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Electronic structure studies of V6O13 by soft X-ray emission spectroscopy: band-like and excitonic vanadium states
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics II.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
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2004 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 69, no 12, 125103- p.Article in journal (Refereed) Published
Abstract [en]

Resonant soft x-ray emission (SXE) spectra of the mixed valence vanadium oxide V6O13 have been recorded for a series of excitation energies across the V L-absorption band. Resonant excitation allows one to distinguish between charge neutral low-energy excitations and continuum-excited, more band-like V 3d valence band states in the spectra. We find that the V L-emission spectra of V6O13 consist of two distinct components that can be assigned to nearly pure V 3d states, and to V 3dstates that are strongly hybridized with O 2p states, respectively. Band structure calculations of the density functional theory support the assignment of these features. At threshold excitation the V L-emission spectra of V6O13 show strong signatures from excitonic states, the energy dependence of which shows Raman-like behavior. We compare these spectral features in the resonant SXE spectra with cluster model calculations and assign them to dd excitations and charge-transfer excitations, respectively. Finally, we discuss changes in the V L-absorption and emission spectra that take place when changing the sample temperature from 295 K to 120 K. We relate the changes to redistributions in the V 3d partial density of states, which occur at the transition temperature for the metal-semiconductor-transition TMST=150K and find support in our temperature dependent band structure calculations.

Place, publisher, year, edition, pages
2004. Vol. 69, no 12, 125103- p.
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:uu:diva-91861DOI: 10.1103/PhysRevB.69.125103OAI: oai:DiVA.org:uu-91861DiVA: diva2:164727
Available from: 2004-04-29 Created: 2004-04-29 Last updated: 2017-12-14Bibliographically approved
In thesis
1. Resonant Soft X-Ray Emission Spectroscopy of Vanadium Oxides and Related Compounds
Open this publication in new window or tab >>Resonant Soft X-Ray Emission Spectroscopy of Vanadium Oxides and Related Compounds
2004 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Resonant Mjukröntgenemissionsspektroskopi av Vanadinoxider och Relaterade Föreningar
Abstract [en]

This thesis addresses the electronic structure of vanadium and copper oxides using soft X-ray absorption (SXA) spectroscopy and resonant inelastic X-ray scattering (RIXS) at high brightness synchrotron radiation sources. In RIXS incident photons, tuned to the energy of specific absorption resonances, are inelastically scattered leaving behind a low energy valence excitation in the system studied. Effects of electron localization are reflected by the occurrence of low-energy excitations in form of dd- and charge-transfer excitations that are modelled by cluster calculations. Band-like states are dominating when the intermediate core excited state is delocalized.

RIXS at V 2p and O 1s resonances has been used to study the electronic structure of the monovalent vanadium oxides VO2 and V2O3, and of the mixed valence compounds, NaV2O5 and V6O13. For NaV2O5 and V6O13 significant contributions from localized low-energy excitations reflect the partly localized character of their valence band electronic structure, whereas VO2 and V2O3 appear mostly as band-like. Effects of carrier doping are addressed for the case of Mo doping into VO2 and reveal a quasi-rigid band behavior. In the cases of VO2 and V6O13 the temperature dependent metal-insulator transition could be monitored by following the spectral evolution of bands originating from V 3d and V 3d - O2p hybridized states. For Na2V3O7 nanotubes it was possible to selectively probe states from the apical and the basal oxygen sites of VO5 pyramids that constitute these nanotubes. Furthermore, the RIXS technique has been demonstrated to be highly valuable in characterizing the charge transfer processes that accompany lithium insertion into vanadium oxide battery cathodes. Finally, for insulating cuprates RIXS at O 1s, Cu 3p and Cu 3s resonances has been recorded at high-resolution for the detailed investigation of crystal field excitations.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2004. 76 p.
Series
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1104-232X ; 987
Keyword
Physics, vanadium oxides, Li-battery, cathode materials, copper oxides, soft X-ray absorption, soft X-ray emission, resonant inelastic X-ray scattering, cluster model calculations, Fysik
National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-4290 (URN)91-554-5987-0 (ISBN)
Public defence
2004-05-24, Polhemsalen, Ångström Laboratory, Lägerhyddsvägen 1, Uppsala, 10:15
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Available from: 2004-04-29 Created: 2004-04-29 Last updated: 2012-10-09Bibliographically approved

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