Formation of Twisted Copper Phosphide on Cu(111) Surface Predicted by Machine Learning Simulations

ABSTRACT The fundamental interactions at surfaces and interfaces dictate the thermodynamic and kinetic pathways in the epitaxial growth of two‐dimensional (2D) materials. The atomic‐scale evolution of phosphorus (P) on Cu(111) serves as a representative example of interfacial complexity, where dynamic reconstructions and competing chemical interactions obscure the underlying growth mechanisms. In this study, we combine a rigorously trained Cu–P machine learning force field with atomically resolved scanning tunneling microscopy to resolve the reaction of P on Cu(111) at atomic scale. Our results demonstrate that phosphorene is neither thermodynamically favorable nor kinetically accessible on Cu(111). Instead, strong Cu‐P bonding drives the substitutional incorporation of P into the topmost Cu layer, forming a twisted copper phosphide (Cu 2 P) surface alloy – a phase that thermodynamically competes phosphorene over the experimentally relevant coverage regime. Formation of this Cu 2 P layer generates interfacial strain that organizes into a straight reconstruction network and transforms into spiral configurations upon annealing. With increasing P coverage, three‐dimensional (3D) P islands, rather than flat phosphorene, are formed on Cu 2 P surface. These findings resolve a long‐standing controversy regarding P growth on Cu(111) and highlight the crucial role of interfacial interaction between the precursor and the substrate in 2D material growth.