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Ultrahigh vacuum dc magnetron sputter-deposition of epitaxial Pd(111)/Al2O3(0001) thin films

Aleman, Angel; Li, Chao; Zaid, Hicham; Kindlund, Hanna LU ; Fankhauser, Joshua; Prikhodko, Sergey V.; Goorsky, Mark S. and Kodambaka, Suneel LU (2018) In Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films 36(3).
Abstract

Pd(111) thin films, ∼245 nm thick, are deposited on Al2O3(0001) substrates at ≈0.5Tm, where Tm is the Pd melting point, by ultrahigh vacuum dc magnetron sputtering of Pd target in pure Ar discharges. Auger electron spectra and low-energy electron diffraction patterns acquired in situ from the as-deposited samples reveal that the surfaces are compositionally pure 111-oriented Pd. Double-axis x-ray diffraction (XRD) ω-2θ scans show only the set of Pd 111 peaks from the film. In triple-axis high-resolution XRD, the full width at half maximum intensity Γω of the Pd 111 ω-rocking curve is 630 arc sec. XRD 111 pole figure obtained from the sample revealed six peaks 60°-apart at a tilt... (More)

Pd(111) thin films, ∼245 nm thick, are deposited on Al2O3(0001) substrates at ≈0.5Tm, where Tm is the Pd melting point, by ultrahigh vacuum dc magnetron sputtering of Pd target in pure Ar discharges. Auger electron spectra and low-energy electron diffraction patterns acquired in situ from the as-deposited samples reveal that the surfaces are compositionally pure 111-oriented Pd. Double-axis x-ray diffraction (XRD) ω-2θ scans show only the set of Pd 111 peaks from the film. In triple-axis high-resolution XRD, the full width at half maximum intensity Γω of the Pd 111 ω-rocking curve is 630 arc sec. XRD 111 pole figure obtained from the sample revealed six peaks 60°-apart at a tilt angles corresponding to Pd 111 reflections. XRD φ scans show six 60°-rotated 111 peaks of Pd at the same φ angles for 11 23 of Al2O3 based on which the epitaxial crystallographic relationships between the film and the substrate are determined as (111)Pd∥ (0001)Al2O3 with two in-plane orientations of [112]Pd∥ [1120]Al2O3 and [211]Pd∥ [1120]Al2O3. Using triple axis symmetric and asymmetric reciprocal space maps, interplanar spacings of out-of-plane (111) and in-plane (11 2) are found to be 0.2242 ± 0.0003 and 0.1591 ± 0.0003 nm, respectively. These values are 0.18% lower than 0.2246 nm for (111) and the same, within the measurement uncertainties, as 0.1588 nm for (11 2) calculated from the bulk Pd lattice parameter, suggesting a small out-of-plane compressive strain and an in-plane tensile strain related to the thermal strain upon cooling the sample from the deposition temperature to room temperature. High-resolution cross-sectional transmission electron microscopy coupled with energy dispersive x-ray spectra obtained from the Pd(111)/Al2O3(0001) samples indicate that the Pd-Al2O3 interfaces are essentially atomically abrupt and dislocation-free. These results demonstrate the growth of epitaxial Pd thin films with (111) out-of-plane orientation with low mosaicity on Al2O3(0001).

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publication status
published
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in
Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films
volume
36
issue
3
publisher
American Vacuum Society
external identifiers
  • scopus:85044418311
ISSN
0734-2101
DOI
10.1116/1.5021609
language
English
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yes
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9fd58d41-012a-4412-b417-1f30bd6878cf
date added to LUP
2018-05-03 08:44:33
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2019-08-14 04:15:44
@article{9fd58d41-012a-4412-b417-1f30bd6878cf,
  abstract     = {<p>Pd(111) thin films, ∼245 nm thick, are deposited on Al<sub>2</sub>O<sub>3</sub>(0001) substrates at ≈0.5T<sub>m</sub>, where T<sub>m</sub> is the Pd melting point, by ultrahigh vacuum dc magnetron sputtering of Pd target in pure Ar discharges. Auger electron spectra and low-energy electron diffraction patterns acquired in situ from the as-deposited samples reveal that the surfaces are compositionally pure 111-oriented Pd. Double-axis x-ray diffraction (XRD) ω-2θ scans show only the set of Pd 111 peaks from the film. In triple-axis high-resolution XRD, the full width at half maximum intensity Γ<sub>ω</sub> of the Pd 111 ω-rocking curve is 630 arc sec. XRD 111 pole figure obtained from the sample revealed six peaks 60°-apart at a tilt angles corresponding to Pd 111 reflections. XRD φ scans show six 60°-rotated 111 peaks of Pd at the same φ angles for 11 23 of Al<sub>2</sub>O<sub>3</sub> based on which the epitaxial crystallographic relationships between the film and the substrate are determined as (111)Pd∥ (0001)Al2O3 with two in-plane orientations of [112]Pd∥ [1120]Al2O3 and [211]Pd∥ [1120]Al2O3. Using triple axis symmetric and asymmetric reciprocal space maps, interplanar spacings of out-of-plane (111) and in-plane (11 2) are found to be 0.2242 ± 0.0003 and 0.1591 ± 0.0003 nm, respectively. These values are 0.18% lower than 0.2246 nm for (111) and the same, within the measurement uncertainties, as 0.1588 nm for (11 2) calculated from the bulk Pd lattice parameter, suggesting a small out-of-plane compressive strain and an in-plane tensile strain related to the thermal strain upon cooling the sample from the deposition temperature to room temperature. High-resolution cross-sectional transmission electron microscopy coupled with energy dispersive x-ray spectra obtained from the Pd(111)/Al<sub>2</sub>O<sub>3</sub>(0001) samples indicate that the Pd-Al<sub>2</sub>O<sub>3</sub> interfaces are essentially atomically abrupt and dislocation-free. These results demonstrate the growth of epitaxial Pd thin films with (111) out-of-plane orientation with low mosaicity on Al<sub>2</sub>O<sub>3</sub>(0001).</p>},
  articleno    = {030602},
  author       = {Aleman, Angel and Li, Chao and Zaid, Hicham and Kindlund, Hanna and Fankhauser, Joshua and Prikhodko, Sergey V. and Goorsky, Mark S. and Kodambaka, Suneel},
  issn         = {0734-2101},
  language     = {eng},
  month        = {05},
  number       = {3},
  publisher    = {American Vacuum Society},
  series       = {Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films},
  title        = {Ultrahigh vacuum dc magnetron sputter-deposition of epitaxial Pd(111)/Al<sub>2</sub>O<sub>3</sub>(0001) thin films},
  url          = {http://dx.doi.org/10.1116/1.5021609},
  volume       = {36},
  year         = {2018},
}