Fabrication of β-FeSi 2/Si composite films for photovoltaic applications by using scanning annealing

Abstract

For use as superior photovoltaic materials, thin β-iron silicide (β-FeSi 2) nanoparticles/Si composite films were fabricated by using rf-magnetron sputtering and post scanning annealing. After the scanning annealing at a preheating temperature of 800 °C, transmission electron microscopy (TEM) observation was then used to confirm 10–50-nm nanoparticles in FeSi 2=8.4 at% composite films. Amorphous and single-phase FeSi 2 films were also crystallized by the scanning annealing to determine the type of crystal phase of the nanoparticles. Lower preheating temperature (<800 °C) yielded β-FeSi 2 films, whereas higher preheating temperature (>900 °C) yielded α-FeSi 2 films. TEM observation and X-ray diffraction (XRD) analysis confirmed the successful fabrication of β-FeSi 2 nanoparticles/Si composite films. In conclusion, the photoabsorbance of thin Si films at wavelengths between 500 and 800 nm was significantly enhanced by fabrication with β-FeSi 2. The photoabsorption spectra could be controlled by changing the diameter of the nanoparticles. The nanoparticle diameter depended on the deposition conditions and the preheating temperature.