Abstract
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 SiOx on Si substrate. The epitaxial Fe3O4 layer on Si substrates enable us the integration of highly functional spintoronic devices with Si technology.
Highlights
In the field of spintronics, spin injection and transport phenomena have attracted much attention owing to the possibility of producing novel functional devices1–3
Magnetic oxides possess unique properties11–14; Fe3O4 or (LaSr) MnO3 have a half-metallic state, which provides highly spin polarized current15, and NiFe2O4 or CoFe2O4 are magnetic insulators, which means that they could work as a spin filter tunnel barrier16–18. γ-Fe2O3 is another candidate as the spin filter barrier
After treatment of the Si substrate, we confirmed that the in-situ reflection high energy electron diffraction (RHEED) pattern of the Si substrate had a (7 × 7) streak pattern (Supplementary Fig. S1)
Summary
In the field of spintronics, spin injection and transport phenomena have attracted much attention owing to the possibility of producing novel functional devices. The spin injection technique, in which the spin-polarized currents are injected from ferromagnetic metals into conventional semiconductor materials , has been intensely investigated for the preparation of spintronic devices. Magnetic oxides possess unique properties; Fe3O4 or (LaSr) MnO3 have a half-metallic state, which provides highly spin polarized current, and NiFe2O4 or CoFe2O4 are magnetic insulators, which means that they could work as a spin filter tunnel barrier. Γ-Fe2O3 is another candidate as the spin filter barrier It is the spinel type ferrimagnetic insulator that is obtained by over oxidation of Fe3O419. Fe3O4 is the ferrimagnetic conducting oxide with spinel crystal structure. From the viewpoint of the crystal structure, Fe3O4 and γ-Al2O3 seems to grow on Si epitaxially
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