THE MICROSTRUCTURE OF FE AND AG THIN-FILMS GROWN BY MOLECULAR-BEAM EPITAXY ON GAAS (001)

The interfaces and microstructures in molecular-beam epitaxy grown iron and silver films on GaAs(001) have been investigated using high-resolution transmission electron microscopy. Stacking faults were observed in silver films deposited directly on the GaAs (type A films: Ag(500 Å)/GaAs), but not in those which included a six monolayer Fe prelayer between the Ag and the GaAs (type B films: Ag(500 Å)/Fe(6 ml)/GaAs). The introduction of this prelayer reduces the misalignment between the Ag film and GaAs substrate lattices and leads to improved epitaxial quality. In a third structure, which retained the prelayer but to which was added an overlayer of iron (type C films: Fe(500 Å)/Ag(500 Å)/Fe(6 ml)/GaAs), stacking faults were once again found. With the Fe layer between the Ag film and GaAs substrate (type B and C films) the (001) plane of Ag was parallel to the (001) plane of the Fe film and the (001) plane of GaAs substrate but with the Ag lattice rotated 45°about the [001] axis relative to the substrate. Without the Fe prelayer (type A film), the (11̄0) plane of Ag was parallel to the (001) plane of the GaAs substrate. The orientation relationships were [001]Ag parallel to [110]GaAs and [110]Ag parallel to [11̄0] GaAs.