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Title: Interfacial stability of ultrathin films of magnetite Fe 3 O 4 (111) on Al 2 O 3 (001) grown by ozone-assisted molecular-beam epitaxy

Authors:
 [1];  [2];  [3]; ORCiD logo [4];  [3]
  1. Advanced Photon Source, Argonne National Laboratory, 9700 S. Cass Ave., Argonne, Illinois 60439, USA
  2. Materials Science Division, Argonne National Laboratory, 9700 S. Cass Ave., Argonne, Illinois 60439, USA
  3. Department of Physics, University of Illinois, 1110 West Green Street, Urbana, Illinois 61801, USA
  4. Materials Science Division, Argonne National Laboratory, 9700 S. Cass Ave., Argonne, Illinois 60439, USA, Department of Materials Science and Engineering, KAIST, Daejeon 34141, South Korea
Publication Date:
Sponsoring Org.:
USDOE
OSTI Identifier:
1361731
Grant/Contract Number:
AC02- 06CH11357; FG02-07ER46383
Resource Type:
Journal Article: Publisher's Accepted Manuscript
Journal Name:
Applied Physics Letters
Additional Journal Information:
Journal Volume: 110; Journal Issue: 2; Related Information: CHORUS Timestamp: 2018-02-14 09:22:05; Journal ID: ISSN 0003-6951
Publisher:
American Institute of Physics
Country of Publication:
United States
Language:
English

Citation Formats

Hong, Hawoong, Kim, Jongjin, Fang, Xinyue, Hong, Seungbum, and Chiang, T. -C.. Interfacial stability of ultrathin films of magnetite Fe 3 O 4 (111) on Al 2 O 3 (001) grown by ozone-assisted molecular-beam epitaxy. United States: N. p., 2017. Web. doi:10.1063/1.4973808.
Hong, Hawoong, Kim, Jongjin, Fang, Xinyue, Hong, Seungbum, & Chiang, T. -C.. Interfacial stability of ultrathin films of magnetite Fe 3 O 4 (111) on Al 2 O 3 (001) grown by ozone-assisted molecular-beam epitaxy. United States. doi:10.1063/1.4973808.
Hong, Hawoong, Kim, Jongjin, Fang, Xinyue, Hong, Seungbum, and Chiang, T. -C.. Mon . "Interfacial stability of ultrathin films of magnetite Fe 3 O 4 (111) on Al 2 O 3 (001) grown by ozone-assisted molecular-beam epitaxy". United States. doi:10.1063/1.4973808.
@article{osti_1361731,
title = {Interfacial stability of ultrathin films of magnetite Fe 3 O 4 (111) on Al 2 O 3 (001) grown by ozone-assisted molecular-beam epitaxy},
author = {Hong, Hawoong and Kim, Jongjin and Fang, Xinyue and Hong, Seungbum and Chiang, T. -C.},
abstractNote = {},
doi = {10.1063/1.4973808},
journal = {Applied Physics Letters},
number = 2,
volume = 110,
place = {United States},
year = {Mon Jan 09 00:00:00 EST 2017},
month = {Mon Jan 09 00:00:00 EST 2017}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1063/1.4973808

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  • Thin films of iron oxides including magnetite (Fe3O4) and hematite (α-Fe2O3) have many important applications. Both forms of oxide can occur naturally during film growth by iron deposition under various oxidation environment; an important issue is to understand and control the process resulting in a single-phase film. We have performed in-situ real-time studies using x-ray diffraction of such film growth on sapphire (001) under pure ozone by monitoring the (00L) rod. Stable magnetite growth can be maintained at growth temperatures below 600° C up to a certain critical film thickness, beyond which the growth becomes hematite. The results demonstrate themore » importance of interfacial interaction in stabilizing the magnetite phase.« less
  • Thin films of CuCrO{sub 2} have been grown on Al{sub 2}O{sub 3}(001) substrates by oxygen plasma assisted molecular beam epitaxy. With a substrate temperature of 700 Degree-Sign C or 750 Degree-Sign C, the films showed an unanticipated (015) orientation but at a higher substrate temperature of 800 Degree-Sign C the expected basal (001) orientation predominates. The optical absorption spectrum of CuCrO{sub 2} shows a direct allowed absorption onset at 3.18 eV together with a weak peak at 2.0 eV which is suppressed by Sn doping. This suggests that the low energy peak should be attributed to 3d{yields}3d excitations associated withmore » Cu{sup 2+} defect states rather than excitations localised on Cr{sup 3+}. Valence band X-ray photoemission spectra of (001) and (015) oriented CuCrO{sub 2} are compared with those obtained from polycrystalline samples.« less
  • Epitaxial thin films of pure-phase Fe{sub 3}O{sub 4}(110), Fe{sub 3}O{sub 4}(111), {alpha}-Fe{sub 2}O{sub 3}(11{bar 2}0), and {alpha}-Fe{sub 2}O{sub 3}(1{bar 1}02) have been grown on MgO(110), {alpha}-Al{sub 2}O{sub 3}(0001), {alpha}-Al{sub 2}O{sub 3}(11{bar 2}0), and {alpha}-Al{sub 2}O{sub 3}(1{bar 1}02) substrates, respectively, by molecular beam epitaxy using an elemental Fe source and an electron cyclotron resonance oxygen plasma source. Characterization of the crystal structures, chemical states, and epitaxial relationships was carried out using a variety of techniques, including {ital in situ} reflection high-energy electron diffraction (RHEED), low-energy electron diffraction, x-ray photoelectron spectroscopy/diffraction, and {ital ex situ} x-ray reflectivity and diffraction. Real-time RHEED revealsmore » that Fe{sub 3}O{sub 4} growth on MgO appears in a step-flow fashion, whereas the growth of Fe{sub 3}O{sub 4}(111) on {alpha}-Al{sub 2}O{sub 3}(0001) occurs initially by island formation, and then island coalescence. However, the growth of {alpha}-Fe{sub 2}O{sub 3} on {alpha}-Al{sub 2}O{sub 3} appears to follow an intermediate growth mode. The formation of pure-phase films is controlled largely by oxygen partial pressure, plasma power, and growth rate, but appears to be independent of growth temperature, at least from 250 to 550{degree}C. The present study demonstrates that selective growth of pure-phase iron oxides with various low-index orientations can be achieved by controlling the growth conditions and selecting suitable substrates. {copyright} {ital 1997 American Vacuum Society.}« less
  • By systematically changing growth parameters, the growth of β-(Al{sub x}Ga{sub 1−x}){sub 2}O{sub 3}/Ga{sub 2}O{sub 3} (010) heterostructures by plasma-assisted molecular beam epitaxy was optimized. Through variation of the Al flux under O-rich conditions at 600 °C, β-(Al{sub x}Ga{sub 1−x}){sub 2}O{sub 3} (010) layers spanning ∼10% to ∼18% Al{sub 2}O{sub 3} were grown directly on β-Ga{sub 2}O{sub 3} (010) substrates. Nominal β-(Al{sub x}Ga{sub 1−x}){sub 2}O{sub 3} (010) compositions were determined through Al:Ga flux ratios. With x = ∼0.18, the β-(Al{sub x}Ga{sub 1−x}){sub 2}O{sub 3} (020) layer peak in a high-resolution x-ray diffraction (HRXRD) ω-2θ scan was barely discernible, and Pendellösung fringes were not visible.more » This indicated that the phase stability limit of Al{sub 2}O{sub 3} in β-Ga{sub 2}O{sub 3} (010) at 600 °C was less than ∼18%. The substrate temperature was then varied for a series of β-(Al{sub ∼0.15}Ga{sub ∼0.85}){sub 2}O{sub 3} (010) layers, and the smoothest layer was grown at 650 °C. The phase stability limit of Al{sub 2}O{sub 3} in β-Ga{sub 2}O{sub 3} (010) appeared to increase with growth temperature, as the β-(Al{sub x}Ga{sub 1−x}){sub 2}O{sub 3} (020) layer peak with x = ∼0.18 was easily distinguishable by HRXRD in a sample grown at 650 °C. Cross-sectional transmission electron microscopy (TEM) indicated that β-(Al{sub ∼0.15}Ga{sub ∼0.85}){sub 2}O{sub 3} (010) layers (14.4% Al{sub 2}O{sub 3} by energy dispersive x-ray spectroscopy) grown at 650 °C were homogeneous. β-(Al{sub ∼0.20}Ga{sub ∼0.80}){sub 2}O{sub 3} (010) layers, however, displayed a phase transition. TEM images of a β-(Al{sub ∼0.15}Ga{sub ∼0.85}){sub 2}O{sub 3}/Ga{sub 2}O{sub 3} (010) superlattice grown at 650 °C showed abrupt layer interfaces and high alloy homogeneity.« less
  • We report on the lattice relaxation mechanism of ZnO films grown on c-Al{sub 2}O{sub 3} substrates by plasma-assisted molecular-beam epitaxy. The lattice relaxation of ZnO films with various thicknesses up to 2000 nm is investigated by using both in situ time-resolved reflection high energy electron diffraction observation during the initial growth and absolute lattice constant measurements (Bond method) for grown films. The residual strain in the films is explained in terms of lattice misfit relaxation (compression) at the growth temperature and thermal stress (tension) due to the difference of growth and measurement temperatures. In thick films (>1 {mu}m), the residualmore » tensile strain begins to relax by bending and microcrack formation.« less