Change search
Refine search result
123 1 - 50 of 103
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • apa.csl
  • 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
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1.
    Ahlskog, Markus
    et al.
    University Jyvaskyla, FIN.
    Hokkanen, Matti J.
    University Jyvaskyla, FIN.
    Levshov, Dmitry
    Southern Federal University, RUS..
    Svensson, Krister
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Volodin, Alexander
    Katholieke University Leuven, BEL.
    van Haesendonck, Chris
    Katholieke University Leuven, BEL.
    Individual arc-discharge synthesized multiwalled carbon nanotubes probed with multiple measurement techniques2020In: Journal of Vacuum Science and Technology B: Nanotechnology and Microelectronics, ISSN 2166-2746, E-ISSN 2166-2754, Vol. 38, no 4, article id 042804Article in journal (Refereed)
    Abstract [en]

    Arc-discharge synthesized multiwalled carbon nanotubes (AD-MWNT), or related MWNTs, exhibit a good quality compared to the more common type of MWNT synthesized by catalytic chemical vapor deposition methods. Yet experimental measurements on these are rather few and typically have not correlated data from different measurement techniques. Here, the authors report Raman spectroscopy, scanning probe microscopy, conductivity measurements, and force microscopy on single AD-MWNTs. The results demonstrate the high quality of AD-MWNTs and are compatible with the view of them as the best approximation of MWNTs as an assembly of defect-free concentric individual single-walled carbon nanotubes. The authors also demonstrate conductance measurements over a step on the surface of an AD-MWNT, which is due to an abruptly broken outer layer(s), whereby the interlayer resistance is measured.

  • 2. Andersson, S.
    et al.
    Svensson, Krister
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Dissociation of Physisorbed H_ $$2$$ through Low-Energy Electron Scattering Resonances2010In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 104, p. 216101-216105Article in journal (Refereed)
    Abstract [en]

    Electron induced dissociation of physisorbed H2, HD, and D2 proceeds, as we observe in electron energy-loss measurements of the resulting atomic species, with a high quantum efficiency via the 2Σg+ core excited electron scattering resonances. We find that the predominant decay of the temporary H2- state to the neutral excited 3Σu+ parent state, which is intramolecularly antibonding, provides a sufficiently long-lived channel for dissociation to occur with high probability, even in the proximity of a metal surface.

  • 3.
    Andersson, S.
    et al.
    Department of Physics, Göteborg University.
    Svensson, Krister
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Electron-Induced Desorption of Physisorbed H_ $$2$$ via Resonance Vibrational Excitation2009In: Physical review letters, ISSN 0031-9007, Vol. 102, no Issue 15, p. 156104-Article in journal (Refereed)
    Abstract [en]

    We show by electron energy-loss measurements that desorption of physisorbed H2 and D2 induced by low-energy electrons takes place with large cross sections, predominantly via resonance excitation of the molecule-surface vibrational mode. The observed H2, D2 cross-section ratio supports a picture where rotation-translation conversion of the resonance excited j=0→2 rotational transition contributes to the desorption of H2, while this channel is energetically closed for D2

  • 4.
    Andersson, Stig
    et al.
    Göteborgs Universitet.
    Svensson, Krister
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Excitation and desorption of physisorbed H2 via the 2Σu electron scattering resonance.2017In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 147, p. 114703-1-114703-11, article id 114703Article in journal (Refereed)
    Abstract [en]

    Our high-resolution electron energy-loss measurements concern physisorbed H2 and comprise dif- ferential cross sections for the excitation of the internal H2 modes and the H2-surface bonding mode and their combinations and extend over the electron impact energy range of the classical low-energy H2 2Σu resonance. Comparison with corresponding data for the excitation of the internal modes of gas phase H2 reveals that strong elastic electron reflectivity from the Cu(100) substrate profoundly distorts the inelastic scattering pattern for physisorbed H2. We find that this influence can be corrected for and that the resulting peak cross sections agree with the H2 gas phase data, in accordance with theoretical predictions for the excitation of the internal H2 vibration. We have used corrected cross sections for the rotational mode spectra of physisorbed H2, HD, and D2 in a model concerning elec- tron induced desorption via rotation-translation energy conversion. These spectra include transitions from the ground state as well as excited levels of the physisorption potential well. H2 and HD can desorb from all levels while D2, for energetic reason, can only desorb from the excited levels. This model gives a satisfactory account of the observed desorption cross sections and predicts character- istic velocity distributions of the desorbing molecules. The cross section data for H2 and HD reveals that direct bound-free transitions also contribute to the electron induced desorption. 

    Download full text (pdf)
    fulltext
  • 5.
    Anselmo, Ana Sofia
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Dzwilewski, Andrzej
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Rysz, Jakub
    M. Smoluchowski Insitute of Physics, Jagiellonian University, Reymonta 4, Krakow 30–059, Poland.
    Bernasik, Andrzej
    Faculty of Physics and Applied Computer Science, AGH-University of Science and Technology, Al. Mickiewicza 30, Krakow 30–059, Poland.
    Budkowski, Andrzej
    M. Smoluchowski Insitute of Physics, Jagiellonian University, Reymonta 4, Krakow 30–059, Poland.
    Andersson, Mats R.
    Department of Chemical and Biological Engineering, Chalmers University of Technology.
    van Stam, Jan
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Svensson, Krister
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Moons, Ellen
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Characterisation of vertical phase separation in polymer: fullerene blend films for photovoltaics by dSIMS and NEXAFS2011In: E-MRS 2011 Spring Meeting: Bilateral Energy Conference, Malden, MA: John Wiley & Sons, 2011, p. 62-63Conference paper (Refereed)
    Abstract [en]

    Morphological control and characterization of blend films is key in the development of viable polymer solar cells. Spontaneous formation of vertical compositional gradients during solution processing has been shown for polyfluorene:PCBM blends and rationalized with thermodynamic and kinetic models of nucleation and spinodal decomposition.[1, 2] The extent of vertical stratification is affected by polymer side-chain modification aimed at controlling polymer:fullerene miscibility.[3] Here we present high-resolution film morphology results for several polymer:fullerene systems as obtained from near-edge X-ray fine structure spectroscopy (NEXAFS) in partial and in total electron yield modes. Blend films were found to be polymer- enriched at the surface. Dynamic secondary ion mass spectrometry (dSIMS) and NEXAFS give compositional information at different depths, resulting in a more complete picture of the film morphology.

     

  • 6.
    Anselmo, Ana Sofia
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Dzwilewski, Andrzej
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Rysz, Jakub
    M. Smoluchowski Insitute of Physics, Jagiellonian University, Reymonta 4, Krakow 30–059, Poland.
    Budkowski, Andrzej
    M. Smoluchowski Insitute of Physics, Jagiellonian University, Reymonta 4, Krakow 30–059, Poland.
    Svensson, Krister
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    van Stam, Jan
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Moons, Ellen
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Polymer solar cells: Visualizing vertical phase separation in solution-processed films of polymer fullerene blends2012In: Proceedings of the 5th International Symposium Technologies for Polymer Electronics - TPE 12 / [ed] Hans-Klaus Roth, Klaus Heinemann, Ilmenau, Germany: Universitätsverlag Ilmenau , 2012, p. 125-128Conference paper (Refereed)
  • 7.
    Anselmo, Ana Sofia
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Dzwilewski, Andrzej
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Svensson, Krister
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Moons, Ellen
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Molecular Orientation and Composition at the Surface of Spin-Coated Polyfluorene:Fullerene Blend Films2013In: Journal of Polymer Science Part B: Polymer Physics, ISSN 0887-6266, E-ISSN 1099-0488, Vol. 51, no 3, p. 176-182Article in journal (Refereed)
    Abstract [en]

    The surface composition in spin-coated films of polyfluorene:fullerene blends was determined quantitatively by near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. By comparing partial and total electron yield spectra, we found vertical compositional differences in the surface region. Furthermore, the orientation of the polymer chains was investigated by variable-angle NEXAFS. Blend films of poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole] with [6,6]-phenyl-C61-butyric acid methyl ester in two different blend ratios were studied. Results showed polymer enrichment of the surfaces for films with a polymer:fullerene weight ratio of 20:80 and of 50:50, spin-coated from both chlorobenzene and chloroform solutions. The angular dependence of the NEXAFS spectra of the pure polymer films showed a preferential plane-on orientation, which was slightly stronger in the subsurface region than at the surface. In blend films, this orientational preference was less pronounced and the difference between surface and subsurface vanished

  • 8.
    Anselmo, Ana Sofia
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Dzwilewski, Andrzej
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Svensson, Krister
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Moons, Ellen
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Photodegradation of the electronic structure of PCBM and C60 films in air2016In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 652, p. 220-224Article in journal (Refereed)
    Abstract [en]

    Fullerenes are common electron acceptors in organic solar cells. Here the photostability in air of the electronic structures of spin-coated PCBM ([6,6]-phenyl-C61-butyric acid methyl ester) and evaporated C60 films are studied using ultraviolet photoelectron spectroscopy (UPS) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. After exposing these materials in air to simulated sunlight, the filled and empty molecular orbitals are strongly altered, indicating that the conjugated π-system of the C60-cage has degraded. Even a few minutes in normal lab light induces changes. These results stress the importance of protecting fullerene-based films from light and air during processing, operation, and storage.

  • 9.
    Anselmo, Ana Sofia
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Dzwilewski, Andrzej
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Wang, Ergang
    Department of Chemical and Biological Engineering, Chalmers University of Technology.
    Andersson, Mats R.
    Department of Chemical and Biological Engineering, Chalmers University of Technology.
    Hörmann, Ulrich
    Institute of Physics, Augsburg University.
    Opitz, Andreas
    Institute of Physics, Augsburg University.
    van Stam, Jan
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Svensson, Krister
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Moons, Ellen
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Surface Organization in Thin-Films of Conjugated Polymers for Organic Photovoltaics2011Conference paper (Other academic)
  • 10.
    Anselmo, Ana Sofia
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Dzwilewski, Andrzej
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Wang, Ergang
    Chalmers University of Technology.
    Andersson, Mats R.
    Chalmers University of Technology.
    van Stam, Jan
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Svensson, Krister
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Moons, Ellen
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Molecular orientation and composition at the surface of APFO3:PCBM blend films2012In: Hybrid and Organics Photovoltaics Conference: Uppsala, Sweden, 2012 / [ed] Anders Hagfeldt, SEFIN, Castelló (Spain), 2012, p. 278-Conference paper (Refereed)
  • 11.
    Anselmo, Ana Sofia
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Lindgren, Lars
    Department of Chemical and Biological Engineering, Chalmers University of Technology.
    Rysz, Jakub
    Institute of Physics, Jagiellonian University, Poland.
    Bernasik, Andrzej
    Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, Poland.
    Budkowski, Andrzej
    Institute of Physics, Jagiellonian University, Poland.
    Andersson, Mats R.
    Department of Chemical and Biological Engineering, Chalmers University of Technology.
    Svensson, Krister
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    van Stam, Jan
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Moons, Ellen
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Tuning the Vertical Phase Separation in Polyfluorene:Fullerene Blend Films by Polymer Functionalization2011In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 23, no 9, p. 2295-2302Article in journal (Refereed)
    Abstract [en]

    Achieving control over the nanomorphology of blend films of the fullerene derivative [6,6]-phenyl C61-butyric acid methyl ester, PCBM, with light-absorbing conjugated polymers is an important challenge in the development of efficient solution-processed photovoltaics. Here, three new polyfluorene copolymers are presented, tailored for enhanced miscibility with the fullerene through the introduction of polymer segments with modified side chains, which enhance the polymer’s polar character. The composition of the spincoated polymer:PCBM films is analyzed with dynamic secondary ion mass spectrometry (dSIMS). The dSIMS depth profiles demonstrate compositional variations perpendicular to the surface plane, as a result of vertical phase separation, directed by the substrate. These variations propagate to a higher degree through the film for the polymers with a larger fraction of modified side chains. The surface composition of the films is studied by Near-edge X-ray absorption fine structure spectroscopy (NEXAFS). Quantitative analysis of the NEXAFS spectra through a linear combination fit with the spectra of the pure components yields the surface composition. The resulting blend ratios reveal polymer-enrichment of the film surface for all three blends, which also becomes stronger as the polar character of the polymer increases. Comparison of the NEXAFS spectra collected with two different sampling depths shows that the vertical composition gradient builds up already in the first nanometers underneath the surface of the films. The results obtained with this new series of polymers shed light on the onset of formation of lamellar structures in thin polymer:PCBM films prepared from highly volatile solvents

  • 12.
    Anselmo, Ana Sofia
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Lindgren, Lars
    Department of Chemical and Biological Engineering, Chalmers University of Technology.
    Svensson, Krister
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Hörmann, Ulrich
    Institute of Physics, University of Augsburg.
    Brütting, Wolfgang
    Institute of Physics, University of Augsburg.
    van Stam, Jan
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Andersson, Mats R.
    Department of Chemical and Biological Engineering, Chalmers University of Technology.
    Opitz, Andreas
    Institute of Physics, Humboldt University Berlin.
    Moons, Ellen
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Polyfluorene copolymers with functionalized side chains: Opto-electronic properties and solar cell performance2012Manuscript (preprint) (Other academic)
  • 13.
    Anselmo, Ana Sofia
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Moons, Ellen
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Svensson, Krister
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    van Stam, Jan
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Morphology of Thin-Films of Polyfluorene: Fullerene Blends2008In: 1st Portuguese Young Chemists Meeting, PYCheM: Abstracts, 2008, p. 36-36Conference paper (Refereed)
  • 14. Bellman, J.
    et al.
    Svensson, Krister
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Andersson, S.
    Molecular Hydrogen Adsorption at surface adatoms2006In: Journal of Chemical PhysicsArticle in journal (Refereed)
  • 15. Bengtsson, L.
    et al.
    Svensson, Krister
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Hassel, M.
    Bellman, J.
    Persson, M.
    Andersson, S.
    H_{2} adsorbed in a two-dimensional quantum rotor state on a stepped copper surface2000In: Physical Review BArticle in journal (Refereed)
  • 16.
    Bengtsson, P.
    et al.
    Nanofactory Instruments AB.
    Svensson, Krister
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Olin, H.
    Applied scicence and design, Mid Sweden University.
    Von Dorrien, M.
    Nanofactory Instruments AB.
    Control Signal for Inertial Slider2008Patent (Other (popular science, discussion, etc.))
  • 17. Bengtsson, P.
    et al.
    Svensson, Krister
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Olin, H.
    von Dorrien, M.
    Control signal for inertial slider2007Patent (Other (popular science, discussion, etc.))
  • 18.
    Brumboiu, Iulia
    et al.
    Department of Physics and Astronomy, Uppsala University.
    Anselmo, Ana Sofia
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Brena, Barbara
    Department of Physics and Astronomy, Uppsala University.
    Dzwilewski, Andrzej
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Svensson, Krister
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Moons, Ellen
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Near-edge X-ray Absorption Fine Structure Study of the C60-derivative PCBM2013In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 568-569, p. 130-134Article in journal (Refereed)
    Abstract [en]

    The fullerene derivative [6,6]-phenyl-C61-butyric acid methyl ester plays a key role for electron transport in polymer solar cells. We have studied the unoccupied molecular orbitals of PCBM by near edge X-ray absorption fine structure spectroscopy and were able to assign the main resonances to molecular moieties by comparison with calculated sum spectra of individual carbons. We analyzed specifically the origin of the high-energy shoulder to the first π-resonance and identified contributions from the lowest-energy transition of a specific carbon in the phenyl and from transitions to higher unoccupied orbitals of the unmodified carbons in the C60-cage.

  • 19.
    Börjesson, J.
    et al.
    Chalmers University of Technology, Gothenburg.
    Kalabukhov, A.
    Chalmers University of Technology, Gothenburg.
    Svensson, Krister
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Olsson, E.
    Chalmers University of Technology, Gothenburg.
    A method for in-situ electrical measurements of thin film heterostructures using TEM and SEM2008In: EMC 2008 14th European Microscopy Congress 1–5 September 2008, Aachen, Germany 2008: Volume 2: Materials Science / [ed] Silvia Richter, Alexander Schwedt, Berlin, Heidelberg: Springer, 2008, p. 297-298Conference paper (Refereed)
    Abstract [en]

    A method for in-situ measurements of electrical properties of thin film heterostructures using TEM and SEM has been developed. This method allows measurements of the conductance in a thin film heterostructure in a direction along the film planes in thin TEM foils. The advantage is that the properties can be directly correlated to the local atomic structure. The specimens are cross section TEM samples prepared with standard grinding, polishing and ion beam milling techniques

  • 20. Chao, Y.
    et al.
    Svensson, Krister
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Radosavkic, D.
    Dhanak, V.R.
    Siller, L.
    Hunt, M.R.C.
    Photoemission spectroscopy of the evolution of In-terminated InP(100)-2x4 as a function of temperature: surface- and cluster-related In 4d lines2002In: Physical Review BArticle in journal (Refereed)
  • 21. Chao, Y.
    et al.
    Svensson, Krister
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Radosavkic, D.
    Dhanak, V.R.
    Siller, L.
    Hunt, M.R.C.
    Photoemission study of chemisorption of C60 on InP(100)2001In: Physical Review BArticle in journal (Refereed)
  • 22. de Knoop, L.
    et al.
    Svensson, Krister
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Petterson, H.
    Olsson, E.
    Extraction and local probing of individual carbon nanotubes2005Conference paper (Refereed)
  • 23.
    Dzwilewski, Andrzej
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Anselmo, Ana Sofia
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Svensson, Krister
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Moons, Ellen
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Light induced effects in PCBM:P3HT blend films2012In: Hybrid and Organics Photovoltaics Conference: Uppsala, Sweden, 2012 / [ed] Anders Hagfeldt, SEFIN, Castelló (Spain), 2012, p. 155-155Conference paper (Refereed)
  • 24.
    Dzwilewski, Andrzej
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Anselmo, Ana Sofia
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Svensson, Krister
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Zharnikov, Michael
    Moons, Ellen
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    X-ray absorption study of light induced effects in PCBM:P3HT blend films2011In: Photovoltaics at the nanoscale: Hasselt University (Belgium) 24-28 October 2011, Hasselt University, Belgium, 2011, p. 59-59Conference paper (Refereed)
  • 25. Eastham, D A
    et al.
    Edmondson, P.
    Donnelly, S.
    Olsson, E.
    Svensson, Krister
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Bleloch, A.
    Construction of a new type of low-energy scanning electron microscope with atomic resolution2009In: Scanning Microscopy / [ed] Dale E. Newbury; S. Frank Platek; David C. Joy; Michael T. Postek, Monterey: SPIE Digital Library , 2009, p. 73781S-73781SConference paper (Refereed)
    Abstract [en]

    We describe a new type of scanning electron microscope which works by directly imaging the electron field-emission sites on a nanotip. Electrons are extracted from the nanotip through a nanoscale aperture, accelerated in a high electric field and focussed to a spot using a microscale einzel lens. If the whole microscope (accelerating section and lens) and the focal length are both restricted in size to below 10 microns, then computer simulations show that the effects of aberration are extremely small and it is possible to have a system with approximately unit magnification, at electron energies as low as 300 eV. Thus a typical emission site of 1 nm diameter will produce an image of the same size and an atomic emission site with give a resolution of 0.1-0.2 nm (1-2 Å), and because the beam is not allowed to expand beyond 100nm in diameter the depth of field is large and the contribution to the beam spot size from chromatic aberrations is less than 0.02 nm (0.2 Å) for 500 eV electrons. Since it is now entirely possible to make stable atomic sized emitters (nanopyramids) it is expected that this instrument will have atomic resolution. Furthermore the brightness of the beam is determined only by the field-emission and can be up to a million times larger than in a typical (high-energy) electron microscope. The construction of this microscope, based on using a nanotip electron source which is mounted on a nanopositioner so that it can be positioned at the correct point adjacent to the microscope, entrance aperture, is described. In this geometry the scanning is achieved by moving the sample using piezos. Two methods for the construction of the microscope column are reviewed and the results of preliminary tests are described. The advantages of this low energy, bright-beam, electron microscope with atomic resolution are described. It can be used in either scanning mode or diffraction mode. The major advantage over existing microscopes is that because it works at very low energies the elastic backscattering is sensitive to the atomic species and so these can be identified directly without any energy discrimination on the detector. Furthermore it is also possible to use the microscope to do low energy electron diffraction which, because the scattering cross-section is large, can be carried out on single molecules. If these are biological samples such as DNA, proteins and viruses then the low energy means that the radiation damage is minimised. Some possibilities for mounting these samples, which can reduce radiation damage, are discussed. Finally we show a system for producing holograms of single protein molecules

  • 26. Erts, D.
    et al.
    Lohmus, A.
    Lohmus, R.
    Olin, H.
    Pokropivny, A.V.
    Ryen, L.
    Svensson, Krister
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Force interactions and adhesion of gold contacts using a combined atomic force microscope and transmission electron microscope2002In: Applied Surface Science, Vol. 188, no 3, p. 460-Article in journal (Refereed)
  • 27. Eves, B.J.
    et al.
    Festy, F.
    Svensson, Krister
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Palmer, R.E.
    Scanning probbe energy loss spectroscopy: Angular resolved measurements on silicon and graphite surfaces2000In: Applied Physics LettersArticle in journal (Refereed)
  • 28.
    Festy, F.
    et al.
    The University of Birmingham.
    Svensson, Krister
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science. The University of Birmingham.
    Laitenberger, P.
    The University of Birmingham.
    Palmer, R.E.
    The University of Birmingham.
    Imaging surfaces with reflected electrons from a field-emission STM: image contrast mechanisms2001In: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, no 34, p. 1849-Article in journal (Refereed)
    Abstract [en]

    Electrons backscattered from a scanning tunnelling microscope operating in the field emission mode have been collected to produce images of a rough Si(111) surface. We have obtained a spatial resolution of about 40 nm in such images. Comparison between backscattered electron images and topographic images reveals that edge enhancement and shadowing are important contrast mechanisms.

  • 29.
    Flygare, Mattias
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Svensson, Krister
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Accurate determination of electrical conductance in carbon nanostructures2022In: Materials Research Express, E-ISSN 2053-1591, Vol. 9, no 3, article id 035010Article in journal (Refereed)
    Abstract [en]

    Electrical characterization of nanostructures, such as nanotubes and wires, is a demanding task that is vital for future applications of nanomaterials. The nanostructures should ideally be analyzed in a free-standing state and also allow for other material characterizations to be made of the same individual nanostructures. Several methods have been used for electrical characterizations of carbon nanotubes in the past. The results are widely spread, both between different characterizations methods and within the same materials. This raises questions regarding the reliability of different methods and their accuracy, and there is a need for a measurement standard and classification scheme for carbon nanotube materials. Here we examine a two-probe method performed inside a transmission electron microscope in detail, addressing specifically the accuracy by which the electrical conductivity of individual carbon nanotubes can be determined. We show that two-probe methods can be very reliable using a suitable thermal cleaning method of the contact points. The linear resistance of the outermost nanotube wall can thus be accurately determined even for the highest crystallinity materials, where the linear resistance is only a few kΩ/µm. The method can thereby by used as a valuable tool for future classification schemes of various nanotube material classes. 

    Download full text (pdf)
    fulltext
  • 30.
    Flygare, Mattias
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Svensson, Krister
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Influence of crystallinity on the electrical conductivity of individual carbon nanotubes2021In: Carbon Trends, ISSN 2667-0569, Vol. 5, article id 100125Article in journal (Refereed)
    Abstract [en]

    The material properties of graphene and carbon nanotubes are highly sensitive to defects. Future exploitation of these materials will thereby rely on both a detailed understanding and classification schemes for material quality. Here we have used electron diffraction to measure the mean effective crystallite size of individual multiwalled carbon nanotubes, while also probing their electrical resistance. At room temperature we find a drastic shift in linear resistance of two orders of magnitude at a critical grain size of about 11 nm, which we interpret as an effect from quantum confinement and edge effects in the individual crystallites. For the regions above and below the critical grain size value we suggest a scaling model for the electrical conductivity within a single layer of a multiwalled carbon nanotube which connects its electrical conductivity with the effective crystallite size and tube diameter.

    Download full text (pdf)
    fulltext
  • 31.
    Flygare, Mattias
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Svensson, Krister
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Quantifying crystallinity in carbon nanotubes and its influence on mechanical behaviour2019In: Materials Today Communications, ISSN 2352-4928, Vol. 18, p. 39-45Article in journal (Refereed)
    Abstract [en]

    The different fabrication methods that have been developed for making carbon nanotubes will provide materials with different levels of crystallinity. As crystallinity is qualitatively known to have a profound influence on material properties, this raises the need for standardised quantitative analysis. Here we show how transmission electron microscopy can be used to provide quantitative information about effective crystallite sizes in individual nanotubes which we link to the mechanical behaviour of the tubes. The method relies on a thorough analysis of diffraction patterns and a careful extraction of instrumental and sample contributions to the peak shapes. We find that arc-discharge grown tubes have crystallite sizes that are comparable to the circumference of the outer tube walls, while commercial catalytically grown tubes have much smaller crystallites implying that each cylindrical nanotube wall can be thought of as a patchwork of small graphene-like grains. The clear differences in crystallite sizes are then compared to known differences in mechanical behaviour, such as a substantial disparity in stiffness and significantly different behaviours under bending stress.

    Download full text (pdf)
    fulltext
  • 32.
    Ghavanini, Farzan
    et al.
    Department of Microtechnology and Nanoscience, Chalmers University of Technology, 41296 Göteborg, Sweden.
    Jackman, Henrik
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Lundgren, Per
    Department of Microtechnology and Nanoscience, Chalmers University of Technology, 41296 Göteborg, Sweden.
    Svensson, Krister
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Enoksson, Peter
    Department of Microtechnology and Nanoscience, Chalmers University of Technology, 41296 Göteborg, Sweden.
    Direct measurement of bending stiffness and estimation of Young’s modulus of vertically aligned carbon nanofibers2013In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 113, no 19Article in journal (Refereed)
    Abstract [en]

    We have measured the bending stiffness of as-grown vertically aligned carbon nanofibers using atomic force microscopy inside a scanning electron microscope. We show that the assumption of a uniform internal structure is inadequate in describing nanofibers mechanical properties and that a dual phase model is needed. We present a model in which different Young’s moduli are assigned to the inner graphitic core and the outer amorphous carbon shell and show that it provides a better fit to the measurements. We obtain values of 11±8 GPa and 63±14 GPa for the Young’s modulus of the inner core and the outer shell, respectively.

  • 33.
    Ghavanini, Farzan
    et al.
    Chalmers University of Technology.
    Jackman, Henrik
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Svensson, Krister
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Lundgren, Per
    Chalmers University of Technology.
    Enoksson, Peter
    Chalmers University of Technology.
    Direct Measurement of the Young’s Modulus of Individual Vertically Aligned Carbon Nanofibers (VACNFs)2011Conference paper (Refereed)
    Abstract [en]

    Vertically aligned carbon nanofibers (VACNFs) are synthesized in a plasma-enhanced chemical vapor deposition process (PECVD) in which the position, diameter, length, and alignment of individual nanofibers can be controlled accurately. This has provided an unprecedented opportunity to realize a new bottom-up-engineered material with excellent mechanical and electrical properties which could exploit the third dimension at a reasonable cost. VACNFs have been already employed in a number of applications including electron emitters, gene delivery arrays, and nanoelectromechanical systems. However, no direct measurement of the Young’s modulus of VACNFs has been reported yet. Qi et al. have used nanoindentation method to measure the collective response of a forest of VACNFs with a distribution in length and diameter of the constituent nanofibers. Kaul et al., have reported in situ uniaxial compression tests on individual VACNFs but they have not provided enough information to evaluate the accuracy of their measurements. Indirect estimation of the VACNFs Young’s modulus has also been reported by Eriksson et al. from measurements of the resonance frequency of a nanofiber deposited on top of an excitation electrode. Here, we report on direct measurements of VACNFs Young’s modulus using a piezoresistive atomic force microscope (AFM) cantilever implemented inside a scanning electron microscope (SEM). The VACNFs were grown from Ni catalyst seeds, patterned using electron-beam lithography on top of a stoichiometric TiN underlayer. The VACNFs were grown in a commercially available PECVD chamber (AIXTRON BlackMagic™). The nanofibers were approached from the side and pushed at the tip (resembling a cantilever beam) and force-deflection curves were obtained. By calibrating the AFM sensor the bending stiffness of the nanofiber could be determined. The Young’s modulus was then estimated by taking the nanofibers dimensions into account. The sub-nano Newton force precision provided by the AFM force-sensor together with the fact the individual VACNFs could be observed in the SEM simultaneously during the measurements, has enabled us to measure the nanofibers Young’s modulus with a high precision. Preliminary measurements indicate that VACNFs posses a Young’s modulus between 40 to 100 GPa which is comparable to CVD grown carbon nanotubes of similar diameter

  • 34.
    Ghavanni, Farzan
    et al.
    Chalmers, Dept Microtechnol & Nanosci, BioNano Syst Lab, Micro & Nanosyst Grp, SE-41296 Gothenburg, Sweden.
    Lopez-Damian, Maria
    Chalmers, Dept Microtechnol & Nanosci, BioNano Syst Lab, Micro & Nanosyst Grp, SE-41296 Gothenburg, Sweden.
    Rafeian, Damon
    Chalmers, Dept Microtechnol & Nanosci, BioNano Syst Lab, Micro & Nanosyst Grp, SE-41296 Gothenburg, Sweden.
    Svensson, Krister
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Lundgren, Per
    Chalmers, Dept Microtechnol & Nanosci, BioNano Syst Lab, Micro & Nanosyst Grp, SE-41296 Gothenburg, Sweden.
    Enoksson, Peter
    Chalmers, Dept Microtechnol & Nanosci, BioNano Syst Lab, Micro & Nanosyst Grp, SE-41296 Gothenburg, Sweden.
    Controlling the initial phase of PECVD growth of vertically aligned carbon nanofibres on TiN2011In: Sensors and Actuators A-Physical, ISSN 0924-4247, E-ISSN 1873-3069, Vol. 172, no 1, p. 347-358Article in journal (Refereed)
    Abstract [en]

    We explore the growth of vertically aligned carbon nanofibers by plasma enhanced chemical vapor deposition, using lithographically defined Ni catalyst seeds on TiN. TiN is selected for being an electrically conducting diffusion barrier suitable for the realization of electronic devices. We show that the rate of Ni diffusion correlates to both the level of oxygen content in the TiN film and to the film resistivity. The synthesis of the nanofibers was characterized using electron microscopy with an emphasis on three growth parameters: substrate temperature, plasma power, and chamber pressure. We propose that a catalyst surface free from carbon deposits throughout the process will induce diffusion-limited growth. The growth will shift towards a supply-limited process when the balance between acetylene, as the effective carbon bearing gas, and atomic hydrogen, as the main etching agent, is skewed in favor of acetylene. This determines whether the dominating growth mode will be vertically aligned tip-type or disordered base-type, by affecting the competition between the formation of the first graphitic sheets on the catalyst surface and at the catalyst-substrate interface

  • 35.
    Hansson, Josef
    et al.
    Chalmers University of Technology.
    Nylander, Andreas
    Chalmers University of Technology.
    Flygare, Mattias
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Svensson, Krister
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Ye, Lilei
    SHT Smart High Tech AB, Gothenburg.
    Nilsson, Torbjörn
    Chalmers University of Technology.
    Fu, Yifeng
    Chalmers University of Technology.
    Liu, Johan
    Chalmers University of Technology.
    Effects of high temperature treatment of carbon nanotube arrays on graphite: Increased crystallinity, anchoring and inter-tube bonding2020In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 31, no 45, article id 455708Article in journal (Refereed)
    Abstract [en]

    Thermal treatment of carbon nanotubes (CNTs) can significantly improve their mechanical, electrical and thermal properties due to reduced defects and increased crystallinity. In this work we investigate the effect of annealing at 3000 degrees C of vertically aligned CNT arrays synthesized by chemical vapor deposition (CVD) on graphite. Raman measurements show a drastically reduced amount of defects and, together with transmission electron microscope (TEM) diffraction measurements, an increased average crystallite size of around 50%, which corresponds to a 124% increase in Young's modulus. We also find a tendency for CNTs to bond to each other with van der Waals (vdW) forces, which causes individual CNTs to closely align with each other. This bonding causes a densification effect on the entire CNT array, which appears at temperatures >1000 degrees C. The densification onset temperature corresponds to the thermal decomposition of oxygen containing functional groups, which otherwise prevents close enough contact for vdW bonding. Finally, the remaining CVD catalyst on the bottom of the CNT array is evaporated during annealing, enabling direct anchoring of the CNTs to the underlying graphite substrate.

    Download full text (pdf)
    Fulltext
  • 36. Hassel, M.
    et al.
    Svensson, Krister
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Andersson, S.
    Persson, M.
    Direct infrared photodesorption of physisorbed H_{2}1998In: Physical Review Letters, Vol. 80, no 11, article id 2481Article in journal (Refereed)
  • 37. Hassel, M.
    et al.
    Svensson, Krister
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Bellman, J.
    Andersson, S.
    Persson, M.
    Photodesorption of Physisorbed hydrogen molecules2002In: Physical Review B, Vol. 65, no 20, article id 205402Article in journal (Refereed)
  • 38.
    Hellman, Anders
    et al.
    Chalmers Tekniska Högskola.
    Svensson, Krister
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Andersson, Stig
    Göteborgs Universitet.
    Hydrogen-Induced Reconstruction of Cu(100): Two-Dimensional and One-Dimensional Structures of Surface Hydride2014In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 118, article id 15773Article in journal (Refereed)
    Abstract [en]

    Adsorption of atomic hydrogen has a remarkable influence on the structure and morphology of the Cu(100) surface. We have examined two specific situations; the well-known reconstructed p(2 × 2)-H surface and a one-dimensional (6 × 1)-H surface resembling the stripe reconstruction observed in an electrochemical environment. High resolution electron energy loss spectroscopy and density functional calculations show that the H atoms occupy only surface sites and that H bonding in induced 3-fold Cu surface hollow sites is a structural key element. The calculations support a transient scenario in which H absorption in subsurface sites is a critical intermediate step in the reconstruction of the Cu surface. We find clear evidence in terms of characteristic properties, like the H–Cu bond lengths and the dipole excited vibrational mode spectra, that these structures consist of two-dimensional and one-dimensional structures of surface hydride.

    Download full text (pdf)
    fulltext
  • 39.
    Jackman, Henrik
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Krakhmalev, Pavel
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Svensson, Krister
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Bending modulus of freestanding carbon nanotubes2010Conference paper (Other academic)
  • 40.
    Jackman, Henrik
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Krakhmalev, Pavel
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Enineering.
    Svensson, Krister
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Direct Measurements Of Bending Stiffness And Rippling Phenomena In Free-Standing Carbon Nanotubes2011Conference paper (Refereed)
  • 41.
    Jackman, Henrik
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Krakhmalev, Pavel
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Svensson, Krister
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    High resolution SEM imaging of carbon nanotubes: deconvolution and retrieval of intrinsic nanotube dimensions2012Conference paper (Refereed)
    Abstract [en]

    Characterizing physical properties of individual nanotubes is crucial for their implementation in nano electromechanical systems (NEMS). This requires measurements on suspended or free-standing structures together with accurate determination of the nanotubes dimensions. In situ methods are often used where physical measurements are performed inside electron microscopes [1-3]. Transmission electron microscopy (TEM) has the advantage of high resolution, providing accurate determination of both dimensions and the internal structure. The space inside a TEM is however rather restricted, leaving limited room for additional probes [4]. Scanning electron microscopy (SEM) on the other hand, has a large specimen chamber which facilitates the addition of probes, but the image resolution is lower, making the evaluation of material properties less accurate or even impossible for very thin nanotubes [1]. One way to solve this is to first measure the physical properties inside an SEM, and then determine the diameter using a TEM afterwards [1]. This approach requires transfer of the nanotube from the SEM to a suitable TEM sample holder, and analysis of the same sample-location in both instruments. It would thereby be advantageous to obtain accurate structural information directly inside the SEM [2]. We have studied the mechanisms involved in SEM image formation of small multiwalled nanotubes, 2-5 nm in diameter. The electron-probe shape in an SEM broadens the sample details, and the image can be seen as a convolution of the secondary electron yield at each sample position and the probe shape. By comparing SEM and TEM images, we found that the probe intensity profile was best described by a linear combination of Gaussian and Lorentzian distributions. Using the obtained probe shape, the SEM images could then be deconvoluted to reveal more details, including the inner diameter in some cases. We also show how the outer diameter can be obtained by differentiating image profiles, a method that does not require any detailed knowledge regarding the probe shape and is reliable down to dimensions comparable to the electron-probe size. This significantly improves the capabilities of in-situ SEM experiments by enabling accurate characterizations of nanofibres inside SEM instruments, without the need for subsequent TEM imaging

  • 42.
    Jackman, Henrik
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Krakhmalev, Pavel
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Svensson, Krister
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Image formation mechanisms in scanning electron microscopy of carbon nanotubes,and retrieval of their intrinsic dimensions.2013In: Ultramicroscopy, ISSN 0304-3991, Vol. 124, p. 35-39Article in journal (Refereed)
    Abstract [en]

    We present a detailed analysis of the image formation mechanisms that are involved in the imaging of carbon nanotubes with scanning electron microscopy (SEM). We show how SEM images can be modelled by accounting for surface enhancement effects together with the absorption coefficient for secondary electrons, and the electron-probe shape. Images can then be deconvoluted, enabling retrieval of the intrinsic nanotube dimensions. Accurate estimates of their dimensions can thereby be obtained even for structures that are comparable to the electron-probe size (on the order of 2 nm). We also present a simple and robust model for obtaining the outer diameter of nanotubes without any detailed knowledge about the electron-probe shape.

    Download full text (pdf)
    preprint_jackman
  • 43.
    Jackman, Henrik
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Krakhmalev, Pavel
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Svensson, Krister
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Large variations in the onset of rippling in concentric nanotubes.2014In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 104, article id 021910Article in journal (Refereed)
    Abstract [en]

    We present a detailed experimental study of the onset of rippling in highly crystalline carbon nanotubes. Modeling has shown that there should be a material constant, called the critical length, describing the dependence of the critical strain on the nanotube outer radius. Surprisingly, we have found very large variations, by a factor of three, in the critical length. We attribute this to a supporting effect from the inner walls in multiwalled concentric nanotubes. We provide an analytical expression for the maximum deflection prior to rippling, which is an important design consideration in nanoelectromechanical systems utilizing nanotubes.

    Download full text (pdf)
    APL 2014
  • 44.
    Jackman, Henrik
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Krakhmalev, Pavel
    Karlstad University, Faculty of Technology and Science.
    Svensson, Krister
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Measurements of the critical strain for rippling in carbon nanotubes2011In: Applied Physics Letters, ISSN 0003-6951, Vol. 98, no 18, p. 3 pages-Article in journal (Refereed)
    Abstract [en]

    We report measurements of the bending stiffness in free standing carbon nanotubes, using atomic force microscopy inside a scanning electron microscope. Two regimes with different bending stiffness were observed, indicative of a rippling deformation at high curvatures. The observed critical strains for rippling were in the order of a few percent and comparable to previous modeling predictions. We have also found indications that the presence of defects can give a higher critical strain value and a concomitant reduction in Youngs modulus.

    Download full text (pdf)
    fulltext
  • 45.
    Jackman, Henrik
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Krakhmalev, Pavel
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Svensson, Krister
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Mechanical behavior of carbon nanotubes in the rippled and buckled phase2015In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 117, no 8, p. 084318-Article in journal (Refereed)
    Abstract [en]

    We have studied the mechanical behavior of multi-walled carbon nanotubes for bending strains beyond the onset for rippling and buckling. We found a characteristic drop in the bending stiffness at the rippling and buckling onset and the relative retained stiffness was dependent on the nanotube dimensions and crystallinity. Thin tubes are more prone to buckle, where some lose all of their bending stiffness, while thicker tubes are more prone to ripple and on average retain about 20\% of their bending stiffness. In defect rich tubes the bending stiffness is very low prior to rippling but these tubes retain up to 70\% of their initial bending stiffness.

    Download full text (pdf)
    fulltext
  • 46.
    Jansson, Anna
    et al.
    Chalmers University of Technology.
    Nafari, Alexandra
    Chalmers University of Technology.
    Hedfalk, Kristina
    Göteborgs Universiet.
    Olsson, Eva
    Chalmers University of Technology.
    Svensson, Krister
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Sanz-Velasco, Anke
    Chalmers Tekniska Högskola.
    Monitoring the osmotic response of single yeast cells through force measurements in the environmental scanning electron microscope2014In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 25, article id 025901Article in journal (Refereed)
    Abstract [en]

    We present a measurement system that combines an environmental scanning electron microscope (ESEM) and an atomic force microscope (AFM). This combination enables studies of static and dynamic mechanical properties of hydrated specimens, such as individual living cells. The integrated AFM sensor provides direct and continuous force measurement based on piezoresistive force transduction, allowing the recording of events in the millisecond range. The in situ ESEM-AFM setup was used to study Pichia pastoris wild-type yeast cells. For the first time, a quantified measure of the osmotic response of an individual yeast cell inside an ESEM is presented. With this technique, cell size changes due to humidity variations can be monitored with nanometre accuracy. In addition, mechanical properties were extracted from load–displacement curves. A Young's modulus of 13–15 MPa was obtained for the Ppastoris yeast cells. The developed method is highly interesting as a complementary tool for the screening of drugs directed towards cellular water transport activity and provides new possibilities of studying mechanosensitive regulation of aquaporins.

  • 47.
    Jansson, Anna
    et al.
    Fysik, Chalmers Tekniska Högskola.
    Nafari, Alexandra
    Sanz-Velasco, Anke
    MC2, Chalmers Tekniska Högskola.
    Svensson, Krister
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Gustafsson, Stefan
    Fysik, Chalmers Tekniska Högskola.
    Hermansson, Ann-Marie
    Kemi, Chalmers Tekniska Högskola.
    Olsson, Eva
    Fysik, Chalmers Tekniska Högskola.
    Novel Method for Controlled Wetting of Materials in the Environmental Scanning Electron Microscope2013In: Microscopy and Microanalysis, ISSN 1431-9276, E-ISSN 1435-8115, Vol. 19, no 1, p. 30-7Article in journal (Refereed)
    Abstract [en]

    Environmental scanning electron microscopy has been extensively used for studying the wetting properties of different materials. For some types of investigation, however, the traditional ways of conducting in situ dynamic wetting experiments do not offer sufficient control over the wetting process. Here, we present a novel method for controlled wetting of materials in the environmental scanning electron microscope (ESEM). It offers improved control of the point of interaction between the water and the specimen and renders it more accessible for imaging. It also enables the study of water transport through a material by direct imaging. The method is based on the use of a piezo-driven nanomanipulator to bring a specimen in contact with a water reservoir in the ESEM chamber. The water reservoir is established by local condensation on a Peltier-cooled surface. A fixture was designed to make the experimental setup compatible with the standard Peltier cooling stage of the microscope. The developed technique was successfully applied to individual cellulose fibers, and the absorption and transport of water by individual cellulose fibers were imaged.

  • 48.
    Krakhmalev, Pavel
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Fredriksson, Gunnel
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Svensson, Krister
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Yadroitsev, Igor
    Bloemfontein Cent Univ Technol South Africa.
    Yadroitsava, Ina
    Bloemfontein Cent Univ Technol South Africa.
    Thuvander, M.
    Chalmers University.
    Peng, R.
    Linköping University.
    Microstructure, solidification texture, and thermal stability of 316 L stainless steel manufactured by laser powder bed fusion2018In: Metals, ISSN 2075-4701, Vol. 8, no 8, p. 1-18, article id 643Article in journal (Refereed)
    Abstract [en]

    This article overviews the scientific results of the microstructural features observed in 316 L stainless steel manufactured by the laser powder bed fusion (LPBF) method obtained by the authors, and discusses the results with respect to the recently published literature. Microscopic features of the LPBF microstructure, i.e., epitaxial nucleation, cellular structure, microsegregation, porosity, competitive colony growth, and solidification texture, were experimentally studied by scanning and transmission electron microscopy, diffraction methods, and atom probe tomography. The influence of laser power and laser scanning speed on the microstructure was discussed in the perspective of governing the microstructure by controlling the process parameters. It was shown that the three-dimensional (3D) zig-zag solidification texture observed in the LPBF 316 L was related to the laser scanning strategy. The thermal stability of the microstructure was investigated under isothermal annealing conditions. It was shown that the cells formed at solidification started to disappear at about 800 °C, and that this process leads to a substantial decrease in hardness. Colony boundaries, nevertheless, were quite stable, and no significant grain growth was observed after heat treatment at 1050 °C. The observed experimental results are discussed with respect to the fundamental knowledge of the solidification processes, and compared with the existing literature data.

    Download full text (pdf)
    Fulltext
  • 49. Krishnamurthy, S.
    et al.
    Montalti, M.
    Wardle, M.G.
    Shaw, M.J.
    Briddon, P.R.
    Svensson, Krister
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Hunt, M.R.C.
    Siller, L.
    Nitrogen ion irradiation of Au(110): Photoemission spectroscopy and possible crystal structures of gold nitride2004In: Physical Review BArticle in journal (Refereed)
  • 50.
    Kuzmenko, Volodymyr
    et al.
    Chalmers Tekniska Högskola.
    Saleem, Amin
    Chalmers Tekniska Högskola.
    Staaf, Henrik
    Chalmers Tekniska Högskola.
    Haque, Mazharul
    Chalmers Tekniska Högskola.
    Bhaskar, Arun
    Chalmers Tekniska Högskola.
    Flygare, Mattias
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Svensson, Krister
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Desmaris, Vincent
    Chalmers Tekniska Högskola.
    Enoksson, Peter
    Chalmers Tekniska Högskola.
    Hierarchical cellulose-derived CNF/CNT composites for electrostatic energy storage2016In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 26, no 12, article id 124001Article in journal (Refereed)
    Abstract [en]

    Today many applications require new effective approaches in energy delivery on demand. Supercapacitors are viewed as essential energy storage devices that can continuously provide quick energy. The performance of supercapacitors is mostly determined by electrode materials that can store energy via electrostatic charge accumulation. This study presents new sustainable cellulose-derived composite electrodes which consist of carbon nanofibrous (CNF) mats covered with vapor-grown carbon nanotubes (CNTs). The CNF/CNT electrodes have high electrical conductivity and surface area: two most important features that are responsible for good electrochemical performance of supercapacitor electrodes. The results show that the composite electrodes have fairly high values of specific capacitance, energy and power density and can retain excellent performance over at least 2 000 cycles. All of that makes us think that sustainable cellulose-derived composites can be extensively used in future as supercapacitor electrodes.

123 1 - 50 of 103
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • apa.csl
  • 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