Structure of AuSi nanoparticles on Si(111) from reflection high-energy electron diffraction and scanning tunneling microscopy

Gold-rich Au _x Si_1−x particles grown on Si(111)7 × 7 are studied by reflection high-energy electron diffraction (RHEED) and scanning tunneling microscopy (STM). The diffraction patterns reveal that (1) at least two different crystal structures coexist on the substrate; (2) the most prominent data correspond to a rhombohedral or quasi closed-packed structure; and (3) the particles show formation of an unusual contact facet to the substrate. Complete crystal alignment of the particles to the substrate lattice is found with no hints of random orientation. The findings are compared to STM images in terms of their structure, orientation, and morphology.