Triple ion beam sputtering deposition of beta-FeSi2

Semiconductor iron disilicide (beta-FeSi2) films were obtained by furnace annealing at 800 degrees C in inert atmosphere starting from ion beam sputtered Fe or cosputtered Fe+mSi (m=1 or 2) films deposited on Si(lll). In some case a low energy argon ion beam (100 eV) bombarded the growing film during the sputtering. The composition, the crystalline;structure and the optical and electrical behaviour of the films were studied. Results on iron silicide formation indicate that assistance bombardment is very effective in improving the composition uniformity of the films and in reducing the oxygen content into the films. Cosputtering allows to limit or avoid the huge silicon diffusion from the substrate changing the dynamic of silicide formation. All films present polycrystalline beta-FeSi2 structure with [202] or [220] preferential orientation of the silicide grains. Room temperature spectral transmittance data indicate a direct energy gap for all films in the range 0.82-0.85 eV. The values of room temperature electrical resistivity (congruent to 10(-1) Omega cm) and Hall mobility (15-40 cm(2)V(-1)s(-1)) measured are typical for polycrystalline beta-FeSi2 films