Fabrication of iron disilicide from multilayer by helicon plasma sputtering

Helicon plasma sputtering of Fe/Si multilayer followed by thermal annealing in Ar atmosphere was used to fabricate β-FeSi2 films. [Fe 0.5nm/Si 1.6nm] 120 multilayer was deposited on Si（100） substrate and then the samples were annealed at 900℃ for 2h or at 9001000℃ for 10s. Annealed samples were characterized by X-ray diffractometry（XRD）, Rutherford backscattering spectroscopy, scanning electron microscopy and optical absorption measurement. （202）/（220） oriented β-FeSi2 films are fabricated from the multilayer according to XRD patterns. It is found that there is a very small redistribution of Fe and Si components in the films during the thermal annealing, so that a good stoichiometry of FeSi2 can be obtained. It is also revealed by scanning electron microscopy that multilayer technology can result in a smooth surface for β-FeSi2 films. Optical absorption spectra demonstrate that the films have a direct band gap of 0.9eV at room temperature.