STRUCTURAL AND OPTICAL CHARACTERIZATION OF BETA-FESI2 LAYERS ON SI FORMED BY ION-BEAM SYNTHESIS

Structural and optical properties have been investigated for surface b eta-FeSi2 layers on Si(100) and Si(111) formed by ion beam synthesis u sing Fe-56 ion implantations with three different energies (140-50 keV ) and subsequent two-step annealing at 600 degrees C and up to 915 deg rees C. Rutherford backscattering spectrometry analyses have revealed Fe redistribution in the samples after the annealing procedure, which resulting in a Fe-deficient composition in the formed layers. X-ray di ffraction experiments confirmed the existence of beta-FeSi2 by anneali ng up to 915 degrees C, whereas the phase transformation from the beta to alpha phase has been induced at 930 degrees C. In photoluminescenc e measurements at 2 K, both beta-FeSi2/Si(100) and beta-FeSi2/Si(111) samples, after annealing at 900-915 degrees C for 2 h, have shown two dominant emissions peaked around 0.836 eV and 0.80 eV, which nearly co incided with previously reported PL emissions from the sample prepared by electron beam deposition. Another beta-FeSi2/Si(100) sample has sh own sharp emissions peaked at 0.873 eV and 0.807 eV. Optical absorptio n measurements at room temperature have revealed the allowed direct ba ndgap of 0.868-0.885 eV as well as an absorption coefficient of the or der of 10(4) cm(-1) near the absorption edge for all samples.