Selective Growth of Decagonal Ai-Co Thin Films By Reactive Diffusion: Kinetic and Thermodynamic Aspects

We report on the formation by reactive diffusion of a pure decagonal quasicrystalline film in Al/Co bilayer and multilayer structures of overall composition Al 13 CO 4 . We show that this method is highly selective since several stable phases which exist around this composition are never observed. the quasicrystal is not the first reaction product but is obtained as a second reaction step by a peritectoid reaction between Al 9 Co 2 and the remaining cobalt. DSC analysis allows the determination of both the enthalpy of formation of the decagonal quasicrystal (ΔH f = -31500 ± 2000 J/g-atom) and its activation energy of growth (2.6 ± 0.5 eV).