Excitonic transitions in β-FeSi2 epitaxial films and single crystals

摘要: Photoreflectance spectra were obtained from an epitaxial film and a bulk single crystal of β-FeSi2 at low temperatures (T⩽180 K). A model based on the results low-temperature absorption [M. Rebien et al., Appl. Phys. Lett. 74, 970 (1999)] was used to describe main features spectra. In agreement with results, transitions corresponding ground state first excited free exciton observed in both crystal. However, additional subband gap are revealed photoreflectance thin film. It is suggested that these may be related impurity or transition plus bound resonance. From analysis taken film, over temperature range 12–180 K, we extract binding energy (0.009±0.002) eV direct T=0 K (0.934±0.002) eV.