A quasi-1D surface alloy of silicon and silver, composed of pentagonal motifs

A surface alloy is a two-dimensional mixture of a metal with other elements that is confined within a few atomic layers on a surface. In the important case of silicon surface alloys, it has recently been predicted in the literature that a sub-monolayer deposition of silicon on a silver (001) surface leads to the formation of a surface alloy with interesting topological properties. In this paper, we have elucidated the atomic structure of the alloy formed: it is composed of planar double-pentagon motifs linked to form quasi-1D Si chains, stabilized by the presence of Ag atom pairs. This geometry was determined by a study combining theoretical (DFT) and experimental (STM, surface XRD) tools. The electronic structure associated with the surface alloy formed is in excellent agreement with ARPES measurements published in the literature. This work highlights the importance of considering the presence of pentagonal geometries in 2D materials and heterostructures, and of taking into account the formation of surface alloys to stabilize their formation.

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https://www.nature.com/articles/s41467-024-53589-4