Structural and magnetic properties of ferromagnetic Fe1−xSix (0.18 ≤ x ≤ 0.33) films formed by rapid thermal annealing on silicon-on-insulator substrates

Abstract

We systematically investigate the structural and magnetic properties of ferromagnetic Fe1−xSix (0.18 ≤ x ≤ 0.33) films formed by rapid thermal annealing (RTA) on silicon-on-insulator (SOI) substrates. During RTA of an Fe film deposited on a SOI substrate (consisting of a top Si layer, a buried oxide SiO2 layer, and a Si substrate), an Fe1−xSix film is synthesized by the thermal reaction of the deposited Fe film and the top Si layer, but the reaction is limited by the buried oxide layer in the SOI substrate, thus the Si concentration x in Fe1−xSix can be controlled by both the initial thicknesses of the Fe film and the top Si layer. A variety of characteristics show that single-phase Fe1−xSix (x = 0.18, 0.22, and 0.25) films with D03 + B2 structure are successfully obtained by choosing the optimum annealing temperature and time. Furthermore, the ordering fraction of D03 and B2 structures in these films is found to be more than 87%, indicating that the crystalline quality of these films is comparable to that of bulk Fe1−xSix materials reported so far. On the other hand, it is found that the Fe1−xSix (x = 0.33) film has Fe3Si and FeSi phases as in the case of bulk Fe1−xSix with x = 0.33. The film production technique and the quality of the ferromagnetic Fe1−xSix presented in this study are very attractive and useful for silicon-based spintronic devices which are compatible with the complementary metal-oxide-semiconductor technology.