The formation and thermal stability of ion-beam-synthesized ternary Me xFe 1− xSi 2 (Me=Co, Ni) in Si(111)

Abstract

Buried Co x Fe 1− x and Ni x Fe 1− x silicides were prepared by consecutive metal implantation in Si(111). Transmission-electron microscopy analysis shows strong evidence for the formation of metastable ternary Co 0.5Fe 0.5Si 2 and Ni 0.5Fe 0.5Si 2 precipitates during implantation, the lattice structure of which is believed to be mainly B-type oriented (twinned) CaF 2. Annealing of the samples at 1000°C results in coalescence of the silicide into continuous layers with sharp interfaces. During this high-temperature treatment, nearly full phase separation occurs in the case of Co 0.5Fe 0.5Si 2, whereas for Ni 0.5Fe 0.5Si 2 only the onset of phase separation is observed. Channeling spectrometry indicates a good alignment of the silicides with the substrate. Furthermore, all samples were studied with X-ray diffraction and Mössbauer spectrometry, in order to obtain detailed information on the strain and the phases present.