Approach to form planar structures based on epitaxial Fe-1 - Si-x(x) films grown on Si(111)

An approach to form planar structures based on ferromagnetic Fe_1 − xSi_x films is presented. Epitaxial Fe_1 − xSi_x iron‑silicon alloy films with different silicon content (x = 0–0.4) were grown on Si(111) substrates. Structural in situ and ex situ characterization of the films obtained was made by X-ray diffraction, reflective high-energy electron diffraction, Rutherford backscattering spectrometry and transmission electron microscopy, which confirmed single crystallinity and interface abruptness for all films. Etching rates in the wet etchant (HF: HNO₃: H₂O = 1: 2: 400) for the films with various chemical composition were obtained. A nonmonotonic dependence of the etching rate on silicon content with a maximum for the composition Fe_0.92Si_0.08 was discovered. Moreover, the etching process is vertical and selective in the etching solution, i.e., the etching process takes place only in silicide film and does not affect substrate. As an example, a four-terminal planar structure was made of Fe_0.75Si_0.25/Si(111) structure using the etching rate obtained for this silicon content. Magneto-optical Kerr effect (MOKE) microscopy and transport properties characterization indicated successful etching process.