Epitaxial film growth of Au-Al alloy on a quasiperiodic surface of icosahedral Al₇₂Pd_19.5Mn_8.5

We have found that an epitaxial film of Au-Al alloy can be formed on a quasiperiodic surface of icosahedral Al₇₂Pd_19.5Mn_8.5. Depositions of Au onto the quasiperiodic surface, which is perpendicular to one of the fivefold axes of Al₇₂Pd_19.5Mn_8.5. were attempted in order to create a quasicrystal of a single element as an epitaxial film. Although the desired film was not obtained on the clean surface, an ordered layer of Au-Al alloy with icosahedral symmetry was formed in the presence of predeposited In, which worked as a surfactant. X-ray photoelectron diffraction (XPD) images for Au 4f and Al 2s emissions from the ordered layer indicate clear fivefold symmetric patterns which are coherent with the symmetry of the substrate. In addition, symmetric elements specific to the icosahedral symmetry are clearly recognized in these patterns, indicating that both Au and Al atoms are located in an icosahedral environment with long-range bond-orientational order.