Gradient-Mass-Transfer Synthesis of 2D [Bi₂CuO₃]SO₄ Crystals for Anisotropy Engineering

The intrinsic physical anisotropy of low-symmetry materials makes them highly promising candidates for polarization-sensitive devices. However, their practical application remains constrained by the scarcity of single materials that can combine low symmetry with high performance. Here, we report a novel low-symmetry [Bi₂CuO₃]SO₄ crystal with an insulating nature, designed to enable symmetry control over conventional high-performance semiconductors. We achieve controllable growth of layered [Bi₂CuO₃]SO₄ nanosheets via a gradient-mass-transfer-assisted chemical vapor deposition method, with thicknesses down to 1.43 nm. Alternating [Bi₂CuO₃]²⁺ cationic layers and SO₄ ^2- anionic layers, coupled with disparate ionic radii of Bi³⁺ and Cu²⁺, endow the [Bi₂CuO₃]SO₄ material with low structural symmetry, resulting in pronounced in-plane optical anisotropy. Upon integration with high-symmetry MoS₂, [Bi₂CuO₃]SO₄ induces interfacial symmetry breaking, driven by strong interfacial coupling and substantial charge redistribution. Notably, by fabricating devices along different crystallographic orientations of [Bi₂CuO₃]SO₄, tunable polarization ratios are exhibited, reaching a maximum of 5.44 along the a-axis and a minimum of 1.57 along the b-axis. This work establishes a reliable strategy for obtaining heterostructures with low symmetry and tunable anisotropy, advancing next-generation directional optoelectronic devices.