Polarization-Guided Spiral Growth of Chiral Copper Sulfide: From Design Rules to Tunable Chiroptics.

Polarization-directed spiral growth has emerged as a powerful route to chiral microstructures with promising applications in chiral photonics, optoelectronics, catalysis, and biosensing. However, the material requirements for spiral formation have remained unclear, limiting the rational design of such structures. Here, we systematically investigate polarization-directed photoelectrochemical deposition of different metal sulfides across multiple substrates with different laser wavelengths. We discover two sequential requirements: efficient photoelectrochemical electron transfer from the substrate (via hot electrons or photoelectrons) enables initial nucleation, while intrinsic crystal anisotropy with polarization-aligned transition dipoles drives spiral growth. Using this framework, we achieved size-tunable fabrication of spiral Cu2-xS metastructures, which exhibit wide-range tailorability in circular differential scattering and vortical dichroism scattering. This work provides a predictive framework for designing chiral semiconductor metastructures with tailorable chiroptical response, applicable to a broad range of anisotropic materials beyond copper sulfide.