternative crystal structures unexplored, particularly those featuring main-group metal or semimetal cations. Here, we report the space-confined chemical vapor deposition (CVD) synthesis of 2D single-crystalline Te6O11Cl2, a main-group tellurium oxychloride. By suppressing the material’s intrinsic bulk growth, the space-confined configuration directs the synthesis toward a preferential (001) orientation, producing highly uniform stoichiometric single crystals on various substrates. Such geometric confinement drives an anisotropic growth mode that favors lateral extension over vertical thickening, resulting in flakes with lateral sizes up to 97 μm and thicknesses down to 8.3 nm. The low-symmetry framework of Te6O11Cl2, featuring highly anisotropic bonding configurations and heavy-atom lattices, dictates its in-plane vibrational anisotropy and an ultra-broad optical transparency window spanning from 0.3 to 25 μm. Optical and electrical measurements reveal that Te6O11Cl2 possesses a wide bandgap of 3.85 eV, a high dielectric constant of 19.1, and a low leakage current density of ∼10−7 A cm−2 prior to breakdown. This study introduces an open-framework main-group paradigm into the 2D oxyhalide material family, providing a potential candidate material for designing next-generation anisotropic electronic and optoelectronic devices.