Application of the CALPHAD method for the prediction of amorphous phase formation

Structure and Thermodynamics of Amorphous Ti-Si Produced by Solid-State Interdiffusion

The thermodynamic and structural aspects of amorphous titanium silicide formation by solid-state reaction have been addressed. The radial distribution function of an amorphous Ti60Si40 reaction product has been determined by electron diffraction. It is an amorphous metallic alloy, with a coordination number of about 11.4, and a local arrangement of atoms which is similar to that in a crystalline silicide, Ti5Si4. The free energy of the amorphous alloy as a function of composition has been determined from the heats of crystallization of co-deposited amorphous Ti-Si alloys, and the heat of formation of the amorphization product as measured by differential scanning calorimetry (DSC). The latter was measured to be 35 ± 5 kJ/mole. Using these data, free energy of the amorphous Ti-Si phase has been calculated by applying the CALPHAD method. These results are discussed in light of the mechanism and energetics of the amorphization reaction.

Pulsed Laser Deposition of Thin Metallic Multilayers and Amorphous Films

The method of pulsed excimer laser ablation using KrF radiation was applied for the deposition of thin metallic elementary multilayers. Above an ablation threshold of about 5 J/cm2 an ‘explosive’ evaporation of the metallic targets occurs leading to high deposition rates of up to 5 nm/s. For different metals, the ablation threshold slightly varies leading at the same laser fluence to different growth rates as shown for Ag, Fe, Zr and Nb. By using two elementary targets and adjusting the dwelling times on both targets, Fe/Ag, Fe/Zr and Fe/Nb multilayers of different bilayer thicknesses were deposited. While Fe/Ag superstructures show crystalline phases down to a periodicity of 1 nm, Fe/Zr and Fe/Nb films are amorphous at such wavelengths. On the other side, Fe/Nb multilayers can also be amorphized by a solid state interdiffusion reaction of the elementary multilayers. The surfaces of the grown films are smooth except for a small number of droplets on the film surface.