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Magnuson, M., Tengdelius, L., Greczynski, G., Eriksson, F., Jensen, J., Lu, J., . . . Högberg, H. (2019). Compositional dependence of epitaxial Tin+1SiCn MAX-phase thin films grown from a Ti3SiC2 compound target. Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, 37(2), Article ID 021506.
Open this publication in new window or tab >>Compositional dependence of epitaxial Tin+1SiCn MAX-phase thin films grown from a Ti3SiC2 compound target
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2019 (English)In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 37, no 2, article id 021506Article in journal (Refereed) Published
Abstract [en]

The authors investigate sputtering of a Ti3SiC2 compound target at temperatures ranging from RT (no applied external heating) to 970 °C as well as the influence of the sputtering power at 850 °C for the deposition of Ti3SiC2 films on Al2O3(0001) substrates. Elemental composition obtained from time-of-flight energy elastic recoil detection analysis shows an excess of carbon in all films, which is explained by differences in the angular distribution between C, Si, and Ti, where C scatters the least during sputtering. The oxygen content is 2.6 at. % in the film deposited at RT and decreases with increasing deposition temperature, showing that higher temperatures favor high purity films. Chemical bonding analysis by x-ray photoelectron spectroscopy shows C–Ti and Si–C bonding in the Ti3SiC2 films and Si–Si bonding in the Ti3SiC2 compound target. X-ray diffraction reveals that the phases Ti3SiC2, Ti4SiC3, and Ti7Si2C5 can be deposited from a Ti3SiC2 compound target at substrate temperatures above 850 °C and with the growth of TiC and the Nowotny phase Ti5Si3Cx at lower temperatures. High-resolution scanning transmission electron microscopy shows epitaxial growth of Ti3SiC2, Ti4SiC3, and Ti7Si2C5 on TiC at 970 °C. Four-point probe resistivity measurements give values in the range ∼120 to ∼450 μΩ cm and with the lowest values obtained for films containing Ti3SiC2, Ti4SiC3, and Ti7Si2C5.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2019
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-154004 (URN)10.1116/1.5065468 (DOI)000460437200051 ()
Note

Funding agencies: Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU) [2009-00971]; Swedish Energy Research [43606-1]; Carl Tryggers Foundation [CTS16:303, CTS14:310, CTS 17:166]; Knut 

Available from: 2019-01-22 Created: 2019-01-22 Last updated: 2019-03-20Bibliographically approved
Magnuson, M., Greczynski, G., Eriksson, F., Hultman, L. & Högberg, H. (2019). Electronic Structure of ß-Ta Films from X-ray Photoelectron Spectroscopy and First-principles Calculations. Applied Surface Science, 470, 607-612
Open this publication in new window or tab >>Electronic Structure of ß-Ta Films from X-ray Photoelectron Spectroscopy and First-principles Calculations
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2019 (English)In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 470, p. 607-612Article in journal (Refereed) Published
Abstract [en]

The electronic structure and chemical bonding of ß-Ta synthesized as a thin 001-oriented film (space group P 21m) is investigated by 4f core level and valence band X-ray photoelectron spectroscopy and compared to α-Ta bulk. For the b-phase, the 4f7/2 peak is located at 21.91 eV and with the 4f5/2 at 23.81 eV which is 0.16 eV higher compared to the corresponding 4f peaks of the a-Ta reference. We suggest that this chemical shift originates from higher resistivity and tensile strain in the ß-Ta film. Furthermore, the 5d-5s states at the bottom of the valence band are shifted by 0.75 eV towards higher binding energy in ß-Ta compared to α-Ta. This is a consequence of the lower number of nearest neighbors with four in ß-Ta compared to eight in the α-Ta phase. The difference in the electronic structures, spectral line shapes of the valence band and the energy positions of the Ta 4f, 5p core-levels of b-Ta versus a-Ta are discussed in relation to calculated states of ß-Ta and α-Ta. In particular, the lower number of states at the Fermi level of ß-Ta (0.557 states/eV/atom) versus α-Ta (1.032 states/eV/atom) that according to Mott’s law should decrease the conductivity in metals and affect the stability by charge redistribution in the valence band. This is experimentally supported from resistivity measurements of the film yielding a value of ~170 µW cm in comparison to α-Ta bulk with a reported value of ~13.1 µW cm.

Keywords
β-Ta films, Valence band measurements, First-principles calculations, X-ray photoelectron spectroscopy, High power impulse magnetron sputtering
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-152876 (URN)10.1016/j.apsusc.2018.11.096 (DOI)000454997100069 ()
Note

Funding agencies: Swedish Government Strategic Research Area in Materials Science on Advanced Functional Materials at Linkoping University [2009-00971]; Swedish Energy Research [43606-1]; Carl Tryggers Foundation [CTS16:303, CTS14:310, CTS 17:166]; Knut and Alice Wallenber

Available from: 2018-11-26 Created: 2018-11-26 Last updated: 2019-01-21
Olovsson, W., Mizoguchi, T., Magnuson, M., Kontur, S., Hellman, O., Tanaka, I. & Draxl, C. (2019). Vibrational Effects in X-ray Absorption Spectra of Two-Dimensional Layered Materials. The Journal of Physical Chemistry C, 123(15), 9688-9692
Open this publication in new window or tab >>Vibrational Effects in X-ray Absorption Spectra of Two-Dimensional Layered Materials
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2019 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 123, no 15, p. 9688-9692Article in journal (Refereed) Published
Abstract [en]

With the examples of the C K-edge in graphite and the B K-edge in hexagonal boron nitride, we demonstrate the impact of vibrational coupling and lattice distortions on the X-ray absorption near-edge structure (XANES) in two-dimensional layered materials. Theoretical XANES spectra are obtained by solving the Bethe–Salpeter equation of many-body perturbation theory, including excitonic effects through the correlated motion of the core hole and excited electron. We show that accounting for zero-point motion is important for the interpretation and understanding of the measured X-ray absorption fine structure in both materials, in particular for describing the σ*-peak structure.

Place, publisher, year, edition, pages
ACS Publications, 2019
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-156490 (URN)10.1021/acs.jpcc.9b00179 (DOI)000465488600005 ()
Note

Funding agencies:  Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [2009 00971]; Knut and Alice Wallenbergs Foundation; Swedish Energy Research [43606-1]; Carl Trygger Foundation [CTS16:303, CTS14:310]; JSPS KA

Available from: 2019-04-24 Created: 2019-04-24 Last updated: 2019-07-01Bibliographically approved
Magnuson, M., Halim, J. & Näslund, L.-Å. (2018). Chemical bonding in carbide MXene nanosheets. Journal of Electron Spectroscopy and Related Phenomena, 224, 27-32
Open this publication in new window or tab >>Chemical bonding in carbide MXene nanosheets
2018 (English)In: Journal of Electron Spectroscopy and Related Phenomena, ISSN 0368-2048, E-ISSN 1873-2526, Vol. 224, p. 27-32Article in journal (Refereed) Published
Abstract [en]

tThe chemical bonding in the carbide core and the surface chemistry in a new group of transition-metalcarbides Tin+1Cn-Tx(n = 1,2) called MXenes have been investigated by surface-sensitive valence bandX-ray photoelectron spectroscopy. Changes in band structures of stacked nano sheets of different thick-nesses are analyzed in connection to known hybridization regions of TiC and TiO2that affect elastic andtransport properties. By employing high excitation energy, the photoelectron cross-section for the C 2s– Ti 3d hybridization region at the bottom of the valence band is enhanced. As shown in this work, theO 2p and F 2p bands strongly depend both on the bond lengths to the surface groups and the adsorptionsites. The effect of surface oxidation and Ar+sputtering on the electronic structure is also discussed.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
MXene, 2D materials, Valence band, X-ray photoelecton spectroscopy, XPS, Chemical bonding, Termination species
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-145690 (URN)10.1016/j.elspec.2017.09.006 (DOI)000428825400006 ()2-s2.0-85030792688 (Scopus ID)
Available from: 2018-03-16 Created: 2018-03-16 Last updated: 2019-06-28Bibliographically approved
Magnuson, M., Tengdelius, L., Greczynski, G., Hultman, L. & Högberg, H. (2018). ­Chemical Bonding in Epitaxial ZrB2 Studied by X-ray Spectroscopy. Thin Solid Films, 649, 89-96
Open this publication in new window or tab >>­Chemical Bonding in Epitaxial ZrB2 Studied by X-ray Spectroscopy
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2018 (English)In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 649, p. 89-96Article in journal (Refereed) Published
Abstract [en]

The chemical bonding in an epitaxial ZrB2 film is investigated by Zr K-edge (1s) X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopies and compared to the ZrB2 compound target from which the film was synthesized as well as a bulk α-Zr reference. Quantitative analysis of X-ray Photoelectron Spectroscopy spectra reveals at the surface: ~5% O in the epitaxial ZrB2 film, ~19% O in the ZrB2 compound target and ~22% O in the bulk α-Zr reference after completed sputter cleaning. For the ZrB2 compound target, X-ray diffraction (XRD) shows weak but visible   11, 111, and 220 peaks from monoclinic ZrO2 together with peaks from ZrB2 and where the intensity distribution for the ZrB2 peaks show a randomly oriented target material.  For the bulk α-Zr reference no peaks from any crystalline oxide were visible in the diffractogram recorded from the 0001-oriented metal. The Zr K-edge absorption from the two ZrB2 samples demonstrate more pronounced oscillations for the epitaxial ZrB2 film than in the bulk ZrB2 attributed to the high atomic ordering within the columns of the film. The XANES exhibits no pre-peak due to lack of p-d hybridization in ZrB2, but with a chemical shift towards higher energy of 4 eV in the film and 6 eV for the bulk compared to α-Zr (17.993 keV) from the charge-transfer from Zr to B. The 2 eV larger shift in bulk ZrB2 material suggests higher oxygen content than in the epitaxial film, which is supported by XPS. In EXAFS, the modelled cell-edge in ZrB2 is slightly smaller in the thin film (a=3.165 Å, c=3.520 Å) in comparison to the bulk target material (a=3.175 Å, c=3.540 Å) while in hexagonal closest-packed metal (α-phase, a=3.254 Å, c=5.147 Å). The modelled coordination numbers show that the EXAFS spectra of the epitaxial ZrB2 film is highly anisotropic with strong in-plane contribution, while the bulk target material is more isotropic. The Zr-B distance in the film of 2.539 Å is in agreement with the calculated value from XRD data of 2.542 Å. This is slightly shorter compared to that in the ZrB2 compound target 2.599 Å, supporting the XANES results of a higher atomic order within the columns of the film compared to bulk ZrB2.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
Zirconium boride, thin films, bond distances, chemical bonding, X-ray spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-144578 (URN)10.1016/j.tsf.2018.01.021 (DOI)000427524100015 ()
Note

Funding agencies: Swedish Energy Research [43606-1]; Swedish Foundation for Strategic Research (SSF) through the synergy grant FUNCASE [RMA11-0029]; Carl Trygger Foundation [CTS16:303, CTS14:310]; Swedish Research Council (VR) [621-2010 3921]; Knut and Alice Wallenberg Fou

Available from: 2018-01-29 Created: 2018-01-29 Last updated: 2018-11-29Bibliographically approved
Magnuson, M., Schmitt, T. & Duda, L. (2018). Polarization-dependent resonant inelastic X-ray scattering study atthe Cu L and O K-edges of YBa2Cu3O7-x. Journal of Electron Spectroscopy and Related Phenomena, 224, 38-44
Open this publication in new window or tab >>Polarization-dependent resonant inelastic X-ray scattering study atthe Cu L and O K-edges of YBa2Cu3O7-x
2018 (English)In: Journal of Electron Spectroscopy and Related Phenomena, ISSN 0368-2048, E-ISSN 1873-2526, Vol. 224, p. 38-44Article in journal (Refereed) Published
Abstract [en]

We present a study on the high-Tc superconductor (HTSC) YBa2Cu3O7-x(YBCO) using polarization-dependent X-ray absorption and resonant inelastic X-ray scattering. High-resolution measurementsusing synchrotron-radiation are compared with calculations using a quasi-atomic multiplet approachperformed at the Cu 2p3/2-edge of YBCO. We use a multiplet approach within the single impurity Ander-son model to reproduce and understand the character of the localized low-energy excitations in YBCO.We observe a distinct peak at about 0.5 eV in O K RIXS. This peak shows dependence on doping, incidentenergy, and momentum transfer that suggests that it has a different origin than the previously discussedcuprate bimagnons. Therefore, we assign it to bimagnon excitations within the Zhang Rice bands and/orthe Upper Hubbard bands, respectively.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
H-Tc superconductors, YBCO, cuprates, RIXS
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-145691 (URN)10.1016/j.elspec.2017.07.005 (DOI)000428825400008 ()2-s2.0-85029521510 (Scopus ID)
Available from: 2018-03-16 Created: 2018-03-16 Last updated: 2018-11-29Bibliographically approved
Magnuson, M., Eriksson, F., Hultman, L. & Högberg, H. (2017). Bonding Structures of ZrHx Thin Films by X-ray Spectroscopy. The Journal of Physical Chemistry C, 121, 25750-25758
Open this publication in new window or tab >>Bonding Structures of ZrHx Thin Films by X-ray Spectroscopy
2017 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 121, p. 25750-25758Article in journal (Refereed) Published
Abstract [en]

The variation in local atomic structure and chemical bonding of ZrHx (x=0.15, 0.30, 1.16) magnetron sputtered thin films are investigated by Zr K-edge (1s) X-ray absorption near-edge structure and extended X-ray absorption fine structure spectroscopies. A chemical shift of the Zr K-edge towards higher energy with increasing hydrogen content is observed due to charge-transfer and an ionic or polar covalent bonding component between the Zr 4d and the H 1s states with increasing valency for Zr. We find an increase in the Zr-Zr bond distance with increasing hydrogen content from 3.160 Å in the hexagonal closest-packed metal (a-phase) to 3.395 Å in the understoichiometric d-ZrHx film (CaF2-type structure) with x=1.16 that largely resembles that of bulk d-ZrH2. For yet lower hydrogen contents, the structures are mixed a- and d-phases, while sufficient hydrogen loading (x>1) yields a pure δ-phase that is understoichiometric, but thermodynamically stable. The change in the hydrogen content and strain is discussed in relation to the corresponding change of bond lengths, hybridizations, and trends in electrical resistivity.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2017
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-143207 (URN)10.1021/acs.jpcc.7b03223 (DOI)000416496200016 ()
Funder
Swedish Energy Agency, 43606-1Swedish Foundation for Strategic Research , FUNCASE [RMA11-0029]Carl Tryggers foundation , CTS16:303, CTS14:310
Note

Funding agencies: Swedish Government Strategic Research Area in Materials Science on Functiona

Available from: 2017-11-23 Created: 2017-11-23 Last updated: 2018-06-04
Olovsson, W., Alling, B. & Magnuson, M. (2016). Structure and Bonding in Amorphous Cr1−xCx Nanocomposite Thin Films: X‐ray Absorption Spectra and First-Principles Calculations. The Journal of Physical Chemistry C, 120(23), 12890-12899
Open this publication in new window or tab >>Structure and Bonding in Amorphous Cr1−xCx Nanocomposite Thin Films: X‐ray Absorption Spectra and First-Principles Calculations
2016 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 120, no 23, p. 12890-12899Article in journal (Refereed) Published
Abstract [en]

The local structure and chemical bonding in two-phase amorphous Cr1−xCx nanocomposite thin films are investigated by Cr K-edge (1s) X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopies in comparison to theory. By utilizing the computationally efficient stochastic quenching (SQ) technique, we reveal the complexity of different Cr-sites in the transition metal carbides, highlighting the need for large scale averaging to obtain theoretical XANES and EXAFS spectra for comparison with measurements. As shown in this work, it is advantageous to use ab initio theory as an assessment to correctly model and fit experimental spectra and investigate the trends of bond lengths and coordination numbers in complex amorphous materials. With sufficient total carbon content (≥30 at. %), we find that the short-range coordination in the amorphous carbide phase exhibit similarities to that of a Cr7C3 ± y structure, while excessive carbons assemble in the amorphous carbon phase.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2016
National Category
Inorganic Chemistry Theoretical Chemistry Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-129386 (URN)10.1021/acs.jpcc.6b03608 (DOI)000378196200059 ()
Note

Funding agencies:We would like to thank the staff at MAX-lab for experimental support and U. Jansson and M. Andersson for providing the samples. This work was supported by the Swedish Research Council (VR) Linnaeus Grant LiLi-NFM, the FUNCASE project supported Swedish Strategic Research Foundation (SSF). W.O. acknowledges financial support from VR Grant No. 621-2011-4426, the Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU No 2009 00971), Knut and Alice Wallenbergs Foundation project Strong Field Physics and New States of Matter 2014-2019 (COTXS). B.A. would like to thank E. Holmstrom and R. Lizarraga for support with the SQ method and acknowledges financial support by the Swedish Research Council (VR) through the young researcher Grant No. 621-2011-4417 and the international career Grant No. 330-2014-6336 and Marie Sklodowska Curie Actions, Cofund, Project INCA 600398. The calculations were performed using supercomputer resources provided by the Swedish National Infrastructure for Computing (SNIC) at the National Supercomputer Centre (NSC) and Center for Parallel Computing (PDC).

Available from: 2016-06-17 Created: 2016-06-17 Last updated: 2018-06-04Bibliographically approved
Furlan, A., Jansson, U., Lu, J., Hultman, L. & Magnuson, M. (2015). Structure and bonding in amorphous iron carbide thin films. Journal of Physics: Condensed Matter, 27(4), 045002
Open this publication in new window or tab >>Structure and bonding in amorphous iron carbide thin films
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2015 (English)In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 27, no 4, p. 045002-Article in journal (Refereed) Published
Abstract [en]

We investigate the amorphous structure, chemical bonding, and electrical properties ofmagnetron sputtered Fe1−xCx (0.21 < x < 0.72) thin films. X-ray, electron diffraction andtransmission electron microscopy show that the Fe1−xCx films are amorphousnanocomposites, consisting of a two-phase domain structure with Fe-rich carbidic FeCy , and acarbon-rich matrix. Pair distribution function analysis indicates a close-range order similar tothose of crystalline Fe3C carbides in all films with additional graphene-like structures at highcarbon content (71.8 at% C). From x-ray photoelectron spectroscopy measurements, we findthat the amorphous carbidic phase has a composition of 15–25 at% carbon that slightlyincreases with total carbon content. X-ray absorption spectra exhibit an increasing number ofunoccupied 3d states and a decreasing number of C 2p states as a function of carbon content.These changes signify a systematic redistribution in orbital occupation due to charge-transfereffects at the domain-size-dependent carbide/matrix interfaces. The four-point proberesistivity of the Fe1−xCx films increases exponentially with carbon content from ∼200μcm(x = 0.21) to ∼1200μcm (x = 0.72), and is found to depend on the total carbon contentrather than the composition of the carbide. Our findings open new possibilities for modifyingthe resistivity of amorphous thin film coatings based on transition metal carbides through thecontrol of amorphous domain structures.

Place, publisher, year, edition, pages
Institute of Physics Publishing (IOPP), 2015
Keywords
iron carbide, thin film coatings, sputtering, synchrotron radiation, amorphous nanocomposites, TEM, RDF
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-113089 (URN)10.1088/0953-8984/27/4/045002 (DOI)000348493500002 ()25567721 (PubMedID)
Note

We would like to thank the staff at the MAX IV Laboratory for experimental support, and Jill Sundberg, UU, for help with the Raman measurements. The work was supported by the Swedish Research Council (VR) by project, and Linnaeus grants (VR 2008-6582). MM, UJ and JL also acknowledge the Swedish Foundation for Strategic Research Synergy Project FUNCASE (RMA11-0029).

Available from: 2015-01-08 Created: 2015-01-08 Last updated: 2018-06-04
Magnuson, M., Mattesini, M., Bugnet, M. & Eklund, P. (2015). The origin of anisotropy and high density of states in the electronic structure of Cr2GeC by means of polarized soft X-ray spectroscopy and ab initio calculations. Journal of Physics: Condensed Matter, 27(41), 415501-415509
Open this publication in new window or tab >>The origin of anisotropy and high density of states in the electronic structure of Cr2GeC by means of polarized soft X-ray spectroscopy and ab initio calculations
2015 (English)In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 27, no 41, p. 415501-415509Article in journal (Refereed) Published
Abstract [en]

The anisotropy in the electronic structure of the inherently nanolaminated ternary phase Cr2GeC is investigated by bulk-sensitive and element selective soft x-ray absorption/emission spectroscopy. The angle-resolved absorption/emission measurements reveal di erences between the in-plane and out-of-plane bonding at the (0001) interfaces of Cr2GeC. The Cr L2;3, C K, and Ge M1, M2;3 emission spectra are interpreted with rst-principles density-functional theory (DFT) including core-tovalence dipole transition matrix elements. For the Ge 4s states, the x-ray emission measurements reveal two orders of magnitude higher intensity at the Fermi level than DFT within the General Gradient Approximation (GGA) predicts. We provide direct evidence of anisotropy in the electronic structure and the orbital occupation that should a ect the thermal expansion coecient and transport properties. As shown in this work, hybridization and redistribution of intensity from the shallow 3d core levels to the 4s valence band explain the large Ge density of states at the Fermi level.

Place, publisher, year, edition, pages
Bristol, UK: Institute of Physics Publishing Ltd., 2015
Keywords
MAX-phases, spectroscopy, DFT, electronic structure
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-121642 (URN)10.1088/0953-8984/27/41/415501 (DOI)000362572100008 ()26414914 (PubMedID)
Available from: 2015-09-29 Created: 2015-09-29 Last updated: 2018-06-04Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0002-0317-0190

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