uu.seUppsala University Publications
Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Electronic transitions induced by short-range structural order in amorphous TiO2
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.ORCID iD: 0000-0002-8279-5163
Show others and affiliations
2016 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 94, no 16, 165129Article in journal (Refereed) Published
Abstract [en]

Several promising applications of amorphous titanium dioxide, aTiO2, have appeared recently, but thecorrelation between electronic properties and atomic short-range structural order is poorly understood. Herein weshow that structural disorder yields local undercoordinated TiOx units which influence electronic hybridization ofTi-[4p] andTi-[3d] orbitals with a lowcrystal-field splitting [E(eg)-E(t2g) = 2.4 ± 0.3 eV]. The short-range orderand electronic properties of aTiO2 thin-film oxides are described through an integrated approach based on x-rayabsorptionexperiments and ab initio computational simulations where the energy splitting of the electronic levelsin the Ti-[4p-3d]manifold are analyzed. Structural disorder provides enough p-d orbitalmixing for the hybridizedelectronic transitions from the Ti-[1s] core level into the [Ti-t2g] and [Ti-eg] bands [1s → 4p-3d excitations],to be allowed. This yields an intense pre-edge structure in the Ti K-edge x-ray-absorption near-edge structurespectrum of aTiO2, which is consistent with the projected density of states on the photoabsorbing Ti atoms.

Place, publisher, year, edition, pages
2016. Vol. 94, no 16, 165129
National Category
Condensed Matter Physics Engineering and Technology
Research subject
Engineering Science with specialization in Solid State Physics
Identifiers
URN: urn:nbn:se:uu:diva-307422DOI: 10.1103/PhysRevB.94.165129ISI: 000385628600004OAI: oai:DiVA.org:uu-307422DiVA: diva2:1046924
Funder
Swedish Research Council, I811Knut and Alice Wallenberg Foundation
Available from: 2016-11-15 Created: 2016-11-15 Last updated: 2017-03-24Bibliographically approved
In thesis
1. Atomic short-range order, optical and electronic properties of amorphous transition metal oxides: An experimental and theoretical study of amorphous titanium aTiO2 and tungsten aWO3 solid thin-film oxides
Open this publication in new window or tab >>Atomic short-range order, optical and electronic properties of amorphous transition metal oxides: An experimental and theoretical study of amorphous titanium aTiO2 and tungsten aWO3 solid thin-film oxides
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Amorphous transition metal oxides [aTMOs], have emerged as innovative functional materials for wide-ranging electronic, optical and energy-related applications. However, no systematic and broadly applicable method exists to assess their atomic-scale correlations, and since the optical and electronic processes are local structure-dependent, still there are not well-stablished mechanisms that suitably explain the physical properties of aTMOs.

This thesis presents experimental and theoretical studies of the atomic short-range order, optical and electronic properties, and state-defects induced by Li+-ion-intercalation and oxygen-vacancies in amorphous titanium aTiO2 and tungsten aWO3 thin-film oxides. Those properties play a key role for application in high energy-density Li+-ion batteries and in switchable dynamical modulation of solar-irradiation transmittance for energy efficient "smart windows", where the disorder-dependent Li+-ion-intercalation and oxygen-vacancy-induced defect-states influence charge-carrier transfer mechanisms. After introducing the scope of this thesis, the fundamental theoretical concepts describing the experimental findings on amorphous solids are reviewed. Thereafter, a comprehensive analysis on the optical absorption phenomena experimentally observed in oxygen-deficient and Li+-ion-intercalated aLixTiO2−y and aLixWO3−y thin-films and a discussion on the electrochromic properties are presented. The optical absorption is described in the framework of the small polaron absorption model.

Finally, a state-of-the-art systematic procedure involving theory and experiment in a self-consistent computational framework is implemented to unveil the atomic-scale structure of aTiO2 and aWO3, and its role for the electronic properties. The procedure is based in Reverse Monte Carlo [RMC] and Finite Difference Method [FDM] simulations of X-ray-Absorption spectra to construct a disordered theoretical model having the same bonding and coordination distribution as the experimental system. Ab-initio molecular dynamics simulations and density functional theory are then used to assess defect-states induced by Li+-ion-intercalation and oxygen-vacancies in aTiO2 and aWO3 oxides.

The schemes introduced in this study offer a consistent route to experimentally and theoretically assess the role of the atomic-scale structure on the optical and electronic properties of aTiO2 and aWO3 and could be extended to the study of other aTMOs. The final results provide crucial insight towards the understanding of optical and electronic mechanisms where disorder-dependent ion-intercalation and oxygen-vacancy-induced localized defect-states influence charge transfer mechanisms of crucial importance for wide ranging optical and energy-related application of aTiO2 and aWO3 oxides.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2017. 150 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1493
Keyword
X-ray-Absorption, Reverse Monte Carlo, Molecular dynamics, Electronic structure
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-318193 (URN)978-91-554-9866-5 (ISBN)
Public defence
2017-05-15, Room Å80101, Lägerhyddsv. 1, Uppsala, 13:15 (English)
Opponent
Supervisors
Available from: 2017-04-24 Created: 2017-03-23 Last updated: 2017-05-05

Open Access in DiVA

No full text

Other links

Publisher's full text

Search in DiVA

By author/editor
Triana, CarlosAraujo, Carlos MoysesAhuja, RajeevNiklasson, Gunnar A.Edvinsson, Tomas
By organisation
Solid State PhysicsMaterials Theory
In the same journal
Physical Review B. Condensed Matter and Materials Physics
Condensed Matter PhysicsEngineering and Technology

Search outside of DiVA

GoogleGoogle Scholar

Altmetric score

Total: 649 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf