Synthesis and Properties of Semiconducting Iron Disilicide β-FeSi2

Abstract

Beta-iron disilicide β-FeSi2 bulk crystals were prepared by a horizontal gradient freeze method. The grown β-FeSi2 bulk crystals were characterized by structural, electrical and optical measurements. The β-FeSi2 single phase was determined by X-ray diffraction measurements. The electrical resistivity of β-FeSi2 increased exponentially with decreasing temperature. From optical absorption spectra that were obtained from transmittance measurements, the energy band gap was determined to be 0.85 eV. The refractive index, extinction coefficient and dielectric constants were calculated using optical reflectance spectra by Kramers-Kronig analysis. In addition to β-FeSi2 bulk materials, β-FeSi2 films were prepared on Si(100) substrates by a laser ablation method using the above β-FeSi2 bulk crystals as target materials. Strong Raman signals from the β-FeSi2 films were observed at 171 cm-1, 190 cm-1, 199 cm-1 and 247 cm-1, indicating deposition of well-oriented high-quality films. The optical absorption coefficient at 1.0 eV and energy band gap were determined to be 1.99× 105 cm-1 and 0.85 eV, respectively.