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
The impact of surface oxidation on energy spectra of keV ions scattered from transition metals
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics. Johannes Kepler Univ Linz, IEP AOP, Altenbergerstr 69, A-4040 Linz, Austria.
Johannes Kepler Univ Linz, IEP AOP, Altenbergerstr 69, A-4040 Linz, Austria.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.ORCID iD: 0000-0002-5815-3742
2019 (English)In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 479, p. 1287-1292Article in journal (Refereed) Published
Abstract [en]

Studying the initial stages of surface oxidation is of great relevance to understand how oxygen alters the physical and chemical properties at the interface of the host material to the environment and is therefore, crucial for improvement in manifold technological applications. We investigated the influence of surface oxygen on ion spectra recorded for keV noble gas ions backscattered from metal surfaces in low energy ion scattering (LEIS). Initially pure Zn and Ta surfaces, chosen for their well-characterized properties in ion-neutralization in LEIS, have been oxidized and ion spectra for pure and oxidized surfaces have been compared. Oxygen on the surface significantly influences shape and intensity of the backscattered ion spectrum at all energies: for both metal systems, the surface scattered ion yield of the metal is drastically decreasing under oxygen presence. The observed decrease, however, cannot be explained by the reduction in the surface areal density of the metal constituents exclusively. At least for Zn an additional significant change in charge exchange behavior is necessary to explain the observations. In contrast to the generally observed decrease in the yield of ions scattered from the outermost surface, the change in shape and intensity of the reionization background are found to show opposing trends and different energy dependencies for Zn and Ta.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE BV , 2019. Vol. 479, p. 1287-1292
Keywords [en]
Surface oxides, Transition metals, Low energy ion scattering, Ion yield
National Category
Materials Chemistry
Identifiers
URN: urn:nbn:se:uu:diva-382807DOI: 10.1016/j.apsusc.2018.12.210ISI: 000464931800152OAI: oai:DiVA.org:uu-382807DiVA, id: diva2:1314145
Available from: 2019-05-07 Created: 2019-05-07 Last updated: 2019-10-28Bibliographically approved
In thesis
1. New aspects of electronic interactions of keV ions with matter
Open this publication in new window or tab >>New aspects of electronic interactions of keV ions with matter
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Low- and medium-energy ion scattering are powerful techniques to perform high-resolution depth profiling with sub-nanometer resolution. Typically, ions with primary energies between a few keV and a few hundred keV are used to probe the sample and backscattered projectiles are detected. To obtain highly accurate composition profiles, knowledge on physical processes governing ion-matter interaction is crucial. Apart from the main (back-)scattering process, which yields a detectable signal, the projectile loses energy in interactions with both electrons and nuclei (stopping) along its path in matter. In all these interactions, also the charge state of the probing particle can be altered. Information on this multitude of interaction mechanisms can be deduced from two different experimental approaches: either in backscattering or transmission geometry. Especially towards lower primary energies, available experimental data are found more scarce. This situation is particularly true for more complex targets, i.e. reactive transition metals and their compounds. This absence of quantitative information on energy loss or charge exchange processes hampers in many cases the quality of characterization despite the high technological relevance of these materials.

To contribute to an improvement of this status quo, this thesis focuses on (i) an analysis of sources of uncertainties in the evaluation of electronic energy loss, (ii) experiments to obtain stopping data for protons and He ions in different reactive samples and (iii) studies of charge exchange between projectile and target.

The first part presents a discussion of two possible sources of systematic errors, i.e. the composition of the investigated sample (thin films of the reactive transition metals often have low Z impurities like H, C, N and O), and deficiencies in the available models for the scattering potential. Concerning impurities in the films, it is shown that a correction according to Bragg's rule yields good agreement with data obtained from clean samples, even for energies down to a few keV, as long as the concentration levels of the impurities are low. In the second part experimentally deduced electronic energy loss data for transition metal nitrides as well as self-supporting Au and W-foils are presented. In the latter study a comparative approach using backscattering and transmission experiments is performed with measurements in both geometries conducted on the same sample, and in the same scattering chamber with only the position of the detector varied. In the final section the influence of surface oxygen on the energy spectra of backscattered ions at primary energies ≤ 5 keV is investigated. Depending on the host material O is found to enhance or suppress sub-surface signals. Additionally, also the change in neutralization efficiency for surface oxides in comparison to clean metal surfaces is studied for single crystalline Al(111) and Ta(111).

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2019. p. 61
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1876
Keywords
ToF-MEIS, LEIS, electronic stopping, charge exchange, scattering potential
National Category
Condensed Matter Physics
Research subject
Physics
Identifiers
urn:nbn:se:uu:diva-395952 (URN)978-91-513-0803-6 (ISBN)
Public defence
2019-12-06, Polhemsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:00 (English)
Opponent
Supervisors
Available from: 2019-11-08 Created: 2019-10-28 Last updated: 2019-11-08

Open Access in DiVA

No full text in DiVA

Other links

Publisher's full text

Authority records BETA

Bruckner, BarbaraPrimetzhofer, Daniel

Search in DiVA

By author/editor
Bruckner, BarbaraPrimetzhofer, Daniel
By organisation
Applied Nuclear Physics
In the same journal
Applied Surface Science
Materials Chemistry

Search outside of DiVA

GoogleGoogle Scholar

doi
urn-nbn

Altmetric score

doi
urn-nbn
Total: 13 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