Nucleation and growth of Ag films on a quasicrystalline AlPdMn surface

Nucleation and growth of thin films of Ag on the fivefold surface of an Al₇₂Pd19.5Mn8.5 icosahedral quasicrystal is studied with scanning-tunneling microscopy. For low coverages, flux-independent island nucleation is observed involving adatom capture at ``traps.'' With increasing coverage, islands start growing vertically, but then spread, and ultimately form hexagonal nanocrystals. These have fcc symmetry and pyramidlike multilayer stacking along the 〈111〉 direction. The constituent hexagonal islands have five different orientations, rotated by 2{π}/5, thus reflecting the symmetry of the substrate.