Growth and structure of L10 ordered FePt films on GaAs(001)

The structural properties of epitaxial L1(0) ordered FePt(001) films, grown by molecular beam epitaxy, (alternating deposition of Fe and Pt atomic layers) on buffer-Pt/seed-Fe/GaAs(001) have been studied by in situ reflection high-energy electron diffraction and by ex situ x-ray scattering as a function of the growth conditions. Reflection high-energy electron diffraction intensity oscillations measured during FePt layer growth provide evidence for island growth at T-s = 200 degreesC and quasi layer-by-layer growth at T-s = 350 degreesC. From small-angle and wide-angle x-ray scattering it was found that the degree of epitaxy depends critically on morphology of the seed layer and the substrate roughness. X-ray diffraction analysis showed that the long-range order parameter increases from near zero for films grown at 200 degreesC to 0.65 for films grown at 350 degreesC. This confirms the fact that the order parameter is mainly determined by the surface mobility of the atoms which is controlled experimentally by the substrate temperature.