Intrinsically Patterned Two-Dimensional Transition Metal Halides

Patterning and defect engineering are key methods for tuning the properties and enabling distinctive functionalities in two-dimensional (2D) materials. However, generating 2D periodic patterns of point defects in 2D materials, such as vacancy lattices that can serve as antidot lattices, has been elusive until now. Herein, we report on 2D transition metal dihalides epitaxially grown on metal surfaces featuring periodically assembled halogen vacancies that result in alternating coordination of the transition metal atom. Using low-temperature scanning probe microscopy and low-energy electron diffraction, we identified the structural properties of intrinsically patterned FeBr₂ and CoBr₂ monolayers grown epitaxially on Au(111). Density functional theory reveals that Br vacancies are facilitated by low formation energies, and the formation of a vacancy lattice results in a substantial decrease in the lattice mismatch with the underlying Au(111). We demonstrate that interfacial strain engineering presents a versatile strategy for controlled patterning in two dimensions with atomic precision over several hundred nanometers to solve a long-standing challenge of growing atomically precise antidot lattices. In particular, patterning of 2D materials containing transition metals provides a versatile method to achieve unconventional spin textures with noncollinear spin.