Metal vapour vacuum arc ion implantation to synthesize FeSi2 layers on Si(100) and Si(111)

Abstract

Using a metal vapour vacuum arc (MEVVA) ion source, high current Fe ion implantations directly into Si or through an iron film deposited on Si wafers are carried out at an extraction voltage of 40 kV with a current density from 65 to 152 μA cm -2 at a nominal dose from 3 x 10 17 to 3 x 10 18 cm -2 . For the directly implanted Si wafers, at a fixed dose of 4 x 10 17 cm -2 , a semiconducting β-FeSi 2 layer gradually grows with increasing current density. The unique semiconductivity of the formed β-FeSi 2 layer is evidenced by the measured Hall mobility being in the range of 60 to 100 cm2/Vs. Implanting with the current density of 152 μA cm -2 , the β-FeSi 2 transforms into a metallic α-FeSi 2 phase with a sheet resistance of 42 Ω/ □ at a nominal dose of 3 x 10 18 cm -2 . For the Si wafers with deposited Fe film, β-FeSi 2 is also formed by Fe ion implantation. Post-implantation annealing of the implanted samples provides some useful information for the understanding of the formation mechanism, which is discussed in terms of the simultaneous thermal annealing caused by beam heating during implantation.