Structure determination of the ordered (2 × 1) phase of NiSi surface alloy on Ni(111) using low-energy electron diffraction

Abstract

The (2 × 1) structure of the two-dimensional nickel silicide surface alloy on Ni(111) was investigated using quantitative low-energy electron diffraction analysis. The unit cell of the determined silicide structure contains one Si and one Ni atom, corresponding to a chemical formula of NiSi. The Si atoms adopt substitutional face-centered cubic hollow sites on the Ni(111) substrate. The Ni–Si bond lengths were determined to be 2.37 and 2.34 Å. Both the alloy surface and the underlying first layers of Ni atoms exhibit slight corrugation. The Ni–Si interlayer distance is smaller than the Ni–Ni interlayer distance, which indicates that Si atoms and underlying Ni atoms strongly interact.