Ion channeling and x-ray diffraction studies of epitaxial Fe on GaAs(001)

Epitaxial 80-nm-thick films of Fe were grown at room temperature by molecul ar beam epitaxy on GaAs(001) and on a reacted layer composed of a mixture o f (Fe2As+Fe3Ga1.8As0.2) resulting from the solid-state interdiffusions in a (20 nm Fe)/GaAs(001) structure annealed at 450 degrees C. The partially re laxed strains induced by the lattice mismatch were studied using ion channe ling, Rutherford backscattering, and x-ray diffraction. Both channeled angu lar scans and x-ray diagrams showed that the 80 nm Fe films are not fully r elaxed. The average crystalline quality of the Fe films is better on GaAs(0 01) (chi(min)=3%) than on the reacted layer (chi(min)=7%) mainly because of the mosaic structure of the reacted layer. The strains parallel to the sur face in the Fe films were found to be compressive in the Fe/GaAs(001) heter ostructure and tensile in the Fe/(Fe2As+Fe3Ga1.8As0.2)/GaAs(001) one. There fore, our work shows that the presence of a reacted layer at the interface in a Fe/GaAs structure does not impede the epitaxial growth of Fe but can i nvert the kind of strain appearing in the Fe film. (C) 1999 American Instit ute of Physics. [S0021-8979(99)02122-2].