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Epitaxial integration of the highly spin-polarized ferromagnetic semiconductor EuO with silicon and GaN

Abstract

Doped EuO is an attractive material for the fabrication of proof-of-concept spintronic devices. Yet for decades its use has been hindered by its instability in air and the difficulty of preparing and patterning high-quality thin films. Here, we establish EuO as the pre-eminent material for the direct integration of a carrier-concentration-matched half-metal with the long-spin-lifetime semiconductors silicon and GaN, using methods that transcend these difficulties. Andreev reflection measurements reveal that the spin polarization in doped epitaxial EuO films exceeds 90%, demonstrating that EuO is a half-metal even when highly doped. Furthermore, EuO is epitaxially integrated with silicon and GaN. These results demonstrate the high potential of EuO for spintronic devices.

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Figure 1: In-plane magnetic properties of 130-nm-thick Eu1−yLayO1−x films with y=0, 0.005 and 0.01 grown on (110) YAlO3.
Figure 2: Electronic transport properties of 130-nm-thick Eu1−yLayO1−x films with y=0 and 0.005 grown on (110) YAlO3.
Figure 3: Andreev reflection measurements on a Eu0.995La0.005O1−x/Nb contact.
Figure 4: X-ray diffraction scans of Si-capped EuO1−x films (typical thickness 130 nm) grown on (001) Si and (0001) GaN.

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Acknowledgements

A.S. thanks the Alexander von Humboldt Foundation for a research fellowship. The work at Penn State was supported by the Office of Naval Research (ONR) through grants N00014-03-1-0721 and N00014-04-1-0426 monitored by Colin Wood. The work at the University of Augsburg was supported by the BMBF (13N6918), the EU (Nanoxide), the DFG (SFB484) and the ESF (THIOX). The work at Montana State was supported by NSF EEC-0303774 and ONR through contract N00014-03-1-0692. Y.B. acknowledges support from the Russian Foundation for Basic Research through grant 05-02-17175. L.F.K. and D.A.M. acknowledge support under the ONR EMMA MURI monitored by Colin Wood and by the Cornell Center for Materials Research (NSF DMR–0520404 and IMR-0417392). L.F.K. acknowledges financial support by Applied Materials. The Advanced Light Source is supported by the Department of Energy.

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Correspondence to Darrell G. Schlom.

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Schmehl, A., Vaithyanathan, V., Herrnberger, A. et al. Epitaxial integration of the highly spin-polarized ferromagnetic semiconductor EuO with silicon and GaN. Nature Mater 6, 882–887 (2007). https://doi.org/10.1038/nmat2012

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