FORMATION OF POLYCRYSTALLINE BETA-FESI2 LAYERS BY ION-IMPLANTATION AND THEIR OPTICAL-PROPERTIES

Polycrystalline beta-FeSi2 was made by ion beam synthesis (IBS) using implantation of Fe+ ions into Si. Results from two-step annealing (2SA ) and three-step annealing (3SA) processes are discussed. X-ray diffra ction data exhibited that for 3SA samples, beta-FeSi2 is grown at spec ific annealing conditions, whereas it is always formed for 2SA samples . The formation of beta-FeSi2 layer with thickness of 59-79 M1 was con firmed by Rutherford backscattering measurements. The 3SA-sample showe d a direct band-gap energy (E-E) of 0.88 eV and 0.80 eV for the 2SA sa mple. In the 2 K photoluminescence spectra, two emissions at 0.786-0.8 08 eV were ascribed to beta-FeSi2. Similar features were obtained for beta-FeSi2 crystals prepared by horizontal gradient freeze and electro n beam deposition (EBD) methods. p-Type beta-FeSi2 layers were fabrica ted on n-type Si (100) substrates by Mn+ ion-implantation into EBD-gro wn beta-FeSi2 layers and subsequent annealing. (C) 1998 Elsevier Scien ce S.A. All rights reserved.