Correlation between structural and optical properties of ion beam synthesized beta-FeSi2 precipitates in Si

The structural and optical properties of beta-FeSi2 precipitates produced by ion beam synthesis have been investigated by transmission electron microscopy, photoluminescence (PL) analysis and near infrared transmission measurements. The PL spectrum of beta-FeSi2 precipitates in a dislocation free sample has been observed to consist of a sharp line at 1.54 mu m and a weak peak at 1.46 mu m. Optical transmission measurements showed a direct band gap about 0.8 eV, smaller than in continuous beta-FeSi2 film. Calculation of the electronic bands of beta-FeSi2 for different values of the lattice parameters indicates that this reduction can be ascribed to band distortion provided by the lattice strain.