Transmission electron microscopy study of intermetallic compound Fe3Al x Si1−x epitaxially grown on GaAs

Epitaxial growth of single crystal thin films of Fe₃Al_xSi_1−x intermetallic compounds on GaAs (001) substrates is carried out in a multi-chamber molecular beam epitaxy (MBE) system. Uniform thickness of the metal films and abrupt interfaces of the metal/GaAs are obtained. Interfacial misfit dislocations are observed in the as-grown Fe₃Al(15nm)/GaAs with the substrate temperature held at 250°C. The dislocation density resulting from strain relaxation is found to increase with film thickness. In contrast, a fully strained Fe₃Si layer 60nm thick has been obtained at a growth temperature as high as 500°C. Strain relaxation of Fe₃Si/GaAs interface is only observed in the samples grown at temperatures higher than 500°C or post-annealed at 500°C for an extensive period of time. High resolution X-ray diffraction and TEM observations show that a high quality ternary film, Fe₃Al_0.13Si_0.87, was grown on GaAs with a 0% lattice mismatch.