On the growth of Fe2As grains at the interface of the Fe/AlxGa1−xAs (x = 0.25) system

Abstract Iron thin films on ion-etched monocrystalline AlGaAs(0 0 1) substrates were prepared using ion-beam sputtering deposition. The interface reaction was characterised by planar and cross-sectional transmission electron microscopy after annealing in vacuum at 400°C for 1 h. Interdiffusion mainly results in the generation of Fe 2 As grains growing into the substrate, perpendicular to the Fe/AlGaAs interface. The iron-arsenide grains exhibit an either triangular or trapezoidal shape. Analyses on their morphology and size, as well as on the orientation relationships between Fe 2 As and AlGaAs phases were also carried out. The appearance of the Fe 2 As phase is discussed in terms of standard enthalpy for alloy formation. Finally a pyramidal growth model is proposed for Fe 2 As grains, which mainly involves the four close-packed {1 1 1}AlGaAs planes.