Ion-beam irradiation effect on solid-phase growth of β-FeSi2

Effects of Ar+ ion-beam irradiation on solid-phase growth of beta-FeSi2 have been investigated. Fe (10 nm)/Si structures were irradiated with 25 keV Ar+ (5.0 x 10(15) cm(-2)) at a temperature of 25degreesC (sample A) or 400degreesC (sample B), and subsequently annealed at 800degreesC. A reference was obtained after annealing without irradiation (sample C). X-ray diffraction results indicated that beta-FeSi2 was formed after annealing at 800degreesC for 5 h, and the formation rate was the fastest for sample A and the slowest for sample C, i.e., A > B much greater than C. However, Auger electron spectroscopy measurements showed that atomic mixing at Fe/Si interface before annealing was B > A much greater than C. These results suggested that amorphization of Si substrate, in addition to atomic mixing, enhanced the solid-phase growth of beta-FeSi2, which was confirmed experimentally. Moreover, a direct band gap of 0.89 eV was observed for the sample with pre-amorphization by the Fourier-transform infrared (FT-IR) spectroscopy measurements. These enhancement effects were attributed to that the phase transition to beta-FeSi2 was accelerated by atomic arrangement induced during annihilation of excess vacancies. These enhancement effects can be utilized for nano-fabrication of beta-FeSi2 by using focused ion-beam irradiation. (C) 2002 Published by Elsevier Science B.V.