Fabrication of Epitaxial Fe₃O₄ Film on a Si(111) Substrate

The application of magnetic oxides in spintronics has recently attracted much attention. The epitaxial growth of magnetic oxide on Si could be the first step of new functional spintronics devices with semiconductors. However, epitaxial spinel ferrite films are generally grown on oxide substrates, not on semiconductors. To combine oxide spintronics and semiconductor technology, we fabricated Fe₃O₄ films through epitaxial growth on a Si(111) substrate by inserting a γ-Al₂O₃ buffer layer. Both of γ-Al₂O₃ and Fe₃O₄ layer grew epitaxially on Si and the films exhibited the magnetic and electronic properties as same as bulk. Furthermore, we also found the buffer layer dependence of crystal structure of Fe₃O₄ by X-ray diffraction and high-resolution transmission electron microscope. The Fe₃O₄ films on an amorphous-Al₂O₃ buffer layer grown at room temperature grew uniaxially in the (111) orientation and had a textured structure in the plane. When Fe₃O₄ was deposited on Si(111) directly, the poly-crystal Fe₃O₄ films were obtained due to SiO_x on Si substrate. The epitaxial Fe₃O₄ layer on Si substrates enable us the integration of highly functional spintoronic devices with Si technology.