Optical properties of β-FeSi2 on Si (100) inclined substrate

beta-FeSi2 has been attracting a great deal of attention because of its compatibility with Si-based light-emitting diodes (LEDs). It has also been reported that beta-FeSi2 thin film undergoes a direct transition with a band gap of about 0.85 eV. However, some authors have reported that beta-FeSi2 has an indirect band gap structure on the basis of several first principles calculations. This difference is thought to be induced by the stress of the beta-FeSi2 interface acting on Si by lattice mismatch, which affects the band structure of the beta-FeSi2 thin film. To investigate the effect, we evaluated the optical properties of beta-FeSi2 grown on lattice matched Si (001) substrate 80 degrees off toward the (110) direction. All samples were formed by depositing Fe on the Si substrate to grow beta-FeSi2 thin film by electron beam deposition. From Raman measurements, it was observed that the samples prepared on inclined substrate shifted to higher wave numbers. From the optical absorption measurement, we observed that the band structure was changed by the Si off substrate. Additionally, the PL intensity at about 0.8 eV for the samples grown on the Si off substrate was increased.