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Epitaxial growth of cobalt oxide phases on Ru(0001) for spintronic device applications

Olanipekun, Opeyemi and Ladewig, Chad and Kelber, Jeffry A. and Randle, Michael D. and Nathawat, Jubin and Kwan, Chun-Pui and Bird, Jonathan P. and Chakraborti, Priyanka and Dowben, Peter A. and Cheng, Tao and Goddard, W. A., III (2017) Epitaxial growth of cobalt oxide phases on Ru(0001) for spintronic device applications. Semiconductor Science and Technology, 32 (9). Art. No. 095011. ISSN 0268-1242. doi:10.1088/1361-6641/aa7c58.

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Cobalt oxide films are of technological interest as magnetic substrates that may support the direct growth of graphene, for use in various spintronic applications. In this work, we demonstrate the controlled growth of both Co_3O_4(111) and CoO(111) on Ru(0001) substrates. The growth is performed by Co molecular beam epitaxy, at a temperature of 500 K and in an O_2 partial pressure of 10^(−4) Torr for Co_3O_4(111), and 7.5 × 10^(−7) Torr for CoO(111). The films are distinguished by their dissimilar Co 2p x-ray photoemission (XPS) spectra, while XPS-derived O/Co stoichiometric ratios are 1.33 for Co3O4(111) and 1.1 for CoO(111). Electron energy loss (EELS) spectra for Co_3O_4(111) indicate interband transitions at ~2.1 and 3.0 eV, while only a single interband transition near 2.0 eV is observed for CoO(111). Low energy electron diffraction (LEED) data for Co_3O_4(111) indicate twinning during growth, in contrast to the LEED data for CoO(111). For Co_3O_4(111) films of less than 20 Å average thickness, however, XPS, LEED and EELS data are similar to those of CoO(111). XPS data indicate that both Co oxide phases are hydroxylated at all thicknesses. The two phases are moreover found to be thermally stable to at least 900 K in UHV, while ex situ atomic force microscopy measurements of Co_3O_4(111)/Ru(0001) indicate an average surface roughness below 1 nm. Electrical measurements indicate that Co_3O_4(111)/Ru(0001) films exhibit dielectric breakdown at threshold voltages of ~1 MV cm^(−1). Collectively, these data show that the growth procedures yield Co_3O_4(111) films with topographical and electrical characteristics that are suitable for a variety of advanced device applications.

Item Type:Article
Related URLs:
URLURL TypeDescription
Kelber, Jeffry A.0000-0002-3259-9068
Dowben, Peter A.0000-0002-2198-4710
Cheng, Tao0000-0003-4830-177X
Goddard, W. A., III0000-0003-0097-5716
Additional Information:© 2017 IOP Publishing Ltd. Received 12 May 2017. Accepted 28 June 2017. Accepted Manuscript online 28 June 2017. Published 17 August 2017. Work at UNT was supported by was supported by the NSF under grant no. ECCS-1508991, and in part by C-SPIN, a funded center of STARnet, a Semiconductor Research Corporation (SRC) program sponsored by MARCO and DARPA under task IDs 2381.001 and 2381.006. Work at Buffalo was supported by the NSF under grant. No. ECCS-1509221. Work at UNL was supported by the NSF under grant No. ECCS-1508541. Work at Caltech was supported was supported by the NSF (DMR-1436985) and DOE (DE-SC0014607).
Funding AgencyGrant Number
Microelectronics Advanced Research Corporation (MARCO)UNSPECIFIED
Defense Advanced Research Projects Agency (DARPA)2381.001
Defense Advanced Research Projects Agency (DARPA)2381.006
Department of Energy (DOE)DE-SC0014607
Subject Keywords:cobalt oxide, graphene, spintronics, magneticoxides, molecular beam epitaxy
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Issue or Number:9
Record Number:CaltechAUTHORS:20170818-081948581
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Official Citation:Opeyemi Olanipekun et al 2017 Semicond. Sci. Technol. 32 095011
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:80598
Deposited By: Ruth Sustaita
Deposited On:18 Aug 2017 17:27
Last Modified:15 Nov 2021 19:37

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