In situ diffraction studies of the initial growth processes of textured icosahedral quasicrystalline thin films

The seeding and morphology of quasicrystalline Ti{sub x}Ni{sub y}Zr{sub 1-x-y} thin films grown by pulsed-laser deposition on Al{sub 2}O{sub 3}(0001) have been investigated in situ, using in-plane x-ray diffraction and reflectivity with synchrotron radiation. The crystallinity of the final films was further studied ex situ using a laboratory x-ray source. Local icosahedral order becomes established after a film thickness of 1.5 nm, which is followed by an abrupt change in the growth rate after a film thickness of approximately 5 nm, as long-range quasicrystalline order begins to become energetically favorable. The films grow two-dimensionally even up to thicknesses of over 100 nm and are highly textured, consisting of columnar grains with one of their fivefold symmetry axes perpendicular to the substrate surface.