ANALYSIS OF INTERFACIAL REACTIONS OF FE FILMS ON MONOCRYSTALLINE GAAS

The reactions between monocrystalline GaAs(1 0 0) and thin polycrystal line Fe films have been investigated by application of conversion elec tron Mossbauer spectroscopy and high-resolution electron microscopy, T he presence of a thin amorphous intermixed layer at the Fe/GaAs interf ace in as-deposited samples is first pointed out. The reacted layer, 8 -10 nm thick, forms upon the native oxide of the GaAs substrate during the deposition process of the iron. The solid-state interdiffusions a re also studied in the temperature range 400-550 degrees C, They are s hown to produce a layered microstructure of the type Fe/Fe3GaCy (0 les s than or equal to y less than or equal to 0.5)/FexAs (x = 1, 2)/GaAs. The percentage of unmixed Fe atoms as well as the ferromagnetic and p aramagnetic Fe fractions are calculated at each stage of an isochronal kinetic which also shows that the reactions are diffusion controlled with an activation energy of 1.5 eV. The orientation relationships at the Fe2As/GaAs and FeAs/GaAs interfaces, as well as the average grain size in the Fe3GaCy sublayer, are also determined.