The characteristics of interface misfit dislocations for epitaxial α-Fe2O3 on α-Al2O3(0001)

Chong Min Wang, S. Thevuthasan, F. Gao, D. E. McCready, Scott A. Chambers

Research output: Contribution to journalArticle

24 Citations (Scopus)

Abstract

α-Fe2O3(0001) films of thickness equal to ∼7 nm and ∼70 nm were epitaxially grown on α-Al2O3(0001) by oxygen plasma-assisted molecular beam epitaxy. The interfaces were characterized using high resolution transmission electron microscopy, electron energy-loss spectroscopy, and X-ray diffraction. The interface exhibited coherent regions separated by equally-spaced misfit dislocations. When imaged from the [2̄110] direction, the dislocation spacing is 7.0 ± 1.1 nm for the 70-nm-thick specimen, and 7.2 ± 0.1 nm for the 7-nm-thick specimen. When imaged from the [011̄0] direction, the dislocation spacing is 4.5 ± 0.1 nm for the 7-nm-thick specimen. The experimentally observed dislocation spacings are approximately consistent with those calculated from the lattice mismatch between α-Al2O3 and α-Fe2O3, implying that the lattice mismatch is accommodated mainly by interface misfit dislocations above the critical thickness, which is less than 7 nm. This conclusion is also corroborated by the measured residual strain of ∼0.5% determined from X-ray diffraction for the 70 nm film. Electron-energy-loss-spectroscopy analysis reveals that the Fe L2,3-edge shows no measurable chemical shift relative to the L2,3-edge of structural Fe+3, indicating complete oxidation of Fe in the as-grown film.

Original languageEnglish
Pages (from-to)31-38
Number of pages8
JournalThin Solid Films
Volume414
Issue number1
DOIs
Publication statusPublished - 1 Jul 2002
Externally publishedYes

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Dislocations (crystals)
Lattice mismatch
Electron energy loss spectroscopy
spacing
X ray diffraction
Chemical shift
High resolution transmission electron microscopy
Molecular beam epitaxy
energy dissipation
electron energy
Oxygen
Plasmas
oxygen plasma
Oxidation
diffraction
spectroscopy
chemical equilibrium
x rays
molecular beam epitaxy
transmission electron microscopy

Keywords

  • Aluminium oxide
  • Interfaces
  • Iron oxide
  • Transmission electron microscopy

ASJC Scopus subject areas

  • Surfaces, Coatings and Films
  • Condensed Matter Physics
  • Surfaces and Interfaces

Cite this

The characteristics of interface misfit dislocations for epitaxial α-Fe2O3 on α-Al2O3(0001). / Wang, Chong Min; Thevuthasan, S.; Gao, F.; McCready, D. E.; Chambers, Scott A.

In: Thin Solid Films, Vol. 414, No. 1, 01.07.2002, p. 31-38.

Research output: Contribution to journalArticle

Wang, Chong Min ; Thevuthasan, S. ; Gao, F. ; McCready, D. E. ; Chambers, Scott A. / The characteristics of interface misfit dislocations for epitaxial α-Fe2O3 on α-Al2O3(0001). In: Thin Solid Films. 2002 ; Vol. 414, No. 1. pp. 31-38.
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AB - α-Fe2O3(0001) films of thickness equal to ∼7 nm and ∼70 nm were epitaxially grown on α-Al2O3(0001) by oxygen plasma-assisted molecular beam epitaxy. The interfaces were characterized using high resolution transmission electron microscopy, electron energy-loss spectroscopy, and X-ray diffraction. The interface exhibited coherent regions separated by equally-spaced misfit dislocations. When imaged from the [2̄110] direction, the dislocation spacing is 7.0 ± 1.1 nm for the 70-nm-thick specimen, and 7.2 ± 0.1 nm for the 7-nm-thick specimen. When imaged from the [011̄0] direction, the dislocation spacing is 4.5 ± 0.1 nm for the 7-nm-thick specimen. The experimentally observed dislocation spacings are approximately consistent with those calculated from the lattice mismatch between α-Al2O3 and α-Fe2O3, implying that the lattice mismatch is accommodated mainly by interface misfit dislocations above the critical thickness, which is less than 7 nm. This conclusion is also corroborated by the measured residual strain of ∼0.5% determined from X-ray diffraction for the 70 nm film. Electron-energy-loss-spectroscopy analysis reveals that the Fe L2,3-edge shows no measurable chemical shift relative to the L2,3-edge of structural Fe+3, indicating complete oxidation of Fe in the as-grown film.

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