Chirality-transferred epitaxy of circular polarization-sensitive ReS2 monolayer single crystals

The epitaxial growth of semiconducting two-dimensional (2D) materials is vital to achieve wafer-scale single-crystalline films for beyond-silicon electronics. However, gaining full control over both in-plane and out-of-plane orientations (i.e., lateral crystal alignments and chirality) is particularly challenging when growing low-symmetry 2D single crystals. Here, using triclinic ReS2 semiconductor monolayers as a model system, we demonstrate the chirality-controlled epitaxial growth of unidirectional, anisotropic single crystals on an insulating chiral surface via the synergy of terraces, steps, and kinks, yielding >97.5% chirality selectivity and >99% in-plane orientation consistency. The products display an anisotropic ratio of 1.9 in photodetection (comparable to exfoliated samples) and high distinguishability of circularly polarized light. Theoretical calculations combined with a set of microscopy and spectroscopy methods show that terrace facets determine the epitaxial growth direction, while steps and kinks break the degeneracy of ReS2 in the lateral orientation and chirality. This approach is also applicable to the chiral epitaxy of other low-symmetry 2D single crystals, like monoclinic MoO2. Our method extends the range of control over 2D material growth, enabling chirality transfer from the substrate to the crystal, and promotes the large-area synthesis of chirality-selected, single-crystal 2D materials.