IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Electronics Wednesday Sessions
       Session EL+MI-WeM

Paper EL+MI-WeM9
MBE Growth and Properties of Co-doped TiO@sub 2@ Anatase

Wednesday, October 31, 2001, 11:00 am, Room 111

Session: Spintronics III: Ferromagnetic Semiconductors
Presenter: S.A. Chambers, Pacific Northwest National Laboratory
Authors: S.A. Chambers, Pacific Northwest National Laboratory
S. Thevuthasan, Pacific Northwest National Laboratory
D. McCready, Pacific Northwest National Laboratory
R.F.C. Farrow, IBM Almaden Research Center
R.F. Marks, IBM Almaden Research Center
L. Folks, IBM Almaden Research Center
N. Ruzycki, Tulane University
D.L. Ederer, Tulane University
U. Diebold, Tulane University
Correspondent: Click to Email
The realization of fully functional spintronics requires semiconductors that are magnetic at ambient temperature. In a recent publication@footnote 1@, Co-doped anatase TiO@sub 2@ (Co@sub x@Ti@sub 1-x@O@sub 2@) epitaxial films grown on SrTiO@sub 3@(001) and LaAlO@sub 3@(001) by laser ablation were shown to exhibit weak ferromagnetism at room temperature for x up to 0.08. We have grown Co@sub x@Ti@sub 1-x@O@sub 2@ by oxygen-plasma-assisted molecular beam epitaxy on SrTiO@sub 3@(001) and SrAlLaO@sub 4@(001) substrates, for which the lattice mismatches are -3.1% and -0.8%, respectively. Preliminary results have confirmed that this material can be ferromagnetic at room temperature. Kerr effect measurements on some samples show larger remanence (>40%) than that seen in fig. 3 of ref. 1. In all cases, reflection high-energy electron diffraction measured during growth reveals that the film surface becomes progressively more disordered with increasing thickness, with secondary phases and/or complete disordering occurring after several tens of nm. X-ray diffraction reveals the presence of rutile in some cases. X-ray photoemission and x-ray absorption spectroscopy carried out at the LBNL Advanced Light Source reveal that Co is extremely mobile in the anatase lattice, and in most cases has a tendency to concentrate in the near-surface region. In addition, these spectroscopies reveal that Co in the ferromagnetic films is nearly 100% Co(II), whereas a mix of Co(II) and Co(III) is found in nonmagnetic films. Hall effect and TEM measurements are being carried out at the time of abstract preparation, and will be discussed at the conference. These preliminary results reveal that the single largest obstacle to reproducibility is the extremely facile diffusion of Co in the anatase lattice. @FootnoteText@ @footnote 1@Y. Matsumoto, M. Murakami, T. Shono, T. Hasegawa, T. Fukumura, M. Kawasaki, P, Ahmet, T. Chikyow, S.-Y. Koshihara, and H. Koinuma, Science, 291, 854 (2001).