Annealing effects on structures and morphologies of Fe/Si coreshell clusters

Transmission electron microscopy, X-ray diffraction and electrical resistivity have been observed for annealed Fe/Si coreshell clusters and their assemblies in comparison with those for annealed Fe and Si clusters. Fe clusters are wholly oxidized, where voids are formed in the central regions. Si clusters are not wholly oxidized, keeping a diamond-like structure, where voids are scarcely formed in the central regions because the initially-oxidized surfaces play roles of passive layers and protect the cores from oxidations. In FeSi core/Si shell clusters, SiOX thin layers are also formed on Si shell surfaces, protecting Si shells and FeSi cores from further oxidations. FeSi core regions maintain a bcc structure, where no ordered phase is detected probably due to the chemical heterogeneity among these clusters and the surface segregation of Si atoms. Excess vacancies are accumulated to become voids between FeSi cores and Si-shells.