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 b y ion beam synthesis have been investigated by transmission electron micros copy, photoluminescence (PL) analysis and near infrared transmission measur ements. The PL spectrum of beta-FeSi2 precipitates in a dislocation free sa mple has been observed to consist of a sharp line at 1.54 mu m and a weak p eak at 1.46 mu m. Optical transmission measurements showed a direct band ga p 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 para meters indicates that this reduction can be ascribed to band distortion pro vided by the lattice strain. (C) 1999 Elsevier Science B.V. All rights rese rved.