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Green, Sara
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Publications (10 of 31) Show all publications
Malmgren, S., Green, S. & Niklasson, G. A. (2017). Anomalous diffusion of ions in electrochromic tungsten oxide films. Electrochimica Acta, 247, 252-257
Open this publication in new window or tab >>Anomalous diffusion of ions in electrochromic tungsten oxide films
2017 (English)In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 247, p. 252-257Article in journal (Refereed) Published
Abstract [en]

Amorphous tungsten oxide thinfilms were deposited by sputtering at different O2/Ar ratios onto conducting substrates. Ion intercalation and diffusion in thefilms was studied by electrochemical impedance spectroscopy measurements in the frequency range 10 mHz–100 kHz and for potentials between 1.0 and 3.2 V vs. Li/Li+, using the film as working electrode in a Li+ containing electrolyte. The impedance data were in very good agreement with anomalous diffusion models. Different models were found to be applicable at potentials >1.8 V and <1.8 V. At high potentials ion intercalation was found to be reversible and an anomalous diffusion model describing ion hopping was favored. At low potentials ion intercalation was found to be irreversible and ion trapping takes place. In this latter range an anomalous diffusion model for the case of non-conserved number of charge carriers gave the best fit to experimentaldata. We obtained potential dependent diffusion coefficients in the range from 109 to 1011cm2/s, and anomalous diffusion exponents in the range 0.1 to 0.4, with the films deposited at lower O2/Ar ratios exhibiting the higher values.

Place, publisher, year, edition, pages
Elsevier, 2017
Keywords
Electrochromism impedance spectroscopy anomalous diffusion tungsten oxide
National Category
Materials Engineering
Research subject
Engineering Science with specialization in Solid State Physics
Identifiers
urn:nbn:se:uu:diva-332918 (URN)10.1016/j.electacta.2017.06.079 (DOI)000408582300027 ()
Funder
Swedish Research Council, 2016-03713
Available from: 2017-11-02 Created: 2017-11-02 Last updated: 2019-02-01Bibliographically approved
Green, S., Granqvist, C.-G. & Niklasson, G. (2014). Structure and optical properties of electrochromic tungsten-containing nickel oxide films. Paper presented at 10th International Meeting on Electrochromism (IME), Holland, MI, August 12-16, 2012. Solar Energy Materials and Solar Cells, 126, 248-259
Open this publication in new window or tab >>Structure and optical properties of electrochromic tungsten-containing nickel oxide films
2014 (English)In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 126, p. 248-259Article in journal (Refereed) Published
Abstract [en]

Electrochromic NixW1-x oxide thin films with 0.5 < x < 1, were deposited by co-sputtering from one Ni and one W metal target. The different compositions were structurally characterized by X-ray diffraction, X-ray photoelectron spectroscopy and Rutherford backscattering spectroscopy. The optical and electrochemical properties were investigated by spectrophotometry and cyclic voltammetry in LiClO4 dissolved in propylene carbonate. It was found that the samples turned amorphous upon W addition and that the NixW1-x oxides probably consisted of hydrated Ni oxides and NiWO4. The charge insertion/extraction and optical modulation was unfortunately very modest. Moreover, an aging effect, resulting in a strong bleaching process of the samples was observed. Nevertheless, it was found that, for electrochromic applications, the advantage of W addition was that the transparency at the bleached state was enhanced for all compositions and for wavelengths of 400 nm up to NIR.

National Category
Materials Engineering
Research subject
Engineering Science with specialization in Solid State Physics
Identifiers
urn:nbn:se:uu:diva-179763 (URN)10.1016/j.solmat.2013.04.001 (DOI)000338395100036 ()
Conference
10th International Meeting on Electrochromism (IME), Holland, MI, August 12-16, 2012
Available from: 2012-08-22 Created: 2012-08-22 Last updated: 2017-12-07Bibliographically approved
Green, S. (2012). Electrochromic Nickel – Tungsten Oxides: Optical, Electrochemical and Structural Characterization of Sputter-deposited Thin Films in the Whole Composition Range. (Doctoral dissertation). Uppsala: Acta Universitatis Upsaliensis
Open this publication in new window or tab >>Electrochromic Nickel – Tungsten Oxides: Optical, Electrochemical and Structural Characterization of Sputter-deposited Thin Films in the Whole Composition Range
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis investigates the electrochromic NixW1-x oxide thin film system, where 0 < x < 1. The thin films were deposited by reactive DC magnetron co-sputtering from one Ni and one W metal target. In addition, Ni oxide was deposited with water vapor added to the sputtering gas. The different compositions were structurally characterized by X-ray diffraction, X-ray photoelectron-, Rutherford backscattering- and Raman spectroscopy. Possible nanostructures were studied by ellipsometry together with effective medium theory. Optical and electrochemical properties were investigated by spectrophotometry and cyclic voltammetry in 1 M lithium perchlorate in propylene carbonate (Li-PC). Li-PC electrolyte was used as it is being compatible with both W and Ni oxides. Few studies have previously been made on Ni oxides in Li-PC.

Films with high Ni content, 0.85 < x < 1, were polycrystalline and all other films were amorphous. W-rich films, x < 0.5, consisted of a mixture of W oxide and NiWO4 -phases, and the Ni-rich samples, x > 0.5, probably consisted of hydrated Ni oxide and NiWO4 -phases. Films with 0 < x < 0.3 showed electrochromic properties similar to W oxide, and films with 0.7 < x < 1 behaved as Ni oxide. For 0.4 < x < 0.7 no optical change was seen. At the border of cathodic electrochromic and non-electrochromic behavior, i.e. x ~ 0.4, the sample behaved as an optically passive intercalation material. The transmittance change was 0.45 and 0.15 for the W-rich and Ni-rich films, respectively. Ni addition to W oxide improved the coloration efficiency. For the Ni-rich films the charge insertion/extraction and optical modulation was low and an aging effect resulted in strong bleaching of the samples. The advantage of W addition to Ni oxide was that the transparency at the bleached state was enhanced. Moreover, it was found that the hydrous character of the Ni oxide had a large impact on the electrochromic performance, both when electrochemically cycled in KOH and in the non-aqueous Li-PC.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2012. p. 116
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 963
Keywords
Electrochromism, Nickel oxide, Tungsten oxide, Lithium intercalation, Sputtering, Thin films, Nanostructures, Optical properties
National Category
Materials Engineering
Research subject
Solid State Physics
Identifiers
urn:nbn:se:uu:diva-179764 (URN)978-91-554-8444-6 (ISBN)
Public defence
2012-10-12, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:15 (English)
Opponent
Supervisors
Available from: 2012-09-21 Created: 2012-08-22 Last updated: 2013-01-22Bibliographically approved
Green, S. V., Watanabe, M., Oka, N., Niklasson, G. A., Granqvist, C.-G. & Shigesato, Y. (2012). Electrochromic properties of nickel oxide based thin films sputter deposited in the presence of water vapor. Thin Solid Films, 520(10), 3839-3842
Open this publication in new window or tab >>Electrochromic properties of nickel oxide based thin films sputter deposited in the presence of water vapor
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2012 (English)In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 520, no 10, p. 3839-3842Article in journal (Refereed) Published
Abstract [en]

Electrochromic nickel oxide based thin films were prepared by reactive RF magnetron sputtering from metallic nickel in the presence of Ar, O-2 and H2O. The water vapor led to enhanced optical modulation and charge capacity. At a wavelength of 550 nm the bleached state transmittance was 0.73 and the transmittance for the colored state was 0.28 and 0.15 for water partial pressures of p(H2O)<10(-3) Pa and p(H2O) similar to 7 x 10(-2) Pa, respectively. The charge densities were 14 and 25 mC/cm(2) for p(H2O)<10(-3) Pa and P-H2O similar to 7 x 10(-2) Pa, respectively. The coloration efficiency was decreased with increased water partial pressure, from about 0.07 to 0.06 cm(2)/mC. Preliminary results show that the H2O promotes an amorphous structure and makes the films increasingly hydrous. 

Keywords
Nickel oxide, Electrochromism, RF magnetron sputtering, Water vapor, Thin film, Optical properties, Charge capacity
National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Solid State Physics
Identifiers
urn:nbn:se:uu:diva-174595 (URN)10.1016/j.tsf.2011.08.030 (DOI)000302973400027 ()
Available from: 2012-05-24 Created: 2012-05-22 Last updated: 2017-12-07Bibliographically approved
Green, S., Granqvist, C.-G. & Niklasson, G. A. (2012). Electrochromism in Nickel-Tungsten Oxides.. In: IME-10. Tenth International meeting on Electrochromism, Holland, MI USA, August 12-16, 2012.. Paper presented at IME-10. Tenth International meeting on Electrochromism, Holland, MI USA, August 12-16, 2012. (pp. 17).
Open this publication in new window or tab >>Electrochromism in Nickel-Tungsten Oxides.
2012 (English)In: IME-10. Tenth International meeting on Electrochromism, Holland, MI USA, August 12-16, 2012., 2012, p. 17-Conference paper, Oral presentation with published abstract (Refereed)
National Category
Condensed Matter Physics Engineering and Technology
Research subject
Engineering Science with specialization in Solid State Physics
Identifiers
urn:nbn:se:uu:diva-187680 (URN)
Conference
IME-10. Tenth International meeting on Electrochromism, Holland, MI USA, August 12-16, 2012.
Available from: 2012-12-10 Created: 2012-12-10 Last updated: 2015-06-24
Green, S. V., Pehlivan, E., Granqvist, C.-G. & Niklasson, G. A. (2012). Electrochromism in sputter deposited nickel-containing tungsten oxide films. Solar Energy Materials and Solar Cells, 99, 339-344
Open this publication in new window or tab >>Electrochromism in sputter deposited nickel-containing tungsten oxide films
2012 (English)In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 99, p. 339-344Article in journal (Refereed) Published
Abstract [en]

Thin films of NixW1-x oxide were prepared by reactive DC magnetron co-sputtering and were investigated by optical and electrochemical measurements. Electrochromism was found only for 0<x<0.3 but not for 0.3<x<0.6, though films with x~0.4 could still sustain reversible charge insertion. The coloration efficiency was largest for 0.10<x<0.15. The charge capacity of the NixW1-x oxide films decreased upon increasing the value of x as a consequence of a decreasing ion diffusion coefficient leading to slower kinetics.

National Category
Materials Engineering
Research subject
Engineering Science with specialization in Solid State Physics
Identifiers
urn:nbn:se:uu:diva-178580 (URN)10.1016/j.solmat.2011.12.025 (DOI)000301167200048 ()
Funder
Swedish Research CouncilEU, FP7, Seventh Framework Programme, 211948Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning
Available from: 2012-07-31 Created: 2012-07-31 Last updated: 2017-12-07Bibliographically approved
Valyukh, I., Green, S., Granqvist, C.-G., Gunnarsson, K., Arwin, H. & Niklasson, G. A. (2012). Ellipsometrically determined optical properties of nickel-containing tungsten oxide thin films: Nanostructure inferred from effective medium theory. Journal of Applied Physics, 112(4), 044308
Open this publication in new window or tab >>Ellipsometrically determined optical properties of nickel-containing tungsten oxide thin films: Nanostructure inferred from effective medium theory
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2012 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 112, no 4, p. 044308-Article in journal (Refereed) Published
Abstract [en]

Films of NixW1−x oxide with 0.05 ≤ x ≤ 0.53 were produced by reactive dc magnetron co-sputtering onto Si. Such films have documented electrochromism. Spectroscopic ellipsometry was used to extract accurate data on the dielectric function in the photon range 0.062 to 5.62 eV. The results for 0.62 to 5.62 eV were compared with computations from the Bruggeman effective medium theory applied to two nanostructural models: one representing a random mixture of structural entities characterized by the dielectric functions of WO3 and NiWO4 and the other describing a random mixture of WO3 and NiO. Unambiguous evidence was found in favor of the former model, and hence the films are composed of nanosized tungsten oxide and nickel tungstate. This agrees excellently with an earlier investigation of ours on NixW1−x oxide films, where nanostructure was inferred from Raman spectroscopy, x-ray photoelectron spectroscopy, and x-ray diffraction.

National Category
Materials Engineering
Research subject
Engineering Science with specialization in Solid State Physics
Identifiers
urn:nbn:se:uu:diva-179762 (URN)10.1063/1.4748166 (DOI)000308410100079 ()
Available from: 2012-08-22 Created: 2012-08-22 Last updated: 2017-12-07Bibliographically approved
Valyukh, I., Green, S., Granqvist, C.-G., Niklasson, G. A., Valyukh, S. & Arwin, H. (2011). Optical properties of thin films of mixed Ni-W oxide made by reactive DC magnetron sputtering. Thin Solid Films, 519(9), 2914-2918
Open this publication in new window or tab >>Optical properties of thin films of mixed Ni-W oxide made by reactive DC magnetron sputtering
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2011 (English)In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 519, no 9, p. 2914-2918Article in journal (Refereed) Published
Abstract [en]

Thin films of NixW1-x oxides with x = 0.05, 0.19, 0.43 and 0.90 were studied. Films with thicknesses in the range 125-250 nm were deposited on silicon wafers at room temperature by reactive DC magnetron co-sputtering from targets of Ni and W. The films were characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM), and spectroscopic ellipsometry (SE). XRD spectra and SEM micrographs showed that all films were amorphous and possessed a columnar structure. The ellipsometric angles psi and Delta of as-deposited films were measured by a rotating analyzer ellipsometer in the UV-visible-near infrared range (0.63-6.18 eV) and by an infrared Fourier transform rotating compensator ellipsometer in the 500-5200 cm(-1) wavenumber range. SE measurements were performed at angles of incidence of from 50 degrees to 70 degrees. Parametric models were used to extract thicknesses of the thin films and overlayers of NixW1-x oxide at different compositions, band gaps and optical constants. Features in the optical spectra of the NixW1-x oxides were compared with previous data on tungsten oxide, nickel oxide and nickel tungstate.

Keywords
Tungsten oxide, Nickel oxide, Ellipsometry
National Category
Physical Sciences Engineering and Technology
Research subject
Engineering Science with specialization in Solid State Physics
Identifiers
urn:nbn:se:uu:diva-139785 (URN)10.1016/j.tsf.2010.11.089 (DOI)000289174200076 ()
Note

5th International Conference on Spectroscopic Ellipsometry, MAY 23-29, 2010,Albany, NY

Available from: 2011-09-21 Created: 2010-12-29 Last updated: 2017-12-11Bibliographically approved
Valyukh, I., Green, S., Granqvist, C.-G., Niklasson, G., Valyukh, S. & Arwin, H. (2011). Optical properties of thin films of mixed Ni–W oxide made by reactive DCmagnetron sputtering. Thin Solid Films, 519(9), 2914-2918
Open this publication in new window or tab >>Optical properties of thin films of mixed Ni–W oxide made by reactive DCmagnetron sputtering
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2011 (English)In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 519, no 9, p. 2914-2918Article in journal (Refereed) Published
Abstract [en]

Thin films of NixW1−x oxides with x=0.05, 0.19, 0.43 and 0.90 were studied. Films with thicknesses in the range 125–250 nm were deposited on silicon wafers at room temperature by reactive DC magnetron co-sputtering from targets of Ni and W. The films were characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM), and spectroscopic ellipsometry (SE). XRD spectra and SEMmicrographs showed that all films were amorphous and possessed a columnar structure. The ellipsometric angles Ψ and Δ of as-deposited films were measured by a rotating analyzer ellipsometer in the UV–visible-near infrared range (0.63–6.18 eV) and by an infrared Fourier transform rotating compensator ellipsometer in the 500–5200 cm−1 wavenumber range. SE measurementswere performed at angles of incidence of from50 ° to 70 °. Parametricmodelswere used to extract thicknesses of the thin films and overlayers of NixW1−x oxide at different compositions, band gaps and optical constants. Features in the optical spectra of the NixW1−x oxideswere compared with previous data on tungsten oxide, nickel oxide and nickel tungstate.

National Category
Materials Engineering
Identifiers
urn:nbn:se:uu:diva-178579 (URN)10.1016/j.tsf.2010.11.089 (DOI)
Available from: 2012-07-31 Created: 2012-07-31 Last updated: 2018-08-30Bibliographically approved
Granqvist, C.-G., Bayrak Pehlivan, I., Green, S., Lansåker, P. & Niklasson, G. A. (2011). Oxide-based electrochromics: Advances in materials and devices.. In: Materials Research Society Symposium Proceedings, vol. 1328: . Paper presented at Materials Research Society Conference (pp. 11-22). Materials Research Society
Open this publication in new window or tab >>Oxide-based electrochromics: Advances in materials and devices.
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2011 (English)In: Materials Research Society Symposium Proceedings, vol. 1328, Materials Research Society, 2011, p. 11-22Conference paper, Published paper (Refereed)
Place, publisher, year, edition, pages
Materials Research Society, 2011
Series
Materials research Society Symposium proceedings ; 1328
National Category
Condensed Matter Physics Engineering and Technology
Research subject
Engineering Science with specialization in Solid State Physics
Identifiers
urn:nbn:se:uu:diva-187702 (URN)
Conference
Materials Research Society Conference
Available from: 2012-12-10 Created: 2012-12-10 Last updated: 2014-12-15
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