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  • 101.
    Chavhan, Sudam D.
    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. Karlstad University, Faculty of Technology and Science, Materials Science.
    Solution Processed NiO Hole Transporting Layer in P3HT:PCBM Bulk Heterojunction Organic Solar Cells2011Conference paper (Refereed)
    Abstract [en]

    Despite of low fabrication cost and flexibility, limited life time is the major disadvantage of bulk heterojunction organic solar cells (OSCs). The main causes of short life time of OSCs is the degradation of active layer in presence of light and O2 and the effect of the acidic PEDOT:PSS on the ITO electrode. To overcome this problem PEDOT: PSS can be replaced by a p-type metal oxide hole transportation layer, such as NiO. There are reports on vacuum deposited NiO hole transporting layers in OSCs. Here, we have used the low-cost spin coating technique to deposit the NiO layer from a dispersion of NiO particles in methanol. Concentration and deposition parameters were optimized to obtain 40-50 nm thick layer of NiO as observed by tapping mode atomic force microscopy. The device performance of P3HT:PCBM solar cell with ITO/PEDOT: PSS and ITO/NiO electrodes was compared.

  • 102.
    Chuan Chen, Max
    et al.
    KTH.
    Omanakuttan, Giriprasanth
    KTH.
    Hansson, Rickard
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Strömberg, Axel
    KTH.
    Hallén, Anders
    KTH.
    Rinio, Markus
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Lourdudoss, Sebastian
    KTH.
    Sun, Yan-Ting
    KTH.
    Low temperature activation of B implantation of Si subcell fabrication in III-V/Si tandem solar cells2019In: Proceedings of the 36th EU PVSEC 2019, WIP, 2019, p. 764-768Conference paper (Other academic)
    Abstract [en]

    In this work, we investigated the Si pre-amorphization implantation (PAI) assisted low temperatureannealing process to activate boron implantation in n-Si in a hydride vapor phase epitaxy (HVPE) reactor, which canbe used for the Si subcell fabrication in the III-V/Si tandem solar cells enabled by the corrugated epitaxial lateralovergrowth (CELOG). A uniform boron activation in Si and a low emitter sheet resistance of 77 /sq was obtained atannealing temperatures of 600-700°C. High-resolution x-ray diffraction was used to study the recrystallization ofamorphous silicon and the incorporation of boron dopants in Si. Hall measurements revealed p-type carrierconcentrations in the order of 1020 cm-3. The n-Si wafers with B implantation activated at 700°C by HVPE wereprocessed to solar cells and characterized by the standard light-current-voltage measurement under AM1.5 spectrumand external quantum efficiency measurements. The developed B implantation and low temperature activationprocesses are applied to the InP/Si seed template preparation for CELOG, on which CELOG GaInP over a Si subcellwith a direct heterojunction was demonstrated.

  • 103.
    Ciammaruchi, Laura
    et al.
    Parc Mediterani de la Technologia, ICFO.
    Hansson, Rickard
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Moons, Ellen
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Galagan, Yulia
    TNO Solliance, Eindhoven, Netherlands.
    Stability of organic solar cells with PCDTBT donor polymer: An interlaboratory study2018In: Journal of Materials Research, ISSN 0884-2914, E-ISSN 2044-5326, Vol. 33, no 13, p. 1909-1924Article in journal (Refereed)
    Abstract [en]

    This work is part of the interlaboratory collaboration to study the stability of organic solar cells containing PCDTBT polymer as a donor material. The varieties of the OPV devices with different device architectures, electrode materials, encapsulation, and device dimensions were prepared by seven research laboratories. Sets of identical devices were aged according to four different protocols: shelf lifetime, laboratory weathering under simulated illumination at ambient temperature, laboratory weathering under simulated illumination, and elevated temperature (65 degrees C) and daylight outdoor weathering under sunlight. The results generated in this study allow us to outline several general conclusions related to PCDTBT-based bulk heterojunction (BHJ) solar cells. The results herein reported can be considered as practical guidance for the realization of stabilization approaches in BHJ solar cells containing PCDTBT.

  • 104. Cinà, S.
    et al.
    Baynes, N.
    Moons, Ellen
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Friend, R.H.
    Burroughes, J.
    Towns, C.
    Heeks, K.
    O'Dell, R.
    O'Conner, S.
    Athanassopoulou, N.
    New, Efficient Light Emitting Polymer Diode for Flat Panel Display Applications2001Conference paper (Refereed)
  • 105.
    Cirillo, Emilio
    et al.
    Sapienza Univ Roma, Dipartimento Sci Base & Appl Ingn, Via A Scarpa 16, I-00161 Rome, Italy.
    Krehel, Oleh
    Eindhoven Univ Technol, ICMS, Dept Math & Comp Sci, POB 513, NL-5600 MB Eindhoven, Netherlands.
    Muntean, Adrian
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    van Santen, Rutger
    Eindhoven Univ Technol, Fac Chem Engn, ICMS, POB 513, NL-5600 MB Eindhoven, Netherlands.
    Lattice model of reduced jamming by a barrier2016In: Physical review. E, ISSN 2470-0045, E-ISSN 2470-0053, Vol. 94, no 4, article id 042115Article in journal (Refereed)
  • 106.
    Cirillo, Emilio N.M.
    et al.
    Sapienza Universit`a di Roma, Italy.
    Colangeli, Matteo
    Moons, Ellen
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Muntean, Adrian
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Muntean, Stela Andrea
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    van Stam, Jan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    A lattice model approach to the morphology formation from ternary mixtures during the evaporation of one component2019In: The European Physical Journal Special Topics, ISSN 1951-6355, E-ISSN 1951-6401, Vol. 228, no 1, p. 55-68Article in journal (Refereed)
    Abstract [en]

    Stimulated by experimental evidence in the field of solution-born thin films, we study the morphology formation in a three state lattice system subjected to the evaporation of one component. The practical problem that we address is the understanding of the parameters that govern morphology formation from a ternary mixture upon evaporation, as is the case in the fabrication of thin films from solution for organic photovoltaics. We use, as a tool, a generalized version of the Potts and Blume-Capel models in 2D, with the Monte Carlo Kawasaki-Metropolis algorithm, to simulate the phase behaviour of a ternary mixture upon evaporation of one of its components. The components with spin 1, −1 and 0 in the Blume-Capel dynamics correspond to the electron-acceptor, electron-donor and solvent molecules, respectively, in a ternary mixture used in the preparation of the active layer films in an organic solar cell. Furthermore, we introduce parameters that account for the relative composition of the mixture, temperature, and interaction between the species in the system. We identify the parameter regions that are prone to facilitate the phase separation. Furthermore, we study qualitatively the types of formed configurations. We show that even a relatively simple model, as the present one, can generate key morphological features, similar to those observed in experiments, which proves the method valuable for the study of complex systems.

  • 107. Cirillo, E,N.M
    et al.
    Colangeli, M.
    Muntean, Adrian
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Stationary currents in particle systems with constrained hopping rates2016In: Journal of Non-Equilibrium Thermodynamics, ISSN 0340-0204, E-ISSN 1437-4358, Vol. 41, no 2, p. 99-106Article in journal (Refereed)
  • 108.
    Cirillo, E.N.M.
    et al.
    Univ Roma La Sapienza, Dipartimento Sci Base & Applicate Ingn, Rome, Italy.
    Krehel, O.
    Eindhoven Univ Technol, Inst Complex Mol Syst, Eindhoven, Netherlands.
    Muntean, Adrian
    Eindhoven Univ Technol, Inst Complex Mol Syst.
    van Santen, R.
    Eindhoven Univ Technol, Inst Complex Mol Syst, Eindhoven, Netherlands.
    Sengar, A.
    Indian Inst Technol Delhi, Delhi, India.
    Residence time estimates for asymmetric simple exclusion dynamics on strips2015In: Physica A: Statistical Mechanics and its Applications, ISSN 0378-4371, E-ISSN 1873-2119, Vol. 442, p. 436-457Article in journal (Refereed)
  • 109. Cricenti, A.
    et al.
    Selci, S.
    Magnusson, Kjell
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Reihl, B.
    On the position of the empty surface state band on Si(111)2x11990In: Phys. Rev. B 41, 12908 (1990)Article in journal (Refereed)
  • 110.
    Dahlin, Cecilia
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    De yngsta barnens möten med fysikaliska fenomen i förskolan: En undersökning om hur pedagogerna ger de yngsta barnen möjlighet att utforska och undersöka enkla fysikaliska fenomen2014Independent thesis Advanced level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The Swedish Schools Inspection shows in Education's Quality Review, Report 2012:7 that the majority of teachers in kindergarten needs to expand their knowledge of how they can work with science and how they can stimulate and challenge children's curiosity and learning in the field. Studies have shown that teachers in kindergarten often worry about asking questions and answering questions about science because of their lack of knowledge. In this study I have limited myself to see how the youngest children get the opportunity to develop an understanding and knowledge of physical phenomena. The purpose of this study is to show how and if teachers create meetings between the children and physical phenomena, so that children can gain understanding and knowledge. The result is based on qualitative interviews with ten preschool teachers.

    The result shows that the majority of respondents give the children opportunities to develop understandings and knowledge about physical phenomena, through planned activities or unplanned activities, but there were three respondents who didn’t give the children that opportunity at all. The results also show that the respondents do not seem to perceive children's exploration as scientific exploration; nor that their work supports children in developing their ability to work scientifically, by helping the children asking productive questions, making hypotheses and then examine them, which is the basis of scientific practice.

  • 111. 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)
  • 112.
    De Vin, Leo
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Plagiering: en moralisk fråga eller en pedagogisk utmaning?2012Other (Other (popular science, discussion, etc.))
    Abstract [sv]

    Artikeln beskriver plagiat men även otillåtet samarbete. Uppfattningarna om vad som räknas till plagiat varierar dock. Plagiat är inte lika med fusk, för fusk krävs uppsåt att vilseleda. Plagiat uppstår ofta när studenter känner tidspress eller osäkerhet. Lärare brukar upptäcka indikeringar på möjligt plagiat på manga olika sätt, det är relativt sällan att antiplagieringsverktyg larmar utan att läraren redan har fått misstankar. Sättet som plagiat hanteras på beror på ett antal faktorer, till exempel om studenten vet om korrekt källhantering eller ej. Inte alla fall av plagiat blir ärenden för disciplinsnämnden. Som lärare kan man förebygga plagiat på olika sätt. Dels handlar det om information och träning för studenter, dels handlar det om utformning av examinationsuppgifter, till exempel variation av uppgifter och muntlig återkoppling.

  • 113. Duda, L.
    et al.
    Johansson, Lars
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Reihl, B.
    Yeom, H. W.
    Hara, S.
    Yoshida, S.
    Angle-resolved photoemission studies of the 3C-SiC(001)(2 x 1) surface1999In: Surface Review and Letters 6, 1151 (1999)Article in journal (Refereed)
  • 114. Duda, L.
    et al.
    Johansson, Lars
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Reihl, B.
    Yeom, H. W.
    Hara, S.
    Yoshida, S.
    Electronic structure of the 3C-SiC(001)2 x 1 surface studied with angle-resolved photoelectron spectroscopy1999In: Surface Science 439, 199 (1999)Article in journal (Refereed)
  • 115. Duda, L.
    et al.
    Johansson, Lars
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Reihl, B.
    Yeom, H. W.
    Hara, S.
    Yoshida, S.
    Surface states of the 3C-SiC(001)-c(4×2) surface studied with angle-resolved photoemission2000In: Physical. Review B 61, R2460 (2000)Article in journal (Refereed)
  • 116.
    Duong, M. H.
    et al.
    University of Warwick, UK.
    Muntean, Adrian
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Richardson, Omar
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Discrete and continuum links to a nonlinear coupled transport problem of interacting populations2017In: The European Physical Journal Special Topics, ISSN 1951-6355, E-ISSN 1951-6401, Vol. 226, no 10, p. 2345-2357Article in journal (Refereed)
    Abstract [en]

    We are interested in exploring interacting particle systemsthat can be seen as microscopic models for a particular structure ofcoupled transport flux arising when different populations are jointlyevolving. The scenarios we have in mind are inspired by the dynamicsof pedestrian flows in open spaces and are intimately connectedto cross-diffusion and thermo-diffusion problems holding a variationalstructure. The tools we use include a suitable structure of the relativeentropy controlling TV-norms, the construction of Lyapunov functionalsand particular closed-form solutions to nonlinear transport equations,a hydrodynamics limiting procedure due to Philipowski, as wellas the construction of numerical approximates to both the continuumlimit problem in 2D and to the original interacting particle systems.

  • 117.
    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.
    Moons, Ellen
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    The effect of light exposure on P3HT:PCBM films: a NEXAFS study2011Conference paper (Refereed)
    Abstract [en]

    A simple photolithography method was developed for patterning organic field effect transistors (OFETs) prepared from blends of poly(3-hexylthiophene), P3HT, and [6,6]-phenyl-C61-butyric acid methyl ester, PCBM.(1) This Photo-induced and Resist-free Imprint patterning (PRI) technique allows also the single solution step production of organic CMOS circuits.(2) It consists of two subsequent processing steps: 1) exposure: photo-irradiation of the P3HT:PCBM blend by visible laser light and 2) development: rinsing of the film in an organic solvent mixture that is selective for PCBM. As a result, two electronically different materials are obtained, i.e. the exposed and developed (ED) material, and the unexposed and developed (UD) material. The method is based on the modification of the PCBM component in the irradiated area, which becomes effectively insoluble in the solvent mixture, while the PCBM in the non-irradiated area is removed during development. Therefore, we expect that the UD material is pure P3HT, a hypothesis that is confirmed by the p-type conductivity of the ED region. Near-Edge X-ray Absorption Fine Structure spectroscopy (NEXAFS) was used to determine the surface composition of these films. C K-edge NEXAFS spectra of pristine, photo-exposed, and developed blend films, as well as films of the pure components were measured at the synchrotron facility MAX-lab in Lund, Sweden. The spectra for P3HT and PCBM are significantly different and the components can be clearly distinguished in the blend spectra. From the relative intensities of the P3HT and PCBM peaks, the actual blend composition can be estimated, both on the surface, using partial electron yield (PEY), and deeper in the sub-surface region of the film, using total electron yield (TEY). From the similarity of the spectra of the UD blend sample and the pure P3HT sample, we conclude that the remaining material after washing the pristine blend is indeed P3HT, and the ED blend sample retains its two-component character. The surface composition of the blend films is significantly more polymer-rich than the bulk blend ratio used to prepare the film. Both for the pristine blend and the photo-exposed blend differences are observed between the PEY and TEY spectra, indicating the existence of a polymer-enriched surface. Such gradients in thin films of P3HT:PCBM blends have been observed by others using variable-angle spectroscopic ellipsometry,(3) NEXAFS,(4) and neutron reflectometry,(5) and also in other polymer:PCBM blends by dynamic secondary ion mass spectrometry (d-SIMS).(6)

    References (1) Dzwilewski, A.; Wagberg, T.; Edman, L. J. Am. Chem.Soc. 2009, 131, 4006. (2) Dzwilewski, A.; Matyba, P.; Edman, L. J. Phys. Chem. B 2010, 114, 135. (3) Campoy-Quiles, M., et al., Nature Materials 2008, 7,158-164 (4) Germack,D.S. et al., Appl. Phys. Lett. 2009, 94, 233303. (5) Kiel, J.W. et al., Soft Matter 2010, 6, 641-646. (6) Björström, C.M. et al, J. Phys.: Condens. Matter 2005, 17, L529-L534.

  • 118.
    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)
  • 119.
    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)
  • 120. Díaz-Herrera, B.
    et al.
    Montesdeoca-Santana, Amada
    Jiménez-Rodriguez, E.
    González-Díaz, B.
    Hernández Rodríguez, C.
    Guerrero-Lemus, Ricardo
    Rinio, Markus
    Borchert, Dietmar
    Upgraded metallurgical grade silicon for solar cell fabrication2009Conference paper (Other academic)
  • 121. Dütemeyer, T.
    et al.
    Johansson, Lars
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Quitmann, C.
    Reihl, B.
    Imaging of the electronic states on the Si(111)1×1-As surface using a display-type photoelectron analyzer2001In: Surface Science 482-485, 600 (2001)Article in journal (Refereed)
    Abstract [en]

    e have measured the electronic structure of the arsenic-terminated Si(1 1 1)1×1As surface with angle-resolved photoemission using a display-type analyzer. The analyzer records energy-resolved angular distribution patterns of the photoelectrons in a solid angle of ?=43° and ?=360°, thereby covering the entire surface Brillouin zone at the binding energies measured here. Using this instrument we have mapped the entire two-dimensional dispersion of the lone-pair surface state, from the band maximum at to the global minima at the -points. In addition, the two-dimensional dispersions of the three upper valence bands are mapped, showing their threefold symmetry, using a photon energy of 21.2 eV. Our results are in good agreement with previous experiments and earlier quasiparticle band structure calculations

  • 122. Dütemeyer, T.
    et al.
    Quitmann, C.
    Kitz, M.
    Dörnemann, K.
    Johansson, Lars
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Reihl, B.
    Photoelectron Imaging using an Elliptical Display Analyzer2001In: Review of Scientific Instruments 72, 2638 (2001)Article in journal (Refereed)
  • 123. 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

  • 124.
    Edvardsson, Elisabet
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Band structures of topological crystalline insulators2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Topological insulators and topological crystalline insulators are materials that have a bulk band structure that is gapped, but that also have toplogically protected non-gapped surface states. This implies that the bulk is insulating, but that the material can conduct electricity on some of its surfaces. The robustness of these surface states is a consequence of time-reversal symmetry, possibly in combination with invariance under other symmetries, like that of the crystal itself. In this thesis we review some of the basic theory for such materials. In particular we discuss how topological invariants can be derived for some specific systems. We then move on to do band structure calculations using the tight-binding method, with the aim to see the topologically protected surface states in a topological crystalline insulator. These calculations require the diagonalization of block tridiagonal matrices. We finish the thesis by studying the properties of such matrices in more detail and derive some results regarding the distribution and convergence of their eigenvalues.

  • 125.
    Edvardsson, Elisabet
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Quasicrystals: Classification, diffraction and surface studies2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Quasicrystal is the term used for a solid that possesses an essentially discrete diffraction pattern without having translational symmetry. Compared to periodic crystals, this difference in structure gives quasicrystals new properties that make them interesting to study -- both from a mathematical and from a physical point of view. In this thesis we review a mathematical description of quasicrystals that aims at generalizing the well-established theory of periodic crystals. We see how this theory can be connected to the cohomology of groups and how we can use this connection to classify quasicrystals. We also review an experimental method, NIXSW (Normal Incidence X-ray Standing Waves), that is ordinarily used for surface structure determination of periodic crystals, and show how it can be used in the study of quasicrystal surfaces. Finally, we define the reduced lattice and show a way to plot lattices in MATLAB. We see that there is a connection between the diffraction pattern and the reduced lattice and we suggest a way to describe this connection.

  • 126.
    Ekhagen, Sebastian
    Karlstad University, Faculty of Health, Science and Technology (starting 2013).
    Silicon solar cells: basics of simulation and modelling: Using the mathematical program Maple to simulate and model a silicon solar cell2017Independent thesis Basic level (degree of Bachelor), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [en]

    The main goal of this thesis was to simulate a solar cell with the symbolic manipulation tool Maple and discuss the strength and weaknesses of using Maple instead of the already known simulation program PC1D. This was done mainly by solving the three essential differential equations governing the current density and excess electron and hole densities in the solar cell. This could be done easily by using known simplifications especially the low injection assumption. However it was also a success without using this particular simplification but the solutions had to be achieved using a numerical method instead of direct methods. The results were confirmed by setting up the same solar cell with PC1D. The conclusion is that Maple gives the user increased freedom when setting up the solar cell, however PC1D is easier to use if this freedom is not needed. At the end of this thesis a brief introduction is also made on the possibility of using Maple with a tandem cell setup instead of single junction.

  • 127.
    Ekström, Nina
    Karlstad University, Faculty of Arts and Social Sciences (starting 2013), Department of Educational Studies.
    Barns hypoteser och initiativ i en fysikaktivitet om flytkraft: En studie om barns initiativ ien problemlösande aktivitet om flyta-sjunka2018Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The purpose of the study is to find out how five-year-old children explain and find solutions in relation to a problem-solving experiment around the physical phenomenon float-sink. The method that was opted to use was video observation. The study is based on a video observation that lasted for 25 minutes with four children who were around five years old. The activity was divided into two different parts, the first part focused on hypotheses around the outcome of different objects in water, if they would either float or sink. The other part focused on problem solving, where the children should get something that earlier sank to float. The result of the study shows that the children focused on weight, form and size of the objects, in predicting whether they would sink or float. The children also show a big interest and take initiative to solve the problem that they were given in the beginning of the activity. They construct and shape the different materials and they succeed by creating an aluminium boat that could carry a pinecone and three stones.

  • 128.
    Emanuelsson, Christian
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Electronic Structure and Film Morphology Studies of PTCDI on Metal/Semiconductor Surfaces2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Organic semiconductors have received increasing attention over the last decades as potential alternatives for inorganic semiconductors. The properties of these films are highly dependent on their structural order. Of special interest is the interface between the film and its substrate, since the structure of the interface and the first few layers decide the growth of the rest of the film. The interface structure is determined by the substrate/molecule interactions, the intermolecular interactions and the growth conditions.

    In this thesis, thin films of the organic semiconductor PTCDI have been studied using complementary microscopy and spectroscopy techniques on two metal-induced surface reconstructions, Ag/Si(111)-√3×√3 and Sn/Si(111)-2√3×2√3. These surfaces were chosen because they have different reactivities and surface periodicities. On the weakly interacting Ag-terminated surface, the film growth is mainly governed by the intermolecular interactions. This leads to well-ordered films that grow layer-by-layer. The interaction with the substrate is through electron charge transfer to the molecules from the substrate. This results in two different types of molecules with different electronic structure, which are identified using both STM images and PES spectra. On the more strongly interacting Sn-terminated surface the molecules adsorb in specific adsorption geometries and form 1D rows. At around 0.5 ML coverage the rows also interact with each other and form a 4√3×2√3 reconstruction and beyond one ML coverage the growth is characterized as island growth. The interaction with the substrate is mainly due to heavy electron charge transfer from the Sn atoms in the substrate to the C atoms in the imide group, but also the N atoms and the perylene core in PTCDI are involved. In these systems, the interactions with the surfaces result in new states inside the HOMO-LUMO gap, and the intermolecular interactions are dominated by O···H and O···H-N hydrogen bondings.

  • 129.
    Emanuelsson, Christian
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Johansson, Lars
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Zhang, Hanmin
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Delicate Interactions of PTCDI molecules on Ag/Si(111)-√3×√32018In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 149, no 16, p. 164707-Article in journal (Refereed)
    Abstract [en]

    PTCDI molecules were evaporated onto a Ag/Si(111)√3×√3 surface and studied using scanning tun-resolution STM images are used to identify the delicate molecule/molecule and molecule/substrate interactions and the shapes of the molecular orbitals. The results show that the substrate/molecule interaction strongly modifies the electronic configuration of the molecules as their orbital shapes are quite different at 1 and 2 monolayer (ML) coverage. Simple models of molecular HOMO/LUMO levels and intermolecular hydrogen-bondings have been made for 1 and 2 ML PTCDI coverages to explain the STM images. Changes due to the interaction with the substrate are also found in ARUPS as extra states above the regular HOMO level at 1 ML PTCDI coverage. The ARUPS data also show that the electronic structure of the substrate remains unchanged after the deposition of molecules as the dispersion of the substrate related bands is unchanged. The changes in electronic structure ofthe molecules are discussed based on aHOMO/LUMO split.

  • 130.
    Emanuelsson, Christian
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Johansson, Lars
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Zhang, Hanmin
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Photoelectron spectroscopy studies of PTCDI on Ag/Si(111)-root 3 x root 32018In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 149, no 4, article id 044702Article in journal (Refereed)
    Abstract [en]

    3,4,9,10-perylene tetracarboxylic diimide molecules were evaporated onto a Ag/Si(111)-root 3 x root 3 surface and studied using photoelectron spectroscopy and near edge X-ray absorption fine structure (NEXAFS). All core levels related to the imide group of the molecules showed a partial shift to lower binding energies at low coverages. In NEXAFS spectra, the first transitions to the unoccupied states were weaker at low coverages compared to thicker films. Also, extra states in the valence band between the regular highest occupied molecular orbital and the Fermi level were found at low coverages. These changes were explained by two types of molecules. Due to charge transfer from the surface, these two types have different interactions between the imide group and the substrate. As a result, one type has a partially filled lowest unoccupied molecular orbital while the other type does not. Published by AIP Publishing.

  • 131.
    Emanuelsson, Christian
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Johansson, Lars
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Zhang, Hanmin
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Photoelectron spectroscopy studies of PTCDI on Sn/Si(111)-2√3×2√3Manuscript (preprint) (Other academic)
  • 132.
    Emanuelsson, Christian
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Soldemo, Markus
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Johansson, Lars
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Zhang, Hanmin
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Scanning tunneling microscopy study of PTCDI on Sn/Si(111)-2√3×2√32019In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 150, no 4Article in journal (Refereed)
    Abstract [en]

    Perylene tetracarboxylic diimide molecules were evaporated onto a Sn/Si(111)-2 root 3 x 2 root 3 surface and studied using scanning tunneling microscopy (STM) and low energy electron diffraction. At low coverages, single molecules are locked into specific adsorption geometries, which are investigated in detail using high resolution STM. The electronic structure of these individual molecules was studied using bias dependent STM images. The molecules form 1D rows that become more common with increasing coverages. Possible intermolecular O center dot center dot center dot H interactions within the rows have been identified. At around half of a monolayer (ML), the rows of molecules interact with each other and form a commensurate 4 root 3 x 2 root 3 reconstruction. In a complete monolayer, several structures emerge as molecules fill in the space between the 4 root 3 x 2 root 3 stripes. Possible intermolecular interactions within the 1 ML structures have been discussed. At coverages above 1 ML, the growth is characterized by island growth, where the molecules are arranged according to the canted structure within the layers.

  • 133.
    Emanuelsson, Christian
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Zhang, Hanmin
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Moons, Ellen
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Johansson, Lars
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Scanning tunneling microscopy study of thin PTCDI films on Ag/Si(111)-root 3 x root 32017In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 146, no 11, article id 114702Article in journal (Refereed)
    Abstract [en]

    3,4,9,10-perylene tetracarboxylic diimide molecules were evaporated onto a Ag/Si(111)-root 3 x root 3 surface and studied by scanning tunneling microscopy/spectroscopy and low energy electron diffraction (LEED). The growth mode was characterized as layer-by-layer growth with a single molecular unit cell in a short range order. The growth of the first two monolayers involves a molecule/substrate superstructure and a molecule/molecule superstructure. At higher coverages, the molecules in each layer were found to align so that unit cells are on top of each other. The experimentally obtained LEED pattern is described as a combination of patterns from the molecular unit cell and the molecule/substrate superstructure. The electronic structure was found to be strongly dependent on the film thickness for the first few layers: Several extra states are found at low coverages compared to higher coverages resulting in a very small pseudo gap of 0.9 eV for the first layer, which widens up to 4.0 eV for thicker films.

  • 134.
    Enghag, Margareta
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Arbete med en egen frågeställning som ger lärande i fysik om ownership of learning2006In: In: Bering, Dolin, Krogh, Sølberg, Sørensen och Troelsen Naturfagsdidaktikkens mange facetter. Proceedings fra Det 8. nordiske forskersymposium om undervisning i naturfag (Aalborg 2005), Køpenhavn: Danmarks pædagogiske Universitets Forlag, 193- 200) , 2006Chapter in book (Refereed)
  • 135.
    Enghag, Margareta
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Miniprojects and Context Rich Problems: Case studies with qualitative analysis of motivation, learner ownership and competence in small group work in physics2004Licentiate thesis, monograph (Other academic)
    Abstract [sv]

    This thesis reports case studies of students working with context rich problems (CRP) and mini projects (MP) in physics in an upper secondary school class and in a physics teacher education class at university. The students report a big shift from physics in secondary school as fun and easy, to physics in upper secondary school as boring, difficult and with lack of time for reflections and physics talking, but they also found physics as interesting in itself. In order to study how group discussions in physics influence the students learning and to study the phenomena of students ownership of learning (SOL) we introduced CRP and MP. We video recorded five groups with 14 teacher students at university in the end of 2002, and five group with 15 students at upper secondary school during the beginning of their second physics course in the spring term in 2003. MP and CRP in physics were used as instructional settings in order to give students possibility to strengthen their holistic understanding and their possibilities to ownership. When students get the opportunity to manage their own learning and studying by open-ended tasks in physics, without the teacher determining all details of the performance, this gives more ownership of learning. The advantage of MPs and CRPs from the students point of view is more freedom to act, think and discuss and from the teachers view, to get insights of the students ability and how they really think in physics. The ownership is found to be crucial for motivation and development of competence.



    Students ownership of learning (SOL) is the students influence/impact to affect tasks and the learning environment in such a way that the students have a real opportunity to achieve learning of physics.



    Students ownership of learning (SOL) is found at two levels:



    Group level: At the start of a task the SOL is determined by the design of the task. The choice of task, the performance (when, how, where), the level of result and presentatio n and report have to be determined by the students themselves.



    Individual level: A persons experiences and anomalies of understanding have created unique questions that can create certain aspects of the task that drive this person to be very active and highly motivated. This gives the person a high individual ownership. We developed hypotheses concerning the relation between ownership, motivation and competence and we see some evidence in the cases reported in this thesis. The importance of exploratory talks to enhance learning, and to see aspects of communication as part of the motivation are discussed in the model of ownership, motivation and competence that is proposed

  • 136.
    Enghag, Margareta
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    The importance of interaction and talk to enhance physics understanding2010Conference paper (Refereed)
  • 137.
    Enghag, Margareta
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Two dimensions of student ownership of learning during small-group work with miniprojects and context rich problems in physics2006Doctoral thesis, monograph (Other academic)
    Abstract [en]

    In this thesis the theoretical framework student ownership of learning (SOL) is developed both theoretically and with qualitative research, based on studies of small-group work in physics with miniprojects and context rich problems. Ownership is finally defined as actions of choice and control, i.e. the realised opportunities to own organisation of the work. The dimension group ownership of learning refers to the groups actions of choice and control of the management of the task: how the task is determined, performed and finally reported. The other dimension, the individual student ownership of learning, refers to the individual student's own question/idea that comes from own experiences, interests, or anomalies of understanding; an idea/question that recurs several times and leads to new insights. From literature and from own data, categories are constructed for group and individual student ownership of learning, which have been iteratively sharpened in order to identify ownership in these two dimensions. As a consequence, the use of the framework student ownership of learning is a way to identify an optimal level of ownership for better learning and higher motivation in physics teaching.The first part of the thesis gives an overview of the theoretical background to the studies made, and summarises the findings. The second part consists of six articles that report case studies with analyses of audio/video-recorded student cooperative work, and student group discussions, from three collections of data: 1) students working with miniprojects in teacher education, 2) upper secondary school students taking a physics course that includes both context rich problems with group discussions and miniprojects, and 3), aeronautical engineering students working with context rich problems in an introductory physics course at university.The thesis describes in a fine-grained analysis the conversation in the groups based on Barnes discourse moves, and finds that ownership and communication are related. Group discussions are found to be an indicator for group ownership of learning and exploratory talks often promotes individual student ownership of learning

  • 138.
    Enghag, Margareta
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    University students personal ideas about school physics as starting point for dialogic/interactive talk2008Conference paper (Refereed)
  • 139.
    Enghag, Margareta
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Forsman, Jonas
    Department of Physics and Astronomy, Uppsala University, Sweden.
    Linder, Cedric
    Department of Physics and Astronomy, Uppsala University, Sweden.
    MacKinnon, Allan
    Faculty of Education, Simon Fraser University, Burnaby, BC, Canada, V5A 1S6.
    Moons, Ellen
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Using a disciplinary discourse lens to explore how representations afford meaning making in a typical wave physics course2013In: International Journal of Science and Mathematics Education, ISSN 1571-0068, E-ISSN 1573-1774, Vol. 11, no 3, p. 625-650Article in journal (Refereed)
    Abstract [en]

    We carried out a case study in a wave physics course at a Swedish university in order to investigate the relations between the representations used in the lessons and the experience of meaning making in interview–discussions. The grounding of these interview–discussions also included obtaining a rich description of the lesson environment in terms of the communicative approaches used and the students’ preferences for modes of representations that best enable meaning making. The background for this grounding was the first two lessons of a 5-week course on wave physics (70 students). The data collection for both the grounding and the principal research questions consisted of video recordings from the first two lessons: a student questionnaire of student preferences for representations (given before and after the course) and video-recorded interview–discussions with students (seven pairs and one on their own). The results characterize the use of communicative approaches, what modes of representation were used in the lectures, and the trend in what representations students’ preferred for meaning making, all in order to illustrate how students engage with these representations with respect to their experienced meaning making. Interesting aspects that emerged from the study are discussed in terms of how representations do not, in themselves, necessarily enable a range of meaning making; that meaning making from representations is critically related to how the representations get situated in the learning environment; and how constellations of modes of disciplinary discourse may be necessary but not always sufficient. Finally, pedagogical comments and further research possibilities are presented.

  • 140.
    Enghag, Margareta
    et al.
    Mälardalen University.
    Gustafsson, Peter
    Mälardalen University.
    Jonsson, Gunnar
    Mälardalen University.
    Context Rich Problems and Miniprojects in Physics for Upper Secondary School2004In: Science Education International, ISSN 2077-2327, Vol. 15, no 4, p. 293-302Article in journal (Refereed)
  • 141.
    Enghag, Margareta
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Gustafsson, Peter
    Jonsson, Gunnar
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    From everyday life experiences to physics understanding occurring in small group work with context rich problems during introductory physics work at university2007In: Research in Science Education, 37:449-467Article in journal (Refereed)
  • 142.
    Enghag, Margareta
    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. Karlstad University, Faculty of Technology and Science, Materials Science.
    Forsman, Jonas
    Department of Physics and Astronomy, Uppsala University, Sweden.
    Wikman, Susanne
    Andersson, Steffan
    Department of Physics and Astronomy, Uppsala University, Sweden.
    Linder, Cedric
    Department of Physics and Astronomy, Uppsala University, Sweden.
    Student evaluations of themselves as disciplinary practitioners2009Conference paper (Other academic)
  • 143.
    Enghag, Margareta
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Niedderer, H
    Physics learning with exploratory talks during a miniproject - a case study of four girls working with electric circuits2005In: Journal of Baltic Science Education,1(7), (5-11)Article in journal (Refereed)
  • 144.
    Enghag, Margareta
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Niedderer, Hans
    Two Dimensions of Student Ownershipof Learning During Small-Group Work in Physics2008In: International Journal of Science and Mathematics Education 6:629-653Article in journal (Refereed)
    Abstract [en]

    The theoretical framework student ownership of learning is developed both theoretically and with qualitative research. The metaphor ownership is related to the process towards meaning making and understanding and is seen as relevant especially to improve physics instruction. The dimension group ownership of learning refers to the groups actions of choice and control of the management of the task; how the task is determined, performed and finally reported. The other dimension, the individual student ownership of learning, refers to an individual students own question/idea that comes from own experiences, interests or anomalies of understanding; an idea/question that comes back several times and leads to new insights. From literature and from our own data, we have developed categories for group and individual student ownership of learning, which were iteratively sharpened in order to identify ownership in the two dimensions. As a consequence, we argue for use of the framework student ownership of learning as a way to identify an optimal level of ownership for better learning and higher motivation in physics teaching

  • 145.
    Enghag, Margareta
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Wahlquist, B
    Hell, L
    Emergent Dialogic Teaching of Newtons Second Law2009Conference paper (Refereed)
  • 146.
    Ericsson, Leif
    Karlstad University, Division for Engineering Sciences, Physics and Mathematics.
    Silicon/Germanium Molecular Beam Epitaxy2006Independent thesis Advanced level (degree of Magister), 20 points / 30 hpStudent thesis
    Abstract [en]

    Molecular Beam Epitaxy (MBE) is a well-established method to grow low-dimensional structures for research applications. MBE has given many contributions to the rapid expanding research-area of nano-technology and will probably continuing doing so. The MBE equipment, dedicated for Silicon/Germanium (Si/Ge) systems, at Karlstads University (Kau) has been studied and started for the first time. In the work of starting the system, all the built in interlocks has been surveyed and connected, and the different subsystems has been tested and evaluated. Service supplies in the form of compressed air, cooling water and electrical power has been connected. The parts of the system, their function and some of the theory behind them are described.

    The theoretical part of this master’s thesis is focused on low-dimensional structures, so-called quantum wells, wires and dots, that all are typical MBE-built structures. Physical effects, and to some extent the technical applications, of these structures are studied and described.

    The experimental part contains the MBE growth of a Si/Ge quantum well (QW) structure and characterisation by Auger Electron Spectroscopy (AES). The structure, consisting of three QW of Si0,8Ge0,2 separated by thicker Si layers, was built at Linköpings University (LiU) and characterised at Chalmers University of Technology (CTH). The result of the characterisation was not the expected since almost no Ge content could be discovered but an extended characterisation may give another result.

    Keywords: Silicon, Germanium, Molecular Beam Epitaxy, MBE, Quantum wells

  • 147.
    Ericsson, Leif
    et al.
    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).
    Blazinic, Vanja
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Moons, Ellen
    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).
    Effects of the morphology on the photodegradation of TQ1:PC70BM film: an AFM-IR studyManuscript (preprint) (Other academic)
  • 148.
    Ericsson, Leif
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Grützelius Hirvonen, Helena
    Magnusson, Kjell
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Controlled distribution of ZnO nanoparticles on Si/SiO2 surfaces2007Conference paper (Other academic)
    Abstract [en]

    Controlled distribution of ZnO nanoparticles on Si/SiO2 surfacesIn recent years the properties and applications of ZnO nanomaterials has been extensively examined, partly due to the potential of ZnO as UV and visible light emitter and detector. Much of the previous work concern synthesis and growth of ZnO in different forms. In this survey, we have primarily studied commercially available nanoparticles and how they can be distributed on surfaces, aiming for future applications in e.g. photovoltaic devices. Later custom synthesised ZnO particles will be used in collaboration with Prof. Gunnar Westin at Uppsala University.ZnO nanoparticles, non-coated and organo-silane coated, with an average size of 70 nm from Alfa Aesar GmbH & Co KG, Germany, have been used in different dispersions for application on surfaces and the aim has been to achieve a controllable distribution of particles. In order to achieve this, different substrate preparations, solvents for dispersion and application methods have been used. Characterisation of the particle distribution has been done with Optical Microscopy (OM), Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM). The chemical and the crystallographic properties of the particles have also been investigated using Auger Electron Spectroscopy (AES) and X-ray Diffraction (XRD).The substrates used are Si(001) with different preparations to create hydrophobic or hydrophilic surfaces. Nanoparticles were applied to the substrates using drop-coating and spin-coating. Several different solvents, including water, 1,2-PMA and chloroform, have been used for dispersions, yielding the possibility to use vapour pressure and solubility parameters to control the distribution. Separated particles are observed in all of the examined samples below a certain ZnO concentration. The amount of separated particles is dependent on the surface used, the solvent and the preparation procedure. A trend that can be followed from micro-scale to nano-scale is that smaller agglomerates correspond to more separated particles. Particles of different forms have been identified for later characterization.

  • 149.
    Ericsson, Leif K E
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Magnusson, Kjell
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Zhang, Hanmin
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    AFM and STM Study of ZnO NanoplatesManuscript (preprint) (Other academic)
    Abstract [en]

    The surface morphology and electronic structure of hexagonal ZnO nanoplates have been studied by Atomic Force Microscopy (AFM) and Scanning Tunneling Microscopy (STM). It was found that these nanoplates are terminated by their polar (0001) surfaces. The AFM investigation was performed in the ambient conditions with the nanocrystals “as grown”. Surprisingly, the AFM images of the top surfaces revealed an interesting triangular reconstruction, which was earlier observed only after cycles of sputtering and annealing of the ZnO(0001) surface in Ultra High Vacuum (UHV) systems. The surface atomic and electronic structures of these nanoplates have been further studied by STM and Scanning Tunneling Spectroscopy (STS) in UHV. The STM images also showed a triangular structure with single atomic steps. In addition, a 2x2 surface reconstruction has been observed with high resolution STM. This reconstruction agrees well with the recently proposed model that involves the removal of 1/4 of the topmost Zn atoms on the ZnO(0001) surface.

  • 150.
    Ericsson, Leif KE
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Growth and Characterization of ZnO Nanocrystals2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The understanding of surfaces of materials is of crucial importance to all of us. Considering nanocrystals (NCs), that have a large surface to bulk ratio, the surfaces become even more important. Therefore, it is important to understand the fundamental surface properties in order to use NCs efficiently in applications. In the work reported in this thesis ZnO NCs were studied.

    At MAX-lab in Lund, synchrotron radiation based Spectroscopic Photoemission and Low Energy Electron Microscopy (SPELEEM) and X-ray Photoelectron Spectroscopy (XPS) were used. At Karlstad University characterization was done using Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Atomic Force Microscopy (AFM), Scanning Tunnelling Microscopy (STM), Auger Electron Spectroscopy (AES), and XPS.

    The fundamental properties of ZnO surfaces were studied using distributions of ZnO NCs on SiO2/Si surfaces. The conditions for distribution of ZnO NCs were determined to be beneficial when using ethanol as the solvent for ultrasonically treated dispersions. Annealing at 650 °C in UHV cleaned the surfaces of the ZnO NCs enough for sharp LEEM imaging and chemical characterization while no sign of de-composition was found. A flat energy band structure for the ZnO/SiO2/Si system was proposed after 650 °C. Increasing the annealing temperature to 700 °C causes a de-composition of the ZnO that induce a downward band bending on the surfaces of ZnO NCs.

    Flat ZnO NCs with predominantly polar surfaces were grown using a rapid microwave assisted process. Tuning the chemistry in the growth solution the growth was restricted to only plate-shaped crystals, i.e. a very uniform growth. The surfaces of the NCs were characterized using AFM, revealing a triangular reconstruction of the ZnO(0001) surface not seen without surface treatment at ambient conditions before. Following cycles of sputtering and annealing in UHV, we observe by STM a surface reconstruction interpreted as 2x2 with 1/4 missing Zn atoms.

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