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  • 251.
    Fuchs, Jürgen
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Wurtz, Albrecht
    On the geometry of coset branes2005In: Nuclear Physics B 724 (2005) 503-528Article in journal (Refereed)
    Abstract [en]

    Coset models and their symmetry preserving branes are studied from a representation theoretic perspective, relating e.g.

    the horizontal branching spaces to a truncation of

    the space of bulk fields, and accounting for

    field identification. This allows us to describe the fuzzy geometry of the branes at finite level.

  • 252.
    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.

  • 253.
    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

  • 254.
    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

  • 255.
    Gladh, Jörgen
    Karlstad University, Faculty of Technology and Science.
    Scanning Tunneling Microscopy and Low-Energy Electron Diffraction Studies of Quantum Wires on Si(332)2006Independent thesis Advanced level (degree of Magister), 20 points / 30 hpStudent thesis
    Abstract [en]

    In this master thesis I have investigated one-dimensional nanostructures, so called quantum wires. The goal was to grow them in situ on a stepped silicon surface and thereafter do several kinds of measurements, like Scanning Tunneling Microscopy, Low-Energy Electron Diffraction and Photoemission. The surface that was used was a Si(332) surface and the metals used in the growth of the quantum wires were gold and silver.

    After the preparation and measurement of the stepped surface, evaporation of silver and gold was performed. The Scanning Tunneling Spectroscopy measurments were done on both Ag/Si(332) and Au/Si(332) surfaces. This gave information about the local density of stats on the surfaces and possible bandgaps.

    All experiments were performed in ultra high vacuum, except the sample cutting and the first cleaning of the surface, which was done after the Shiraki method.

  • 256.
    Gladh, Jörgen
    Karlstad University, Division for Engineering Sciences, Physics and Mathematics.
    Tensor products, Fusion rules and su(2) Representations2008Independent thesis Advanced level (degree of Magister), 20 points / 30 hpStudent thesis
    Abstract [en]

    In this master thesis I have looked on two different kinds of representations of the Lie algebras su(2) and sl(2), and the tensor products of the representations.

    In the first case I looked at a tensor product involving a representation similar to one that appears in an article by A. van Tonder. This representation and tensor product was investigated mainly to get a good comprehension in the subject and to understand some of the problems that can arise.

    In the other case, which is the main problem in this thesis, I looked at a tensor product and representations that appears in an article by M. R. Gaberdiel. Here we deal with a tensor product of representations of su(2) with a specific value for the level at k = -4/3 and a specific eigenvalue of the Casimir operator at -2/9. This was done in the frame of finite dimensional Lie algebra and affine Lie algebra and not in the case of fusion rules as in the article by M. R. Gaberdiel.

    In both cases some of the calculations where done from in situ and the investigation of the representations behaviour due to the step operators, theirs eigenvalue and theirs weight system.

    Results and conclusions of the investigations are discussed in the last part of this thesis.

     

  • 257.
    Gregorcic, Bor
    et al.
    Uppsala University.
    Haglund, Jesper
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Conceptual Blending as an Interpretive Lens for Student Engagement with Technology: Exploring Celestial Motion on an Interactive Whiteboard2018In: Research in science education, ISSN 0157-244X, E-ISSN 1573-1898, p. 1-41Article in journal (Refereed)
    Abstract [en]

    We present and analyze video data of upper secondary school students’ engagement with a computer-supported collaborative learning environment that enables them to explore astronomical phenomena (Keplerian motion). The students’ activities have an immersive and exploratory character, as students engage in open-ended inquiry and interact physically with the virtual environment displayed on an interactive whiteboard. The interplay of students’ playful exploration through physical engagement with the simulation environment, their attention to physics concepts and laws, and knowledge about the real planets orbiting the Sun presents an analytical challenge for the researcher and instructor encountering such complex learning environments. We argue that the framework of conceptual blending is particularly apt for dealing with the learning environment at hand, because it allows us to take into account the many diverse mental inputs that seem to shape the student activities described in the paper. We show how conceptual blending can be brought together with theoretical ideas concerned with embodied cognition and epistemology of physics, in order to provide researchers and instructors with a powerful lens for looking critically at immersive technology-supported learning environments. 

  • 258. Grehk, T.M.
    et al.
    Götelidh, M.
    Karlsson, U.O.
    Johansson, Lars
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Gray, S.M.
    Magnusson, Kjell
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    The clean and Cs-exposed Si(111)3x3:B surface studied with photoemission1995In: Phys. Rev. B52, 11165 (1995)Article in journal (Refereed)
  • 259.
    Gunnarsson, Alva
    et al.
    Karlstad University, Faculty of Arts and Social Sciences (starting 2013), Department of Educational Studies (from 2013).
    Pohjonen, Emma
    Karlstad University, Faculty of Arts and Social Sciences (starting 2013), Department of Educational Studies (from 2013).
    - “Om det är damm på kommer det gå mycket fortare”.: En designbaserad studie om hur barn förklarar fenomenet luftmotstånd2019Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
  • 260. Gunnella, R.
    et al.
    Yeom, H. W.
    Bullock, E. L.
    Johansson, Lars
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Kono, S.
    Solal, F.
    Study of Si 2p core-level shift at the As/Si(001)-2×1 surface2002In: Surface Science 499, 244 (2002)Article in journal (Refereed)
    Abstract [en]

    The atomic origin of the photoemission Si 2p core level, shifted at 0.35 eV higher binding energy, at the As/Si(0 0 1)-2×1 surface, is investigated. The study is based on the determination of the surface structure by means of multiple scattering analysis of As 3d azimuth photoelectron diffraction (PD) patterns. The obtained structure is used to assign the atomic origin of the Si 2p component by surface core level shift PD. We find that a single atom contributes to the core level, while, on the basis of final state calculations, a contribution from two different atoms would be expected

  • 261. Gurnett, Michael
    Photoemission and Theoretical Studies of the Alkali Metal and Ag-Induced 3x1 and (square root of 3) x (square root of 3) Reconstructions on Si(111) and Ge(111)2005Doctoral thesis, monograph (Other academic)
  • 262. Gurnett, Michael
    Photoemission Studies of the M/Si(111)-3x1 Reconstructions for M=Li, Na, K, and Ag2003Licentiate thesis, monograph (Other academic)
    Abstract [en]

    The work reported here relates to a class of reconstructions on the Si(111) surface with 3?1 or 6?1 periodicity that are believed to be similar for Ag, Mg and the alkali metals (Li, K, and Na). The electronic structure of this reconstruction was studied by means of angle-resolved photoelectron spectroscopy of the valence bands of the Ag/Si(111)-3?1/6?1 reconstruction. Theoretical valence band maps calculated using Density Functional Theory (DFT) were found to agree well with the experimentally obtained valence band maps for the Ag/Si(111)-3?1/6?1 reconstruction. The geometric structure and bonding was investigated by core-level spectroscopy of the M/Si(111)-3?1 surfaces for M=Li, K, and Na, as well as the Ag/Si(111)-3?1/6?1 and Ag/Si(111)-c(12?2) reconstructions.

  • 263. Gurnett, Michael
    et al.
    Gustafsson, Jörgen
    Holleboom, Thijs Jan
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Magnusson, Kjell
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Widstrand, Susanna
    Johansson, Lars
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Johansson, M.K.-J.
    Gray, S.M.
    Core-level spectroscopy study of the Li/Si(111)-3x1, Na/Si(111)-3x1 and K/Si(111)-3x1 surfaces2005In: Phys. Rev. B 71, 195408 (2005)Article in journal (Refereed)
  • 264. Gurnett, Michael
    et al.
    Gustafsson, Jörgen
    Magnusson, Kjell
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Widstrand, Susanna
    Johansson, Lars
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Angle-resolved photoemission study of the single-domain Si(111) 3×1/6×1 -Ag surface2002In: Phys. Rev. B 66, 161101 (R) (2002)Article in journal (Refereed)
  • 265.
    Gurnett, Michael
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Holleboom, Thijs
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Zhang, Hanmin
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Johansson, Lars
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Photoemission study of the Li/Ge(111)-3×1 reconstruction2009In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, ISSN 0039-6028, Vol. 603, no 4, p. 727-735Article in journal (Refereed)
    Abstract [en]

    In this article we report our findings on the electronic structure of the Li induced Ge(1 1 1)–3 × 1reconstruction as determined by angle-resolved ultraviolet photoelectron spectroscopy (ARUPS) and core-level spectroscopy using synchrotron radiation. The results are compared to the theoretical honeycomb-chain-channel (HCC) model for the 3 × 1reconstruction as calculated using density functional theory (DFT). ARUPS measurements were performed in both the and directions of the 1 × 1 surface Brillouin zone at photon energies of 17 and 21.2 eV. Three surface related states were observed in the direction. In the direction, at least two surface states were seen. The calculated band structure using the single-domain HCC model for Li/Ge(1 1 1)–3 × 1 was in good agreement with experiment, allowing for the determination of the origin of the experimentally observed surface states. In the Ge core-level spectra, two surface related components were identified, both at lower binding energy with respect to the Ge bulk peak. Our DFT calculations of the surface core-level shifts were found to be in fair agreement with the experimental results. Finally, in contrast to the Li/Si(1 1 1)–3 × 1 case, no double bond between Ge atoms in the top layer was found

  • 266. Gustafsson, Jörgen
    Electron spectroscopy and scanning tunnelling microscopy studies of PTCDA on well-ordered semiconductor surfaces2005Doctoral thesis, monograph (Other academic)
  • 267. Gustafsson, Jörgen
    Growth and characterization of thin PTCDA films on Si(001)2004Licentiate thesis, monograph (Other academic)
    Abstract [en]

    The research presented in this thesis concerns experimental studies of the large aromatic semiconducting molecule 3,4,9,10 perylenetetracarboxylic dianhydride (PTCDA) on a clean and hydrogen passivated Si(001) substrate. Thin organic films have the potential use in various electronic and optical devices. The PTCDA/Si(001) is a model system for an organic/inorganic homo junction. The growth and electronic structure of thin PTCDA films was studied in situ at various film thickness ranging from sub-monolayer up to 10 monolayer thickness. The experimental methods used were photoelectron spectroscopy, X-ray absorption

    spectroscopy and atomic force microscopy. On the passivated surface the film grows with flat lying molecules. At a coverage about 0.5-2 ML the growth mode changes from a layer by layer to a Stranski-Krastanov growth mode for thicker films. The interaction between the substrate is weak and the electronic structure of the film have only a very small dependence of the film thickness. On the clean surface the substrate-molecule interaction is strong. This give a Stranski-Krastanov growth mode with a change in the molecular orientation, the island size

    and shape as well as the electronic structure of the film.

  • 268. Gustafsson, Jörgen
    et al.
    Moons, E.
    Widstrand, S.M.
    Johansson, L.S.O.
    Growth and characterization of thin PTCDA films on 3C-SiC(0 0 1)c(2 × 2)2006In: Surface Science, 600 (2006) p. 4758Article in journal (Refereed)
  • 269. Gustafsson, Jörgen
    et al.
    Moons, Ellen
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Widstrand, Susanna
    Gurnett, Michael
    Johansson, Lars
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Thin PTCDA Films on Si(001) II: Electronic Structure2004In: Surface Science 572, 32 (2004)Article in journal (Refereed)
    Abstract [en]

    We have studied the thin film formation and the electronic structure of the organic molecular semiconductor 3,4,9,10 perylene tetracarboxylic dianhydride (PTCDA), on clean and on hydrogen-passivated Si(0 0 1) surfaces. The studies were made by means of high resolution X-ray photoelectron spectroscopy (HRXPS), angle-resolved photoelectron spectroscopy (ARPES), near edge X-ray absorption fine structure (NEXAFS) and low energy electron diffraction (LEED). On the H passivated surface the changes in the electronic structure of the substrate and the molecules with increasing film thickness are very small. The molecular orbitals show a dispersive behavior, indicating that the PTCDA layers are ordered. On the reactive clean surface the anhydride groups of the molecule interact with the substrate as indicated by changes in the core level binding energies. This results in a much lower ordering in the film compared to PTCDA on a passivated silicon surface. There is no sign of decomposition of the molecule because of the more reactive substrate

  • 270. Gustafsson, Jörgen
    et al.
    Moons, Ellen
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Widstrand, Susanna
    Johansson, Lars
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Thin PTCDA Films on Si(001) I: Growth Mode2004In: Surface Science 572, 23 (2004)Article in journal (Refereed)
    Abstract [en]

    We have studied the interface and thin film formation of the organic molecular semiconductor 3,4,9,10 perylene tetracarboxylic dianhydride (PTCDA) on clean and on hydrogen passivated Si(0 0 1) surfaces. The studies were made by means of high resolution X-ray photoelectron spectroscopy (HRXPS), near edge X-ray absorption fine structure (NEXAFS), low energy electron diffraction (LEED), and atomic force microscopy (AFM). On the passivated surface the LEED pattern is somewhat diffuse but reveals that the molecules grow in several ordered domains with equivalent orientations to the substrate. NEXAFS shows that the molecules are lying flat on the substrate. The Si 2p XPS line shape is not affected when the film is deposited so it can be concluded that the interaction at the interface between PTCDA and the substrate is weak. The evolution of the film formation appears to be homogeneous for the first monolayer with a nearly complete coverage of flat lying molecules based on the XPS attenuation. For layer thickness of 0.52 monolayers (ML) the molecules start to form islands, attracting the molecules in between, leaving the substrate partly uncovered. For thicker films there is a StranskiKrastanov growth mode with thick islands and a monolayer thick film in between. For the clean surface the ordering of the film is much lower and angle resolved photoelectron spectroscopy (ARPES) of the molecular orbitals have only a small dependence of the emission angle. NEXAFS shows that the molecules do not lie flat on the surface and also reveal a chemical interaction at the interface

  • 271. Gustafsson, Jörgen
    et al.
    Widstrand, Susanna
    Moons, Ellen
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Johansson, Lars
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Growth and characterization of thin PTCDA films on 3C-SiC(001)c(2x2)2006Article in journal (Refereed)
  • 272. Gustafsson, Jörgen
    et al.
    Zhang, H. M.
    Johansson, L. S.
    STM studies of thin PTCDA films on AgSi(111)-sqrt[3] ×sqrt[3]2007In: Phys. Rev. B 75, 155414 (2007)Article in journal (Refereed)
  • 273. Gustafsson, Jörgen
    et al.
    Zhang, H. M.
    Moons, E.
    Johansson, L. S.
    Electron spectroscopy studies of PTCDA on AgSi(111)-sqrt[3] ×sqrt[3]2007In: Phys. Rev. B 75, 155413 (2007)Article in journal (Refereed)
  • 274.
    Gustafsson, Jörgen
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Zhang, Hanmin
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Johansson, Lars
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    STM studies of thin PTCDA films on Ag/Si(111) )-sqrt3×sqrt32007In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 75, p. 155414-1-155414-7Article in journal (Refereed)
  • 275. Gustafsson, Jörgen
    et al.
    Zhang, Hanmin
    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.
    Johansson, Lars
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Electron spectroscopy studies of PTCDA on Ag/Si(111) )- √3 × √32007In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 75, no 15, p. 155413-Article in journal (Refereed)
  • 276.
    Gustafsson, Marcus
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Thermal Contributions and Balances in Flatness Measuring Roll: Modelling of Thermal Balances and Convective Heat Transfer Using CFD2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Devices for measurement of flatness in rolling mills is important to ensure high quality products and fewer strip breaks. One of these devices take the form of a measuring roll, which the strip is guided over after it has exited the reduction stage in the mill. The roll is traditionally used in cold rolling applications, and a desire to move to hot rolling introduces demands for research into the thermal balances that develops under operation. This report aims to create an overview into some of the contributions that make up the thermal balance, namely external convection and friction losses in bearings. Other contributions have been investigated by C. Karlsson (Master of Science thesis, Karlstad University, 2018). The heat transfer coefficients obtained for external convection proved to be too small to sustain reasonable temperatures under operation, if no type of cooling apparatus is utilized. Even with external cooling using pressurized air, the convective heat dissipation is too low, due to efficient strip-to-roll conduction. From the modelling performed in this report, friction losses from bearings can be considered as negligible. A model for describing the thermal balances using Newton’s law of cooling was developed, and related to steady state operating conditions by the use of a correction factor. The factor was obtained by comparing the cooling law with the results of a more precise numerical model. The studies in this project elucidate the critical aspects of the thermal balances and provides a basis for further, more detailed modelling.

  • 277.
    Gustafsson, Oscar
    et al.
    KT.
    Karim, Amir
    Acreo AB, Sweden.
    Berggren, Jesper
    KTH.
    Wang, Qin
    Acreo AB, Sweden.
    Reuterskiöld-Hedlund, Carl
    KTH.
    Ernerheim-Jokumsen, Christopher
    KTH.
    Soldemo, Markus
    KTH.
    Weissenrieder, Jonas
    KTH.
    Persson, Sirpa
    Acreo AB, Sweden.
    Almqvist, Susanne
    Acreo AB, Sweden.
    Ekenberg, Ulf
    KTH.
    Noharet, Bertrand
    Asplund, Carl
    IRnova AB, Sweden.
    Göthelid, Mats
    KTH.
    Andersson, Jan Y.
    Acreo AB, Sweden.
    Hammar, Mattias
    KTH.
    Photoluminescence and photoresponse from InSb/InAs-based quantum dot structures2012In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 20, no 19, p. 21264-21271Article in journal (Refereed)
    Abstract [en]

    InSb-based quantum dots grown by metal-organic vapor-phase epitaxy (MOVPE) on InAs substrates are studied for use as the active material in interband photon detectors. Long-wavelength infrared (LWIR) photoluminescence is demonstrated with peak emission at 8.5 mu m and photoresponse, interpreted to originate from type-II interband transitions in a p-i-n photodiode, was measured up to 6 mu m, both at 80 K. The possibilities and benefits of operation in the LWIR range (8-12 mu m) are discussed and the results suggest that InSb-based quantum dot structures can be suitable candidates for photon detection in the LWIR regime.

  • 278.
    Gustavsson, Anders
    Karlstad University, Division for Engineering Sciences, Physics and Mathematics.
    Klimatsimulering av ett kontorsrum: Hur de termiska stigkrafterna påverkar ventilationseffektiviteten2006Independent thesis Basic level (professional degree), 10 points / 15 hpStudent thesis
    Abstract [en]

    Abstract

    In urban societies people spend more and more time indoors, which put great demands on the indoor environment. If the ventilation is to manage the removal of unwanted substances in the indoor air, a good mixing of the air is required. The question arises that, whether the buoyancy forces will counteract a good mixing of the indoor air or not?

    This report aims to clear up the difficulties whether you need to consider the buoyancy forces or not, when adjusting a ventilation unit. For studying the indoor mixing of the air a two dimensional model is constructed in COMSOL Multiphysics. In this model several supply air temperatures is simulated to see how much the temperature affects the mixing of the air.

    The physical relations that are being used in this model is the Navier-Stoke’s equation for Non-Isothermal flow, the relations for General Heat transfer and the relation for Convection and Diffusion. These relations exist as tools in COMSOL Multiphysics.

    It wasn’t possible to get the model to converge at low air velocities, because the model is dependent of accuracy in the field of cm or mm.

    The lowest velocity, in the zone of occupancy, which the model was able to simulate was 0.5 m/s but it takes velocities below 0.2 m/s to fulfill the indoor climate requirements due to the problems concerning draft.

    It was possible to see that the buoyancy forces affect the mixing of the air to a certain degree, despite high air velocities.

    Unfortunately it wasn’t possible to see to what degree you have to consider the buoyancy forces when adjusting a ventilation unit. To see the affects of the buoyancy forces or not, is highly dependent on the velocity of the air. Because the force generated by the supply air increases by the square of the velocity change.

    When constructing a more detailed model, which is a requirement for convergence when having low velocities, the memory of the computer isn’t enough.

    The results of the simulations show that a computer with more calculation capacity, than the Karlstad University can offer, is needed to make a successful simulation.

  • 279.
    Haarahiltunen, Antti
    et al.
    Aalto University.
    Yli-Koski, Marko
    Aalto University.
    Talvitie, Heli
    Aalto University.
    Vähänissi, Ville
    Aalto University.
    Lindroos, Jeanette
    Aalto Universitet, Dept Micro & Nanoscience.
    Savin, Hele
    Aalto University.
    Gettering of iron in CZ-silicon by polysilicon layer2011In: Physica Status Solidi. C, Current topics in solid state physics, ISSN 1610-1634, E-ISSN 1610-1642, Vol. 8, no 3, p. 751-754Article in journal (Refereed)
  • 280. Hahn, Giso
    et al.
    Zechner, C.
    Rinio, Markus
    Fath, Peter
    Willeke, G.
    Bucher, E.
    Enhanced Carrier Collection observed in Mechanically Structured Silicon with Small Diffusion Length1999In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 86, no 12, p. 43-47 mflArticle in journal (Refereed)
    Abstract [en]

    The diffusion length of minority charge carriers in the silicon bulk Ldiffis an important characteristicof optoelectronic devices fabricated from low cost silicon wafers. In this study computer simulationshave been carried out to calculate the beneficial effects of a macroscopic surface texturization on thecharge carrier generation and the collection probability. Textured solar cells should be able tocollect charge carriers more effectively resulting in an increased current due to the special emittergeometry resulting from the texture, decreased reflection losses, and the inclined penetration of thelight. In order to prove this expected behavior, deeply V-textured solar cells have been processedand characterized on low cost silicon reaching an Ldiffof about 25 mm. Spatially resolved highresolution measurements of the internal quantum efficiency exhibit a strongly increased signal in thetexture tips which is the first experimental proof of the increased charge carrier collectionprobability of deeply textured solar cells. This effect can further be seen in cross sectional electronbeam induced current measurements and the mechanical texture results in an overall gain in shortcircuit current density of about 11% and in efficiency of about 8% relatively.

  • 281. Haider, Miran
    Geometric Phases In Quantum Systems Of Pure And Mixed State2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Note that equations and expressions has been omitted here and is instead presented in the work. 

    This thesis focuses on the geometric phase in pure and mixed quantum states. For the case of a pure quantum state, Berry's adiabatic approach (4.1.10) and Aharonov & Anandan's non-adiabatic generalization of Berry's approach (4.2.8) are included in this work. Mixed quantum state involves Uhlmanns approach (5.1.42), which is used extensively in Section 7 and Sjöqvist's et al. approach (5.2.22), used extensively in Section 6. Sjöqvist's approach states that the Uhlmann phase is an observable and provides the experimental groundworkusing an interferometer.􀀀This was later proven, by Du et al.[45] to reproduce experimental data (Figure 19) on page 56.

    The Uhlmann phase can be used to observe the behaviour of topological kinks. This was tested on 3 models, the Creutz-ladder, the Majorana chain andthe SSU-model. It is found that the Uhlmann phase is split into two regimes with the dividing parameter being the temperature. This temperature is called the critical temperature, Tc. If the temperatureis is below the critical temperature, the Uhlmann phase yields Π and if thetemperature is above the critical temperature, the Uhlmann phase yields zero.

  • 282.
    Hansson, Rickard
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Materials and Device Engineering for Efficient and Stable Polymer Solar Cells2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Polymer solar cells form a promising technology for converting sunlight into electricity, and have reached record efficiencies over 10% and lifetimes of several years. The performance of polymer solar cells depends strongly on the distribution of electron donor and acceptor materials in the active layer. To achieve longer lifetimes, degradation processes in the materials have to be understood. In this thesis, a set of complementary spectroscopy and microscopy techniques, among which soft X-ray techniques have been used to determine the morphology of polymer:fullerene based active layers. We have found that the morphology of TQ1:PC70BM films is strongly influenced by the processing solvent and the use of solvent additives. We have also found, by using soft X-ray techniques, that not only the light-absorbing polymer TQ1, but also the fullerene is susceptible to photo-degradation in air. Moreover, the fullerene degradation is accelerated in the presence of the polymer. Additionally, this thesis addresses the role of the interfacial layers for device performance and stability. The commonly used hole transport material PEDOT:PSS has the advantage of being solution processable at room temperature, but this layer is also known to contribute to the device degradation. We have found that low-temperature processed NiOx is a promising alternative to PEDOT:PSS, leading to improved device performance. Even for encapsulated polymer solar cells, some photo-induced degradation of the electrical performance is observed and is found to depend on the nature of the hole transport material. We found a better initial stability for solar cells with MoO3 hole transport layers than with PEDOT:PSS. In the pursuit of understanding the initial decrease in electrical performance of PEDOT:PSS-based devices, simulations were performed, from which a number of degradation sources could be excluded.

  • 283.
    Hansson, Rickard
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Morphology and material stability in polymer solar cells2015Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Polymer solar cells are promising in that they are inexpensive to produce, and due to their mechanical flexibility have the potential for use in applications not possible for more traditional types of solar cells. The performance of polymer solar cells depends strongly on the distribution of electron donor and acceptor material in the active layer. Understanding the connection between morphology and performance as well as how to control the morphology, is therefore of great importance. Furthermore, improving the lifetime of polymer solar cells has become at least as important as improving the efficiency.

     

    In this thesis, the relation between morphology and solar cell performance is studied, and the material stability for blend films of the thiophene-quinoxaline copolymer TQ1 and the fullerene derivatives PCBM and PC70BM. Atomic force microscopy (AFM) and scanning transmission X-ray microscopy (STXM) are used to investigate the lateral morphology, secondary ion mass spectrometry (SIMS) to measure the vertical morphology and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy to determine the surface composition. Lateral phase-separated domains are observed whose size is correlated to the solar cell performance, while the observed TQ1 surface enrichment does not affect the performance. Changes to the unoccupied molecular orbitals as a result of illumination in ambient air are observed by NEXAFS spectroscopy for PCBM, but not for TQ1. The NEXAFS spectrum of PCBM in a blend with TQ1 changes more than that of pristine PCBM. Solar cells in which the active layer has been illuminated in air prior to the deposition of the top electrode exhibit greatly reduced electrical performance. The valence band and absorption spectrum of TQ1 is affected by illumination in air, but the effects are not large enough to account for losses in solar cell performance, which are mainly attributed to PCBM degradation at the active layer surface.

  • 284. Hansson, Rickard
    NiO nanoparticles in P3HT:PCBM Bulk Heterojunction Solar Cells2011Independent thesis Advanced level (degree of Master (Two Years)), 30 credits / 45 HE creditsStudent thesis
    Abstract [en]

    With the amount of energy reaching the earth as sunlight being so large that only a small fraction would be enough to satisfy the world’s energy consumption, solar cells have the potential of playing an important role in the electricity generation of the future. The high production costs of the currently commercial silicon-based solar cells have stimulated the development of alternative solar cells. Among these, polymer solar cells with their low fabrication cost, mechanical flexibility and light weight are particularly promising. One problem with polymer solar cells is their short life time. To prevent electron leakage from the active layer to the ITO anode, a thin layer of PEDOT:PSS is often deposited between the active layer and the anode to serve as a hole transporting layer (HTL). The problem is that PEDOT:PSS is acidic and can degrade the ITO and thereby reduce the lifetime of the polymer solar cell. P-type NiO, with its high band gap and low electron affinity, is a promising alternative for PEDOT:PSS.

    In this thesis work, polymer solar cells are fabricated in which NiO nanoparticles are deposited onto the ITO surface by spincoating as HTL. For comparison, polymer solar cells with PEDOT:PSS as HTL are fabricated. Polymer solar cells with NiO nanoparticles dispersed inside the active layer are also fabricated.

    AFM is used to see how the ITO surface structure is affected when spincoated with the NiO nanoparticles. The NiO nanoparticles are characterized by SEM, TEM, XPS, absorption spectroscopy and their work function is measured by a Kelvin Probe.

    The solar cells with NiO as HTL worked but did not perform as well as the solar cells with PEDOT:PSS as HTL. AFM studies showed that after spincoating with the NiO nanoparticles, the ITO surface is covered and as smooth as when covered with PEDOT:PSS. The solar cells with NiO nanoparticles dispersed in the active layer displayed similar performance as solar cells without NiO with the exception of one device showing a 30% increase in short circuit current density. However, the solar cells with PEDOT:PSS as HTL displayed a rather large variation in performance so more devices would have to be fabricated to really know if the added NiO was the reason for the increase in JSC. The NiO nanoparticles have a size of 50-100 nm and are polycrystalline. The band gap was determined to be 3.6 eV and the work function 5.0 eV.

  • 285.
    Hansson, Rickard
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Ericsson, Leif
    Karlstad University, Faculty of Technology and Science, Materials Science. Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Holmes, Natalie P.
    Blazinic, Vanja
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Dastoor, Paul
    Moons, Ellen
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Opportunities and challenges in probing local composition of organic material blends for photovoltaics2017In: Journal of Materials Research, ISSN 0884-2914, E-ISSN 2044-5326, Vol. 32, no 10, p. 1982-1992Article in journal (Refereed)
  • 286.
    Hansson, Rickard
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Ericsson, Leif K.E.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Holmes, Natalie P.
    Centre for Organic Electronics, University of Newcastle, Callaghan, NSW 2308, Australia.
    Rysz, Jakub
    M. Smoluchowski Insitute of Physics, Jagiellonian University, Reymonta 4, Krakow 30–059, Poland.
    Opitz, Andreas
    Department of Physics, Humboldt-Universit¨at zu Berlin, 12489 Berlin, Germany.
    Campoy-Quiles, Mariano
    Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus UAB, Bellaterra, 08193, Spain.
    Wang, Ergang
    Chalmers University of Technology, 41296 Göteborg, Sweden.
    Barr, Matthew G.
    Centre for Organic Electronics, University of Newcastle, Callaghan, NSW 2308, Australia.
    Kilcoyne, A. L. David
    Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
    Zhou, Xiaojing
    Centre for Organic Electronics, University of Newcastle, Callaghan, NSW 2308, Australia.
    Dastoor, Paul
    Centre for Organic Electronics, University of Newcastle, Callaghan, NSW 2308, Australia.
    Moons, Ellen
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Vertical and lateral morphology effects on solar cell performance for a thiophene–quinoxaline copolymer:PC70BM blend2015In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 3, p. 6970-6979Article in journal (Refereed)
  • 287.
    Hansson, Rickard
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Lindqvist, Camilla
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Ericsson, Leif
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Opitz, Andreas
    Humboldt univ. .
    Wang, Ergang
    Chalmers.
    Moons, Ellen
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Photodegradation in air of the active layer components in a thiophene-quinoxaline copolymer:fullerene solar cell2016In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 18, no 16, p. 11132-11138Article in journal (Refereed)
    Abstract [en]

    We have studied the photo-degradation in air of a blend of [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) and poly[2,3-bis-(3-octyloxyphenyl)quinoxaline-5,8-diyl-alt-thiophene-2,5-diyl] (TQ1), and how the photo-degradation affects the solar cell performance. Using near-edge X-ray absorption fine structure (NEXAFS) spectroscopy, changes to the electronic structure of TQ1 and PCBM caused by illumination in ambient air are investigated and compared between the pristine materials and the blend. The NEXAFS spectra show that the unoccupied molecular orbitals of TQ1 are not significantly changed by the exposure of pristine TQ1 to light in air, whereas those of PCBM are severely affected as a result of photo-induced degradation of PCBM. Furthermore, the photo-degradation of PCBM is accelerated by blending it with TQ1. While the NEXAFS spectrum of TQ1 remains unchanged upon illumination in air, its valence band spectrum shows that the occupied molecular orbitals are weakly affected. Yet, UV-Vis absorption spectra demonstrate photo-bleaching of TQ1, which is attenuated in the presence of PCBM in blend films. Illumination of the active layer of TQ1: PCBM solar cells prior to cathode deposition causes severe losses in electrical performance.

  • 288. 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)
  • 289. 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)
  • 290.
    Heidkamp, Hannah
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Carlsson, Gunilla
    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.
    van Stam, Jan
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Polymer film formation studied with fluorescence microscopy and AFM2010In: Molecular Processes at Solid Surfaces: 10th Annual Surface and Colloid Symposium, 2010, p. 49-Conference paper (Refereed)
    Abstract [en]

    Thin polymer films are used in many applications such as paint, paper coatings and electronic devices. For these applications, it is important to have knowledge about the film formation process, since it affect the film morphology and the morphology is important for the applications.One method for studying film formation in situ is fluorescence microscopy. By labeling a target molecule or particle with a fluorophore, the targets movements can be traced as the solvent evaporates [1-3]. If information gained from studies of particle movements during film formation and wet state behavior are combined, information about the film formation process can be obtained. Examination of the final film surfaces with regular light microscopy and AFM gives additional information about the film formation.These methods have been used for studying the formation of negatively charged latex films. It was shown that the films are greatly affected by adding positively charged surfactants [4-5]. Since latex is a water-based system it has relatively long drying times. Systems based on high-vapor pressure organic solvents have much shorter drying times and the film formation occurs under non-equilibrium conditions. This results in incomplete phase separation, which in turn gives microstructures in the film. These microstructures are of great interest since they affect the properties of the film and its function [6-7]. Our aim is to develop the methods used for latex studies in order to be able to apply them to study film formation of polymer blends used for photovoltaic applications. The goal is to get more knowledge about the film forming process and a deeper understanding about the mechanisms behind the formation of microstructures.[1] Carlsson G., Warszynski P., van Stam J., J. Colloid Interface Sci., 2003, 267, 500-508[2] Carlsson G., van Stam J., Nord. Pulp Pap. Res. J., 2005, 20, 192-199[3] Carlsson G., Järnström L., van Stam J., J. Colloid Interface Sci., 2006, 298, 162-171[4] Heidkamp H., Master thesis, Karlstad University 2009.[5] Paakkonen, J., Master thesis, Karlstad University 2010.[6] Björström C.M., Magnusson K.O., Moons E., Synth. Metals, 2005, 152, 109-112[7] Moons E., J. Phys.: Condens. Matter, 2002, 14, 12235-12260

  • 291.
    Heidkamp, Hannah
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    van Stam, Jan
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Carlsson, Gunilla
    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.
    Dzwilewski, Andrzej
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Rogowski, Rafal
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Morphology of P3HT and PCBM blends in thin films obtained with different deposition methods2011Conference paper (Refereed)
    Abstract [en]

    Patterns and structures, formed when a semiconducting polymer blend in solution is subject to controlled evaporation, have been of great interest due to their influence on the performance of organic devices. By controlling the processes of pattern formation, function properties of organic semiconductor structures can be tailored, allowing for facile manufacturing of the active layers in organic devices, e.g. solar cells.

    By analyzing the morphologies of polymer blends resulting from different deposition methods, a deeper insight into the pattern formation process can be acquired. In this study, we have analyzed the morphology of blends of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) formed upon solvent evaporation. We used the following deposition methods: dip-coating, droplet evaporation within a constrained geometry and drop-casting. Dip-coated films revealed various types of morphology depending on the coating speed. At low coating speeds, where evaporation is the dominant factor, well-ordered patterns were obtained. When increasing the coating speed, viscous forces become dominant over evaporation yielding optically homogenous films [2]. Morphologically similar structures to those observed at low coating speeds, were also obtained with spatially constrained droplets. The blend morphologies were analyzed with polarized, fluorescence and atomic force microscopy [1].

    References:

    [1] C. M. Björström Svanström, J. Rysz, A. Bernasik, A. Budkowski, F. Zhang, O. Inganäs, M. R. Andersson, K. O. Magnusson, J. J. Benson-Smith, J. Nelson, and E. Moons, Adv. Mat. 21, 4398-4403 (2009)

    [2] R. Z. Rogowski and A. A. Darhuber, Langmuir 26, 11485-93 (2010)

  • 292. Heinzle, J. Mark
    et al.
    Uggla, Claes
    Karlstad University, Faculty of Technology and Science.
    A new proof of the Bianchi type IX attractor theorem2009In: Classical and quantum gravity, ISSN 0264-9381, E-ISSN 1361-6382, Vol. 26, no 7, p. 1-28Article in journal (Refereed)
    Abstract [en]

    We consider the dynamics towards the initial singularity of Bianchi type IX vacuum and orthogonal perfect fluid models with a linear equation of state. The `Bianchi type IX attractor theorem' states that the past asymptotic behavior of generic type IX solutions is governed by Bianchi type I and II vacuum states (Mixmaster attractor). We give a comparatively short and self-contained new proof of this theorem. The proof we give is interesting in itself, but more importantly it illustrates and emphasizes that type IX is special, and to some extent misleading when one considers the broader context of generic models without symmetries

  • 293. Heinzle, J. Mark
    et al.
    Uggla, Claes
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Mixmaster: Fact and Belief2009In: Classical and quantum gravity, ISSN 0264-9381, E-ISSN 1361-6382, Vol. 26, no 075016, p. 1-34Article in journal (Refereed)
    Abstract [en]

    We consider the dynamics towards the initial singularity of Bianchi type IX vacuum and orthogonal perfect fluid models with a linear equation of state. Surprisingly few facts are known about the `Mixmaster' dynamics of these models, while at the same time most of the commonly held beliefs are rather vague. In this paper, we use Mixmaster facts as a base to build an infrastructure that makes it possible to sharpen the main Mixmaster beliefs. We formulate explicit conjectures concerning (i) the past asymptotic states of type IX solutions and (ii) the relevance of the Mixmaster/Kasner map for generic past asymptotic dynamics. The evidence for the conjectures is based on a study of the stochastic properties of this map in conjunction with dynamical systems techniques. We use a dynamical systems formulation, since this approach has so far been the only successful path to obtain theorems, but we also make comparisons with the `metric' and Hamiltonian `billiard' approaches

  • 294. Heinzle, J Mark
    et al.
    Uggla, Claes
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Monotonic functions in Bianchi models: why they exist and how to find them2010In: Classical and quantum gravity, ISSN 0264-9381, E-ISSN 1361-6382, Vol. 27, no 1Article in journal (Refereed)
    Abstract [en]

    All rigorous and detailed dynamical results in Bianchi cosmology rest upon the existence of a hierarchical structure of conserved quantities and monotonic functions. In this paper we uncover the underlying general mechanism and derive this hierarchical structure from the scale-automorphism group for an illustrative example, vacuum and diagonal class A perfect fluid models. First, kinematically, the scale-automorphism group leads to a reduced dynamical system that consists of a hierarchy of scale-automorphism invariant sets. Second, we show that, dynamically, the scale-automorphism group results in scale-automorphism invariant monotone functions and conserved quantities that restrict the flow of the reduced dynamical system

  • 295.
    Heinzle, Mark
    et al.
    University of Vienna, Faculty of Physics, Gravitational Physics, Austria.
    Sandin, Patrik
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    The Initial Singularity of Ultrastiff Perfect Fluid Spacetimes Without Symmetries2012In: Communications in Mathematical Physics, ISSN 0010-3616, E-ISSN 1432-0916, no 313, p. 385-403Article in journal (Refereed)
    Abstract [en]

    We consider the Einstein equations coupled to an ultrastiff perfect fluid and prove the existence of a family of solutions with an initial singularity whose structure is that of explicit isotropic models. This family of solutions is ‘generic’ in the sense that it depends on as many free functions as a general solution, i.e., without imposing any symmetry assumptions, of the Einstein-Euler equations. The method we use is a that of a Fuchsian reduction.

  • 296.
    Heinzle, Mark
    et al.
    University of Vienna, Austria.
    Uggla, Claes
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Spike Statistics2013In: General Relativity and Gravitation, ISSN 0001-7701, E-ISSN 1572-9532, Vol. 45, no 5, p. 939-957Article in journal (Refereed)
    Abstract [en]

    In this paper we explore stochastical and statistical properties of so-called recurring spike induced Kasner sequences. Such sequences arise in recurring spike formation, which is needed together with the more familiar BKL scenario to yield a complete description of generic spacelike singularities. In particular we derive a probability distribution for recurring spike induced Kasner sequences, complementing similar available BKL results, which makes comparisons possible. As examples of applications, we derive results for so-called large and small curvature phases and the Hubble-normalized Weyl scalar.

  • 297.
    Heinzle, Mark
    et al.
    University of Vienna, Austria.
    Uggla, Claes
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Lim, Woei Chet
    University of Waikato, New Zealand.
    Spike oscillations2012In: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 86, p. 104049-104075Article in journal (Refereed)
    Abstract [en]

    According to Belinskii, Khalatnikov and Lifshitz (BKL), a generic spacelike singularity is characterized by asymptotic locality: Asymptotically, toward the singularity, each spatial point evolves independently from its neighbors, in an oscillatory manner that is represented by a sequence of Bianchi type I and II vacuum models. Recent investigations support a modified conjecture: The formation of spatial structures (`spikes') breaks asymptotic locality. The complete description of a generic spacelike singularity involves spike oscillations, which are described by sequences of Bianchi type I and certain inhomogeneous vacuum models. In this paper we describe how BKL and spike oscillations arise from concatenations of exact solutions in a Hubble-normalized state space setting, suggesting the existence of hidden symmetries and showing that the results of BKL are part of a greater picture

  • 298. Heister, K.
    et al.
    Rong, H.-T.
    Buck, M.
    Zharnikov, M.
    Grunze, M.
    Johansson, Lars
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Odd-even efffects at the S-metal interface and in the aromatic matrix in biphenyl-substituted alkanethiol self-assembled monolayers2001In: Journal of Physical Chemistry B 105, 6888 (2001)Article in journal (Refereed)
    Abstract [en]

    Synchrotron-based high-resolution X-ray photoelectron spectroscopy was applied to characterize self-assembled monolayers (SAM) of biphenyl-substituted alkanethiols CH3(C6H4)2(CH2)nSH (BPn, n = 1-4) on Au and Ag substrates. Beyond previously identified odd-even changes in the packing density and the tilt angle of the biphenyl moieties, the high-resolution spectra reveal a number of additional odd-even effects upon variation of the number of methylene groups in the aliphatic part in the BPn molecule. Their occurrence and mutual correlation suggests that a BPn SAM represents a strongly correlated, highly ordered molecular assembly. In particular, periodical changes of a shake up feature in the C 1s region are observed, which are related to the differences in the arrangement of the aromatic matrix. The width and binding energy position of the S 2p signals also exhibit odd-even changes. The width changes are associated with the occupation of either equivalent or nonequivalent adsorption sites on the polycrystalline (111) Au and Ag substrates. The comparison of the width values with those for conventional alkanethiols implies that the substrate bonding of alkanethiols on gold cannot be described by a single adsorption site

  • 299. Heister, K.
    et al.
    Zharnikov, M.
    Grunze, M.
    Johansson, Lars
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Adsorption of alkanethiols and biphenylthiols on Au and Ag substrates: A high resolution X-ray photoelectron spectroscopy study2001In: Journal of Physical Chemistry B 105, 4058 (2001)Article in journal (Refereed)
    Abstract [en]

    Synchrotron-based high-resolution X-ray photoelectron spectroscopy was applied to monitor the formation of self-assembled monolayers (SAM) of alkanethiols (AT) and biphenylthiols on Au and Ag substrates. Pronounced chemical shifts in the adsorbate- and substrate-related photoemission lines upon SAM formation were observed. Only one sulfur species could be detected in the S 2p spectra of the investigated SAMs, consistent with a thiolate bond. From the fwhm's of the core level photoemission spectra conclusions on the heterogeneity of the adsorption sites and adsorption geometry can be made. The experimental data imply several (at least two) slightly different adsorption geometries for the AT moieties in AT/Au. Significant final state effects in the C 1s photoemission were found for both the aliphatic and aromatic SAMs

  • 300. Heister, K.
    et al.
    Zharnikov, M.
    Grunze, M.
    Johansson, Lars
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Ulman, A.
    Characterization of X-ray induced damage in alkanethiolate monolayers by high resolution photoelectron spectroscopy,2001In: Langmuir 17, 8 (2001)Article in journal (Refereed)
    Abstract [en]

    Synchrotron-based high-resolution X-ray photoelectron spectroscopy was for the first time applied to investigate the damage in self-assembled monolayers (SAMs) of alkanethiols (AT) on Au caused by soft X-rays. The observed changes in AT SAMs and, in particular, the appearance of a new, irradiation-induced sulfur species are identical to those caused by electron bombardment, implying that most of the damage is produced by the photoelectrons and secondary electrons. The irradiation-induced sulfur species is identified as a dialkyl sulfide distributed within the AT film. Only minutes of monochromatized X-ray irradiation at an undulator beamline destroys the AT adlayer completely.

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