A study of Au adsorption on yttrium disilicide nanowires on Si (001) substrate from first principles*

Core-shell nanoclusters with Au coating layer on uniformly dispersed rear-earth disilicide nanowires are very promising for various applications such as nanocatalysis. Using the first principles approach, we studied the structure and electronic properties of a single Au atatom on yttrium disilicide nanowires on the Si(100) substrate. A series of possible adsorption sites were explored and we found that the ``hollow'' site on the YSi2 nanowire is the most preferential one, where the Au adatom binds to two Si atoms and an Y atom underneath. The most stable site for Au on Si(001) is the ``cave'' site, but the binding energy is 0.11 eV higher than that on the wire. This indicates that the Au atoms tend to aggregate toward nanowires, which leads to growth of core-shell metallic structures. Electrons deplete from Au adatom and accumulated in regions between Au and Si. The chemical activity of Au/YSi2 will be discussed in light of charge density, density of states and adsorption energy of CO molecules.