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Band alignment at the ZrO2/Si(100) interface studied by photoelectron and x-ray absorption spectroscopy
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
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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2007 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 101, no 10, 104120- p.Article in journal (Refereed) Published
Abstract [en]

We present measurements of the Zr and Si core level photoelectron binding energies relative to the Fermi level and the vacuum level under a ZrO2 growth series on Si(100). It is shown that the Zr core level binding energy is most properly referenced to the local vacuum level already from the monolayer regime. This confirms the insulating properties of ZrO2. The Si core levels are referenced to the Fermi level and undergo shifts consistent with the disappearance of the mid-band-gap states originating from the (2×1) reconstruction on the clean Si(100) surface. The use of O 1s x-ray absorption spectroscopy (XAS) to determine the location of the conduction band edge of ZrO2 is discussed with the aid of ab initio calculations. It is demonstrated that the conduction band edge is located at the XAS peak position and that the position relative to the valence band can be determined by aligning the O 1s XAS spectrum to the O 1s photoelectron spectrum. The study thus establishes that photoelectron spectroscopy in conjunction with x-ray absorption spectroscopy forms a most powerful tool for studies of the band alignment at metal oxide-silicon interfaces.

Place, publisher, year, edition, pages
2007. Vol. 101, no 10, 104120- p.
Keyword [en]
Clean metal, semiconductor, and insulator surfaces, X-ray absorption spectra, Crystal binding; cohesive energy, Total energy and cohesive energy calculations
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:uu:diva-94948DOI: 10.1063/1.2738402ISI: 000246891500120OAI: oai:DiVA.org:uu-94948DiVA: diva2:168980
Available from: 2006-10-13 Created: 2006-10-13 Last updated: 2017-12-14Bibliographically approved
In thesis
1. Electronic Properties of Metal Oxide Films Studied by Core Level Spectroscopy
Open this publication in new window or tab >>Electronic Properties of Metal Oxide Films Studied by Core Level Spectroscopy
2006 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In this dissertation core level electron spectroscopy has been employed to study various aspects of metal oxide films grown under ultra-high vacuum conditions.

Studies on in situ ion insertion of lithium into thin TiO2 systems were performed. The electronic and geometric properties are investigated in detail, along with an estimation of charge transfer from Li to Ti.

A detailed study of chemical vapour deposition of ZrO2 on Si(100)-(2x1) was performed. ZrO2 is found to be an insulator, i.e. its electronic levels are decoupled from the substrate and the Zr levels are best referenced to the local vacuum level. The alignment of the valence and conduction band has been determined.

Combinatorial chemical vapour deposition of TiO2 and ZrO2 on Si(100)-(2x1) was realized. A film with graded stoichiometry consisting of pure TiO2 and ZrO2 on the opposing ends and mixed composition of both oxides in the middle was obtained. A detailed study of the electronic levels revealed that ZrO2 remains an insulator in the monolayer regime and that modification of ZrO2 with a small amount of TiO2 leads to a more symmetric alignment of the bands relative to Si.

The influence of a core hole on the O 1s x-ray absorption spectrum in TiO2 and ZrO2 is elucidated. Supported by O 1s photoemission measurements and ab initio calculations it is concluded that the static final state picture as well as dynamical threshold effects must be considered in order to determine the location of the conduction band minimum within the XAS framework.

Finally a Co modified Co:ZnO film was shown to display ferromagnetic properties. It could be evidenced that Co with oxygen as nearest neighbours was responsible for the magnetism and not metallic Co.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2006. 69 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 228
Keyword
Physics, electron spectroscopy, metal oxide, chemical vapour deposition, ion insertion, metal organic, band alignment, zirconium, titanium, silicon, high k, Fysik
Identifiers
urn:nbn:se:uu:diva-7180 (URN)91-554-6673-7 (ISBN)
Public defence
2006-11-03, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 10:15
Opponent
Supervisors
Available from: 2006-10-13 Created: 2006-10-13 Last updated: 2011-02-10Bibliographically approved

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