Epitaxy from the liquid phase: tuning metastable phases in Fe-Pd thin films by laser-assisted rapid solidification on substrates
Epitaxy by crystallization of thin liquid films on suitable substrates constitutes an alternative approach to molecular beam epitaxy, particularly if metastable phases are required. Employing laser-assisted rapid solidification, we demonstrate for the example of the body-centred-cubic, body-centred-tetragonal, face-centred-tetragonal and face-centred-cubic phases of Fe7Pd3 thin films, how the interplay of cooling rate and substrate-assisted nucleation affects the resulting metastable crystal phase and epitaxial relationship. Exemplarily employing lanthanum strontium aluminium tantalum oxide, MgO, and Si single crystals as substrates, this is experimentally demonstrated by an x-ray diffraction study and pole figure measurements. The underlying solidification kinetics are clarified using finite element calculations on the resulting time-temperature profile. Employing secondary ion mass spectroscopy we additionally demonstrate that the absence of interdiffusion is a central requirement for successful application.