Optical properties of semiconducting iron disilicide thin films

Iron disilicide thin films were prepared by furnace reaction of ion beam sputtered iron layers with single-crystal silicon wafers and with low-pressure chemical vapor deposition (LPCVD) polycrystalline silicon thin films. X-ray diffraction indicates the films are single-phase, orthorhombic, β-FeSi2. Impurity levels are below the detection limit of Auger spectroscopy. Normal incidence spectral transmittance and reflectance data indicate a minimum, direct energy gap of 0.87 eV. The apparent thermal activation energy of the resistivity in the intrinsic regime is about half of this minimum optical gap. With such a direct band gap, the material may be suitable for the development of both light-sensitive and light-emitting thin-film devices within the silicon microelectronics technology.