Unique growth mode observed in a Pb thin film on the threefold surface of an i-Ag-In-Yb quasicrystal

Novel epitaxial quasicrystalline films can be grown using the surfaces of intermetallic quasicrystals as templates. Here, we present a study of Pb adsorption on the threefold i-Ag-In-Yb surface, where Pb grows in a manner contrasting with conventional thin-film growth modes. Pb atoms are found to adsorb at sites over a range of heights, which are explained by bulk atomic positions left vacant by surface truncation, producing three-dimensional, isolated quasicrystalline Pb structures. This finding is contrasted with the growth of Pb on the more commonly used fivefold surface of the same quasicrystal, where smooth epitaxial layers result. We suggest that this unique structure originates due to the lower atomic density of the threefold surface, compared to the fivefold surface. Similar atomic density can be found in lower symmetry planes of periodic systems, but these planes are often unstable and become facetted. This stable low-density quasicrystalline substrate provides a facile route to achieve this type of templated growth.