Evidence for Step-Edge-Assisted Large Hole Borophene on Ni(111)

Due to its unique electronic properties, boron tends to form various multicenter bonds, enabling the construction of diverse two-dimensional borophene structures through modulation of the number and distribution of boron vacancies within a triangular lattice. In this study, we investigate a large-hole borophene model on heated Ni(111) substrates via molecular beam epitaxy under ultra-high-vacuum conditions. The complex atomic arrangement and electronic structures were investigated by scanning tunneling microscopy, low-energy electron diffraction, angle-resolved photoemission spectroscopy, and density functional theory calculations. Our results suggest that boron atoms are initially incorporated into the Ni surface and preferentially nucleated at step edges. The favorable geometric matching between the proposed structure and the Ni step-edge configuration contributes to the stabilization of the structure and facilitates its formation under the present growth conditions. These findings broaden the structural diversity of 2D borophene sheets and offer insights into the controlled synthesis of complex borophene architectures on metallic substrates.