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

Direct link
BETA
Bruckner, Barbara
Publications (10 of 12) Show all publications
Bruckner, B., Bauer, P. & Primetzhofer, D. (2020). Neutralization of slow helium ions scattered from single crystalline aluminum and tantalum surfaces and their oxides. Surface Science, 691, Article ID 121491.
Open this publication in new window or tab >>Neutralization of slow helium ions scattered from single crystalline aluminum and tantalum surfaces and their oxides
2020 (English)In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 691, article id 121491Article in journal (Refereed) Published
Abstract [en]

We investigated the impact of surface oxygen on the ion yield for He+ ions scattered from different single crystalline surfaces in low-energy ion scattering. Initially clean Al(111) and Ta(111) were exposed to molecular oxygen and ion spectra for different oxidation stages and different primary energies were recorded. A comparison of ion yields normalized to the differential scattering cross section as well as experimental factors allows obtaining information about the influence of oxygen on charge exchange processes. The decrease in the ion yield of both metals with exposure cannot be explained by different surface coverages exclusively, but requires the neutralization efficiency to be dependent on the chemical structure of the surface. For Ta, additionally, a different energy dependency of the ion yield obtained in the metal and oxide occurs. The ion yield for O shows in both surfaces a significantly weaker energy dependency than the investigated metals.

Keywords
Low energy ion scattering, Ion yields, Charge exchange, Oxygen exposure, Al(111), Ta(111)
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-394735 (URN)10.1016/j.susc.2019.121491 (DOI)
Available from: 2019-10-09 Created: 2019-10-09 Last updated: 2019-10-28Bibliographically approved
Gründlinger, P., Györök, M., Wolfmayr, S., Breuer, T., Primetzhofer, D., Bruckner, B., . . . Wagner, T. (2019). Aggregation of Au(i)-complexes on amorphous substrates governed by aurophilicity. Dalton Transactions, 48(39), 14712-14723
Open this publication in new window or tab >>Aggregation of Au(i)-complexes on amorphous substrates governed by aurophilicity
Show others...
2019 (English)In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 48, no 39, p. 14712-14723Article in journal (Refereed) Published
Abstract [en]

In single crystals of 2-naphthylisonitrile-gold(i)-halide (halide = Cl, Br, I) complexes, AuMIDLINE HORIZONTAL ELLIPSISAu distances are found to be significantly shorter than twice the van der Waals radius, indicating attractive interactions between gold atoms in adjacent molecules. In the particular case of the studied 2-naphthylisonitrile-gold(i) complexes, homodimers are the common structural motifs, in which the linearly coordinated gold exhibits a crossed swords arrangement with the Au atoms of two molecules being at the intersection point. The crossed swords motif is preserved upon physical vapour deposition of both the chlorine and bromine derivatives on amorphous substrates like glass and glassy carbon. The determined activation energies of desorption for the chlorine (0.9 eV) and the bromine (1.2 eV) derivative are comparable to that of unsubstituted naphthalene. Using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and ion scattering (RBS), we confirmed the chemical integrity of the molecules in thin films and revealed the orientation of the crossed swords dimers with respect to the substrate surface.

Place, publisher, year, edition, pages
ROYAL SOC CHEMISTRY, 2019
National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:uu:diva-396704 (URN)10.1039/c9dt03049b (DOI)000489155800017 ()31539005 (PubMedID)
Funder
Swedish Research Council, 821-2012-5144Swedish Foundation for Strategic Research , RIF14-0053
Available from: 2019-11-08 Created: 2019-11-08 Last updated: 2019-11-08Bibliographically approved
Tran, T., Jablonka, L., Bruckner, B., Rund, S., Roth, D., Sortica, M. A., . . . Primetzhofer, D. (2019). Electronic interaction of slow hydrogen and helium ions with nickel-silicon systems. Physical Review A: covering atomic, molecular, and optical physics and quantum information, 100(3), Article ID 032705.
Open this publication in new window or tab >>Electronic interaction of slow hydrogen and helium ions with nickel-silicon systems
Show others...
2019 (English)In: Physical Review A: covering atomic, molecular, and optical physics and quantum information, ISSN 2469-9926, E-ISSN 2469-9934, Vol. 100, no 3, article id 032705Article in journal (Refereed) Published
Abstract [en]

Electronic stopping cross sections (SCSs) of nickel, silicon, and nickel-silicon alloys for protons and helium (He) ions are studied in the regime of medium- and low-energy ion scattering, i.e., for ion energies in the range from 500 eV to 200 keV. For protons, at velocities below the Bohr velocity the deduced SCS is proportional to the ion velocity for all investigated materials. In contrast, for He ions nonlinear velocity scaling is observed in all investigated materials. Static calculations using density functional theory (DFT) available from the literature accurately predict the SCS of Ni and Ni-Si alloy in the regime with observed velocity proportionality. At higher energies, the energy dependence of the deduced SCS of Ni for protons and He ions agrees with the prediction by recent time-dependent DFT calculations. The measured SCS of the Ni-Si alloy was compared to the SCS obtained from Bragg's rule based on SCS for Ni and Si deduced in this study, yielding good agreement for protons, but systematic deviations for He projectiles, by almost 20%. Overall, the obtained data indicate the importance of nonadiabatic processes such as charge exchange for proper modeling of electronic stopping of, in particular, medium-energy ions heavier than protons in solids.

National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-394745 (URN)10.1103/PhysRevA.100.032705 (DOI)000485188600002 ()
Funder
Swedish Research Council, 821-2012-5144Swedish Research Council, 2017-00646_9Swedish Foundation for Strategic Research , RIF14-0053
Available from: 2019-10-09 Created: 2019-10-09 Last updated: 2019-10-22Bibliographically approved
Bruckner, B. (2019). New aspects of electronic interactions of keV ions with matter. (Doctoral dissertation). Uppsala: Acta Universitatis Upsaliensis
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
Sortica, M. A., Paneta, V., Bruckner, B., Lohmann, S., Nyberg, T., Bauer, P. & Primetzhofer, D. (2019). On the Z(1)-dependence of electronic stopping in TiN. Scientific Reports, 9, Article ID 176.
Open this publication in new window or tab >>On the Z(1)-dependence of electronic stopping in TiN
Show others...
2019 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 9, article id 176Article in journal (Refereed) Published
Abstract [en]

We present a thorough experimental study of electronic stopping of H, He, B, N, Ne and Al ions in TiN with the aim to learn about the energy loss mechanisms of slow ions. The energy loss was measured by means of time-of-flight medium-energy ion scattering. Thin films of TiN on silicon with a delta-layer of W at the TiN/Si interface were used as targets. We compare our results to non-linear density functional theory calculations, examining electron-hole pair excitations by screened ions in a free electron gas in the static limit, with a density equivalent to the expected value for TiN. These calculations predict oscillations in the electronic stopping power for increasing atomic number Z(1) of the projectile. An increasing discrepancy between our experimental results and predictions by theory for increasing Z(1) was observed. This observation can be attributed to contributions from energy loss channels different from electron-hole pair excitation in binary Coulomb collisions.

Place, publisher, year, edition, pages
NATURE PUBLISHING GROUP, 2019
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-375865 (URN)10.1038/s41598-018-36765-7 (DOI)000455951300024 ()30655585 (PubMedID)
Funder
Swedish Foundation for Strategic Research , RIF14-0053
Available from: 2019-02-04 Created: 2019-02-04 Last updated: 2019-02-04Bibliographically approved
Bruckner, B., Bauer, P. & Primetzhofer, D. (2019). The impact of surface oxidation on energy spectra of keV ions scattered from transition metals. Applied Surface Science, 479, 1287-1292
Open this publication in new window or tab >>The impact of surface oxidation on energy spectra of keV ions scattered from transition metals
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
Keywords
Surface oxides, Transition metals, Low energy ion scattering, Ion yield
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-382807 (URN)10.1016/j.apsusc.2018.12.210 (DOI)000464931800152 ()
Available from: 2019-05-07 Created: 2019-05-07 Last updated: 2019-10-28Bibliographically approved
Bruckner, B., Roth, D., Goebl, D., Bauer, P. & Primetzhofer, D. (2018). A note on extracting electronic stopping from energy spectra of backscattered slow ions applying Bragg's rule. Paper presented at 22nd International Workshop on Inelastic Ion-Surface Collisions, SEP 17-22, 2017, Dresden, GERMANY. Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 423, 82-86
Open this publication in new window or tab >>A note on extracting electronic stopping from energy spectra of backscattered slow ions applying Bragg's rule
Show others...
2018 (English)In: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, ISSN 0168-583X, E-ISSN 1872-9584, Vol. 423, p. 82-86Article in journal (Refereed) Published
Abstract [en]

Electronic stopping measurements in chemically reactive targets, e.g., transition and rare earth metals are challenging. These metals often contain low Z impurities, which contribute to electronic stopping. In this article, we present two ways how one can correct for the presence of impurities in the evaluation of proton and He stopping in Ni for primary energies between 1 and 100 keV, either considering or ignoring the contribution of the low Z impurities to multiple scattering. We find, that for protons either method leads to concordant results, but for heavier projectiles, e.g. He ions, the influence on multiple scattering must not be neglected.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE BV, 2018
Keywords
Low energy ion scattering, Electronic stopping, Bragg's rule
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:uu:diva-356188 (URN)10.1016/j.nimb.2018.02.005 (DOI)000430901400013 ()
Conference
22nd International Workshop on Inelastic Ion-Surface Collisions, SEP 17-22, 2017, Dresden, GERMANY
Available from: 2018-07-31 Created: 2018-07-31 Last updated: 2019-10-28Bibliographically approved
Moro, M. V., Bruckner, B., Grande, P. L., Tabacniks, M. H., Bauer, P. & Primetzhofer, D. (2018). Stopping cross section of vanadium for H+ and He+ ions in a large energy interval deduced from backscattering spectra. Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 424, 43-51
Open this publication in new window or tab >>Stopping cross section of vanadium for H+ and He+ ions in a large energy interval deduced from backscattering spectra
Show others...
2018 (English)In: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, ISSN 0168-583X, E-ISSN 1872-9584, Vol. 424, p. 43-51Article in journal (Refereed) Published
Abstract [en]

We have experimentally determined electronic stopping cross sections of vanadium for 50-2750 keV protons and for 250-6000 keV He ions by relative measurements in backscattering geometry. To check the consistency of the employed procedure we investigate how to define adequate reference stopping cross section data and chose different reference materials. To proof consistency of different reference data sets, an intercomparison is performed to test the reliability of the evaluation procedure for a wide range of energies. This process yielded consistent results. The resulting stopping cross section data for V are compared to values from the IAEA database, to the most commonly employed semi-empirical program SRIM, and to calculations according to CasP. For helium, our results show a significant deviation of up to 10% with respect to literature and to SRIM, but are in very good agreement with the CasP predictions, in particular when charge-exchange processes are included in the model.

Keywords
Stopping power, Vanadium, Bragg peak, Proton, Helium, Charge-exchange processes
National Category
Subatomic Physics
Identifiers
urn:nbn:se:uu:diva-357261 (URN)10.1016/j.nimb.2018.03.032 (DOI)000432610900006 ()
Funder
Swedish Research Council, 821-2012-5144Swedish Foundation for Strategic Research , RIF14-0053
Available from: 2018-08-20 Created: 2018-08-20 Last updated: 2018-08-20Bibliographically approved
Sortica, M. A., Paneta, V., Bruckner, B., Lohmann, S., Hans, M., Nyberg, T., . . . Primetzhofer, D. (2017). Electronic energy-loss mechanisms for H, He, and Ne in TiN. Physical Review A: covering atomic, molecular, and optical physics and quantum information, 96(3), Article ID 032703.
Open this publication in new window or tab >>Electronic energy-loss mechanisms for H, He, and Ne in TiN
Show others...
2017 (English)In: Physical Review A: covering atomic, molecular, and optical physics and quantum information, ISSN 2469-9926, E-ISSN 2469-9934, Vol. 96, no 3, article id 032703Article in journal (Refereed) Published
Abstract [en]

The specific energy loss of medium-energy hydrogen, helium, and neon ions in titanium nitride is studied. Electronic stopping cross sections of ions in the energy range of 3-140 keV/amu weremeasured in backscattering geometry using time-of-flight medium-energy ion scattering, from the energy loss experienced in TiN thin films on Si. For the lowest energies, data for H show a strong deviation from Bragg's rule. For hydrogen and Ne ions, electronic stopping exhibits velocity proportionality at ion velocities below 1 a.u. Comparison to density functional theory calculations of the stopping power yields very good agreement for H, while for He and Ne, the experimentally observed electronic stopping power is considerably higher than predicted. For He the extrapolation of the stopping power at low energies points to a nonvanishing energy loss at vanishing ion velocity. The present data can thus be taken as an indication of additional energy- loss processes different from direct electron-hole pair excitation. Furthermore, the results provide reference values for ion-beam-based analysis of TiN, a material with huge technological relevance.

National Category
Atom and Molecular Physics and Optics Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-335209 (URN)10.1103/PhysRevA.96.032703 (DOI)000409427400007 ()
Available from: 2017-12-04 Created: 2017-12-04 Last updated: 2017-12-14Bibliographically approved
Bruckner, B. Electronic interaction of light, keV ions in transition metal nitrides.
Open this publication in new window or tab >>Electronic interaction of light, keV ions in transition metal nitrides
Show others...
(English)In: Article in journal (Refereed) Submitted
Keywords
electronic stopping, low and medium energy ion scattering, transition metal nitrides, HfN, ZrN, TiN, VN, CrN
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-395284 (URN)
Available from: 2019-10-16 Created: 2019-10-16 Last updated: 2019-10-28
Organisations

Search in DiVA

Show all publications