Optical characterization of β-FeSi2 thin films prepared on fused quartz by femtosecond laser ablation

Single-phase β-FeSi2 thin films have been grown on quartz substrates using femtosecond laser deposition (800 nm, 50 fs, 1 KHz) under gas pressure of 3.0×10−4 Pa. X-ray diffraction (XRD) and field-emission scanning electron microscopy (SEM) were used to determine the structural properties and surface images of the films. Typical XRD patterns of the film showed that no other diffraction peak except β-FeSi2 was found. The SEM results indicated that the films were composed of well-distributed grains, in the range 50–150 nm in diameter. In addition, normal incidence spectral transmittance and reflectance data suggested that the β-FeSi2 film has a direct energy gap of about 0.85 eV. The thickness of the layer and the refractive index of the film were determined by performed calculation in the wavelength range 1.9–2.7 μm. Furthermore, the Raman spectra of the films were also discussed.