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

Abstract

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.