Bonding-imposed crystallization of 1D nanostructures based on a luminescent and anisotropic 2D van der Waals crystal

Physical states in nanoscale solids are tied to their crystalline order, morphology, and size. However, deterministically accessing different nanocrystal morphologies from a single phase usually involves complex synthetic routes, catalysts, or multi-step lithographic techniques. Here, we demonstrate the catalyst-free synthesis of nanosheets and nanowires based on the luminescent 2D van der Waals (vdW) phase, GaTe, as a model phase that manifests atomic precision and a highly anisotropic quasi-1D substructure. We program the size and morphology of the resulting nanostructures by varying the relative rates of precursor deposition and diffusion, achieving dense, uniform, and widespread growth. Ultrathin nanowires resulting from this synthesis exhibit strikingly enhanced low-temperature luminescence with narrow near-infrared (NIR) emission bandwidths. These spectral characteristics arise from defect-bound states confined within a nanowire morphology that acts as a deep sub-wavelength optical cavity, making them suitable as optical emitters with small footprints either as stand-alone structures or coupled with other vdW crystals.