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Dielectric study of thin films of Ta2O5 and ZrO2
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science.ORCID iD: 0000-0002-5496-9664
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2001 (English)In: IEEE transactions on dielectrics and electrical insulation, ISSN 1070-9878, E-ISSN 1558-4135, Vol. 8, no 4, 648-651 p.Article in journal (Refereed) Published
Abstract [en]

Electronic conduction in sputtered Ta2O5 and ZrO2 thin films have been studied using impedance spectroscopy, isothermal transient ionic current, and current-voltage measurements. The dielectric properties of Ta2O5 were shown to be sensitively dependent on deposition parameters with two different frequency responses: a flat loss behavior with very low DC conductivity, or a relaxation peak together with a somewhat higher DC conductivity. ZrO2 has different dielectric properties when fresh, i.e. newly deposited, or aged. A fresh sample arbitrarily can show two different behaviors, consisting of a DC conductivity with a relaxation peak superimposed on it. The DC conductivity shows either of two different values. The aged sample has a lower permittivity and DC conductivity, and the relaxation peak is found at much lower frequencies. Fresh samples of ZrO2 also show switching behavior

Place, publisher, year, edition, pages
2001. Vol. 8, no 4, 648-651 p.
National Category
Medical and Health Sciences Engineering and Technology
Identifiers
URN: urn:nbn:se:uu:diva-89904DOI: 10.1109/94.946718OAI: oai:DiVA.org:uu-89904DiVA: diva2:161754
Available from: 2002-05-15 Created: 2002-05-15 Last updated: 2017-12-14Bibliographically approved
In thesis
1. Charged Particle Transport: As Information Source about Ion Conductors, Dielectric Materials, and Drug Delivery Systems
Open this publication in new window or tab >>Charged Particle Transport: As Information Source about Ion Conductors, Dielectric Materials, and Drug Delivery Systems
2002 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis treats charged particle transport, mostly in solid materials but also, to some extent, in aqueous media. Three major types of materials have been investigated; dielectric materials, ion conductors, and drug-delivery systems.

The frequency-dependent dielectric permittivity of sputtered amorphous thin film tantalum oxide (Ta2O5) has been determined by using impedance spectroscopy. A new interpolation formula has been derived, that interpolates between the two power-law regions at low and high frequencies usually observed in the dielectric spectrum. This formula is based on a regular-singular-point (RSP) analysis of the conduction process, and the power-laws in the dielectric spectrum are interpreted in terms of RSPs of the underlying rate equation for the corresponding polarization-current response function.

Lithium transport properties of Ta2O5 have been analyzed by using the galvanostatic intermittent titration technique and by isothermal transient ionic current measurements. Chemical and component diffusion coefficients for intercalated lithium have been extracted. Moreover, the ion conduction process has been analyzed theoretically, and expressions for transient ionic currents derived, both for single ion-conducting layers and for three-layered structures of ion conductors.

Electrical measurement techniques have also been applied to pharmaceutical systems. The alternating ionic current technique has been developed as a tool for determining the release of electrically charged drug substances in aqueous media. Tablets made of agglomerated micronized cellulose have been investigated, and sodium chloride has been used as a model drug. An attempt has been made to describe the combined drug dissolution and drug release processes in mathematical terms.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2002. 82 p.
Series
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1104-232X ; 725
Keyword
Materials science, Materialvetenskap
National Category
Materials Engineering
Research subject
Engineering Science
Identifiers
urn:nbn:se:uu:diva-2103 (URN)91-554-5347-3 (ISBN)
Public defence
2002-06-07, the Hägg Lecture Hall at the Ångström Laboratory, Uppsala, 09:30
Opponent
Available from: 2002-05-15 Created: 2002-05-15Bibliographically approved
2. Charge Transport in Transition Metal Oxide Thin Films and Electrochromic Devices
Open this publication in new window or tab >>Charge Transport in Transition Metal Oxide Thin Films and Electrochromic Devices
2002 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Thin film devices for windows, mirrors, space applications and other purposes, have become an essential part of modern technology. A great advantage with a thin film device is the small amount of material used and the compact volume of the device. Dynamic control of thin film device properties is usually obtained by the application of a potential with a resulting charge transport. To understand this charge transport, thus become of great importance to improve, develop, and invent new thin film devices.

Charge transport in transition metal oxide thin films and electrochromic devices have been studied in this thesis using dielectric and electrochemical methods. The dielectric methods used are impedance spectroscopy, the isothermal transient ionic current technique and current-voltage measurements. The electrochemical methods include the galvanostatic intermittent titration technique and electrochemical impedance spectroscopy.

Ion intercalation parameters have been obtained for sputtered and ALD ZrO2 and sputtered TiO2, and the ion conduction processes have been analysed. The dielectric permittivity of as-deposited as well as intercalated thin films of ZrO2 and TiO2 have been studied and electron conduction mechanisms in as-deposited films deduced. From the impedance spectroscopy it is found that the dielectric response changes drastically upon ion intercalation. The complex dielectric response suggests different relaxation processes being important at different levels of intercalation and an explanation built on defect induced dipoles is proposed. Moreover, ion transport in electrochromic devices has been studied. The transient ionic current has been analysed to extract transport parameters both in single layers and whole devices and a deeper understanding of the ionic motion has been achieved.

Place, publisher, year, edition, pages
Uppsala: Materialvetenskap, 2002. 50 p.
Series
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1104-232X ; 779
Keyword
Engineering physics, Teknisk fysik
National Category
Other Engineering and Technologies
Research subject
Solid State Physics
Identifiers
urn:nbn:se:uu:diva-3030 (URN)91-554-5473-9 (ISBN)
Public defence
2002-12-06, Polhemsalen, Uppsala, 09:30 (English)
Opponent
Available from: 2002-11-15 Created: 2002-11-15 Last updated: 2015-09-09Bibliographically approved

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Frenning, GöranStrømme Mattsson, MariaNiklasson, Gunnar A

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