AVS 50th International Symposium
    Magnetic Interfaces and Nanostructures Thursday Sessions
       Session MI+SC-ThM

Paper MI+SC-ThM7
Materials Characterization and Magnetic Studies of Epitaxial Co@sub x@Ti@sub 1-x@O@sub 2-x@ Deposited on Si(001) by Molecular Beam Epitaxy

Thursday, November 6, 2003, 10:20 am, Room 316

Session: New Spintronic Materials
Presenter: T.C. Kaspar, University of Washington
Authors: T.C. Kaspar, University of Washington
T. Droubay, Pacific Northwest National Laboratory
A.C. Tuan, University of Washington
C.M. Wang, Pacific Northwest National Laboratory
S.A. Chambers, Pacific Northwest National Laboratory
J.W. Rogers, Jr., Pacific Northwest National Laboratory
Correspondent: Click to Email
For spintronic devices such as spin-FETs, efficient injection of spin-polarized electrons into a semiconductor material is necessary. Progress has been made using ferromagnetic metals to tunnel spin-polarized electrons into AlGaAs/GaAs quantum well structures. However, for devices compatible with current semiconductor technology, efficient spin injection into Si is desired. Diluted magnetic semiconductors (DMSs) that can be grown epitaxially on Si are prime candidates. The epitaxial growth will result in a high-quality interface, reducing depolarization caused by scattering at interfacial defects. Further, the conductivity of the DMS can be tuned by doping to match that of Si, greatly increasing the spin injection efficiency. While most known DMS materials have Curie points well below room temperature, anatase Co@sub x@Ti@sub 1-x@O@sub 2-x@ has been shown to have a Curie temperature of at least 700K when deposited on LaAlO@sub 3@(001). In addition, anatase is well lattice-matched to Si. To prevent interfacial reactions between the film and substrate resulting in SiO@sub 2@ and/or silicide formation, a buffer layer of epitaxial SrTiO@sub 3@ (STO) is first deposited. In this study, a STO buffer layer and Co@sub x@Ti@sub 1-x@O@sub 2-x@ film on Si(001) are deposited by molecular beam epitaxy (MBE), which has been shown previously to result in higher quality Co@sub x@Ti@sub 1-x@O@sub 2-x@ films than pulsed laser deposition (PLD). Magnetic films have been successfully deposited with Co in the +2 charge state. The growth mode of Co@sub x@Ti@sub 1-x@O@sub 2-x@ has been investigated to minimize the formation of Co-rich anatase particles on the film surface. Thorough materials characterization of the Si interface, the STO buffer layer, and the Co@sub x@Ti@sub 1-x@O@sub 2-x@ film will be presented, paying particular attention to the possibility of metallic Co atoms in the film. In addition, the electronic and magnetic properties of the structure will be presented.