Semiconducting amorphous FeSi2 layers synthesized by co-sputter deposition

We report here on the synthesis of semiconducting amorphous FeSi2 layers by co-sputter deposition of Fe and Si on silicon (100) wafers. The layers were grown to a thickness of 300-400 nm, at various substrate temperatures. Structural characterisation has shown that the deposited layers have the FeSi2 stoichiometry and are fully amorphous up to a deposition temperature of 200 degreesC. Optical absorption measurements have demonstrated that the amorphous FeSi2 layers have semiconducting properties, with a direct band gap of 0.89-0.90 eV at room temperature (RT). In order to relax the amorphous structure, some samples were irradiated with 200 keV Ar ions. It was found that both an increased deposition temperature and/or ion irradiation induce a higher photo-absorption, which was attributed to establishing a medium range order in the amorphous phase. The applied fabrication routine can be highly efficient for potential applications of this material in large area electronics and for production of solar cells. (C) 2004 Published by Elsevier B.V.