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  • 51.
    Hirvonen Grytzelius, Joakim
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för fysik och elektroteknik. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap.
    Zhang, Hanmin
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för fysik och elektroteknik.
    Johansson, Lars
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för fysik och elektroteknik.
    Mn5Ge3 film formation on Ge(111)c(2×8)2012Inngår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 86, nr 12, s. 125313-1-125313-7Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Thin manganese germanide films with different thicknesses on Ge(111) have been studied in detail by low-energy electron diffraction (LEED), scanning tunneling microscopy, and core-level spectroscopy (CLS). Annealing of the deposited Mn on Ge(111)c(2×8) between 330-450 C resulted in well-ordered Mn5Ge3 surfaces as seen by intense 3×3 LEED spots. Up to a coverage of 24 monolayers (ML), island formation is favored. At a coverage of 32 ML a well ordered Mn5Ge3 film was found to fully cover the surface. High-resolution Ge 3d CLS spectra were recorded with photon energies between 50 and 110 eV at normal and 60 emission angles. In contrast to earlier results, three components have been used in the line-shape analysis to achieve a consistent fit over the energy and angular range. In addition, three components have been identified for the Mn 2p CLS spectra. The two major components fit well with a layered Mn germanide structure suggested in the literature.

  • 52.
    Hirvonen Grytzelius, Joakim
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för fysik och elektroteknik.
    Zhang, Hanmin
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för fysik och elektroteknik.
    Johansson, Lars
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för fysik och elektroteknik.
    Surface atomic and electronic structure of Mn5Ge3 on Ge(111)2011Inngår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, ISSN 1098-0121, Vol. 84, nr 19, s. 195306-1-195306-6Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The atomic and electronic structure of the Mn5Ge3(001) surface grown on Ge(111) c(2×8) has been studied in detail by angle-resolved photoelectron spectroscopy (ARPES), scanning tunneling microscopy (STM), and scanning tunneling spectroscopy. ARPES spectra recorded from the Γ̅ -K̅ -M̅ and Γ̅ -M̅ -Γ̅ directions of the surface Brillouin zone show six surface-related features. The STM images recorded at biases higher/lower than ±0.4 V always show a honeycomb pattern with two bright protrusions in each unit cell. At lower biases, a hexagonal, intermediate transition, and a honeycomb pattern are observed. These can be explained as arising from Mn and Ge atoms in the sublayer arranged in triangular structures and Mn atoms in the top layer arranged in a honeycomb structure, respectively. The photoemission and STM data from the germanide surface are discussed and compared to earlier published theoretical, photoelectron spectroscopy, and scanning tunneling microscopy studies.

  • 53.
    Hirvonen Grytzelius, Joakim
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för fysik och elektroteknik.
    Zhang, Hanmin
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för fysik och elektroteknik.
    Johansson, Lars
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för fysik och elektroteknik.
    Surface electronic structure of Mn/Si(111)-√3×√32008Inngår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 78, nr 15, s. 155406-1-155406-6Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The Mn/Si(111)-√3×√3 surface has been studied in detail by low energy electron diffraction (LEED), angle-resolved photoelectron spectroscopy (ARPES), and core-level photoelectron spectroscopy (CLS). Annealing of the deposited manganese resulted in a well-ordered surface as seen by intense √3×√3 LEED spots. ARPES spectra recorded in the Γ̅ -K̅ -M̅ direction of the √3×√3 surface Brillouin zone show five surface related features in the band gap while in the Γ̅ -M̅ -Γ̅ direction four surface features are observed. The high-resolution Si 2p CLS data were recorded at photon energies between 108–140 eV both at normal and 60° emission angle. The bulk component was identified from the bulk sensitive spectrum recorded at a photon energy of 108 eV. To achieve a consistent core-level fitting over the whole energy and angular range, five components were introduced in the line-shape analysis. The photoemission data from the √3×√3 surface have been discussed and compared with a recent theoretical model. The findings here support a layered Mn silicide film structure.

  • 54. Horzel, Jörg
    et al.
    Seidl, A.
    Buss, W.
    Westram, I.
    Mosel, F.
    Guenther, S.
    Novak, J.
    Sticksel, J.
    Blendin, G.
    Jahn, M.
    Rinio, Markus
    von Campe, H.
    Schmidt, W.
    Inherent material quality advantages for thin EFG si solar cells compared to thick EFG si solar cells2007Konferansepaper (Annet vitenskapelig)
  • 55.
    Hörmann, Ulrich
    et al.
    Institute of Physics, University of Augsburg, Universitätsstraße 1, 86135 Augsburg, Germany.
    Lorch, Christopher
    Institute of Applied Physics, University of Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany.
    Hinderhofer, Alexander
    Institute of Applied Physics, University of Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany.
    Gerlach, Alexander
    Institute of Applied Physics, University of Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany.
    Gruber, Mark
    Institute of Physics, University of Augsburg, Universitätsstraße 1, 86135 Augsburg, Germany.
    Kraus, Julia
    Institute of Physics, University of Augsburg, Universitätsstraße 1, 86135 Augsburg, Germany.
    Sykora, Benedikt
    Institute of Physics, University of Augsburg, Universitätsstraße 1, 86135 Augsburg, Germany.
    Grob, Stefan
    Institute of Physics, University of Augsburg, Universitätsstraße 1, 86135 Augsburg, Germany.
    Linderl, Theresa
    Institute of Physics, University of Augsburg, Universitätsstraße 1, 86135 Augsburg, Germany.
    Wilke, Andreas
    Department of Physics, Humboldt University of Berlin, Brook-Taylor-Straße 15, 12489 Berlin, Germany.
    Opitz, Andreas
    Department of Physics, Humboldt-Universität zu Berlin, 12489 Berlin, Germany.
    Hansson, Rickard
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Anselmo, Ana Sofia
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap. Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Ozawa, Yusuke
    Graduate School of Advanced Integration Science, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan.
    Nakayama, Yasuo
    Graduate School of Advanced Integration Science, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan.
    Ishii, Hisao
    Center for Frontier Science, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan and Graduate School of Advanced Integration Science, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan.
    Koch, Norbert
    Department of Physics, Humboldt University of Berlin, Brook-Taylor-Straße 15, 12489 Berlin, Germany and Helmholtz-Zentrum Berlin für Materialien und Energie GmbH - BESSY II, Albert-Einstein-Straße 15, 12489 Berlin, Germany.
    Moons, Ellen
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Schreiber, Frank
    Institute of Applied Physics, University of Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany.
    Brütting, Wolfgang
    Institute of Physics, University of Augsburg, Universitätsstraße 1, 86135 Augsburg, Germany.
    Voc from a Morphology Point of View: the Influence of Molecular Orientation on the Open Circuit Voltage of Organic Planar Heterojunction Solar Cells2014Inngår i: Journal of physical chemistry C, ISSN 1932-7455, Vol. 118, nr 46, s. 26462-26470Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The film morphology and device performance of planar heterojunction

    solar cells based on the molecular donor material α-sexithiophene (6T) are investigated.

    Planar heterojunctions of 6T with two different acceptor molecules, the C60 fullerene and

    diindenoperylene (DIP), have been prepared. The growth temperature of the 6T bottom

    layer has been varied between room temperature and 100 °C for each acceptor. By means

    of X-ray diffraction and X-ray absorption, we show that the crystallinity and the molecular

    orientation of 6T is influenced by the preparation conditions and that the 6T film

    templates the growth of the subsequent acceptor layer. These structural changes are

    accompanied by changes in the characteristic parameters of the corresponding

    photovoltaic cells. This is most prominently observed as a shift of the open circuit

    voltage (Voc): In the case of 6T/C60 heterojunctions, Voc decreases from 0.4 to 0.3 V,

    approximately, if the growth temperature of 6T is increased from room temperature to 100

    °C. By contrast, Voc increases from about 1.2 V to almost 1.4 V in the case of 6T/DIP solar

    cells under the same conditions. We attribute these changes upon substrate heating to

    increased recombination in the C60 case while an orientation dependent intermolecular coupling seems to change the origin of the photovoltaic gap in the DIP case.

  • 56.
    Inglese, Alessandro
    et al.
    Department of Micro- and Nanosciences, Aalto University, Tietotie 3, 02150 Espoo, Finland.
    Focareta, Alessia
    Department of Micro- and Nanosciences, Aalto University, Tietotie 3, 02150 Espoo, Finland.
    Schindler, Florian
    Fraunhofer Institute for Solar Energy Systems ISE, Heidenhofstraße 2, 79110 Freiburg im Breisgau, Germany.
    Schön, Jonas
    Fraunhofer Institute for Solar Energy Systems ISE, Heidenhofstraße 2, 79110 Freiburg im Breisgau, Germany.
    Lindroos, Jeanette
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Schubert, Martin C.
    Fraunhofer Institute for Solar Energy Systems ISE, Heidenhofstraße 2, 79110 Freiburg im Breisgau, Germany.
    Savin, Hele
    Department of Micro- and Nanosciences, Aalto University, Tietotie 3, 02150 Espoo, Finland.
    Light-induced degradation in multicrystalline silicon: the role of copper2016Inngår i: PROCEEDINGS OF THE 6TH INTERNATIONAL CONFERENCE ON CRYSTALLINE SILICON PHOTOVOLTAICS (SILICONPV 2016) / [ed] Ribeyron, PJ; Cuevas, A; Weeber, A; Ballif, C; Glunz, S; Poortmans, J; Brendel, R; Aberle, A; Sinton, R; Verlinden, P; Hahn, G, Elsevier, 2016, Vol. 92, s. 808-814Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this contribution, we provide an insight into the light-induced degradation of multicrystalline (mc-) silicon caused by copper contamination. Particularly we analyze the degradation kinetics of intentionally contaminated B- and Ga-doped mc-Si through spatially resolved photoluminescence (PL) imaging. Our results show that even small copper concentrations are capable of causing a strong LID effect in both B- and Ga-doped samples. Furthermore, the light intensity, the dopant and the grain quality were found to strongly impact the degradation kinetics, since faster LID was observed with stronger illumination intensity, B-doping and in the grains featuring low initial lifetime. Interestingly after degradation we also observe the formation of bright denuded zones near the edges of the B-doped grains, which might indicate the possible accumulation of copper impurities at the grain boundaries.

  • 57.
    Inglese, Alessandro
    et al.
    Aalto University.
    Lindroos, Jeanette
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik. Aalto University.
    Savin, Hele
    Aalto University.
    Accelerated light-induced degradation for detecting copper contamination in p-type silicon2015Inngår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 107, nr 5, artikkel-id 052101Artikkel i tidsskrift (Fagfellevurdert)
  • 58.
    Inglese, Alessandro
    et al.
    Department of Micro- and Nanosciences, Aalto University, Tietotie 3, 02150 Espoo, Finland.
    Lindroos, Jeanette
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Vahlman, Henri
    Department of Micro- and Nanosciences, Aalto University, Tietotie 3, 02150 Espoo, Finland.
    Savin, Hele
    Department of Micro- and Nanosciences, Aalto University, Tietotie 3, 02150 Espoo, Finland.
    Recombination activity of light-activated copper defects in p-type siliconstudied by injection- and temperature-dependent lifetime spectroscopy2016Inngår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 120, nr 12, artikkel-id 125703Artikkel i tidsskrift (Fagfellevurdert)
  • 59.
    Jackman, Henrik
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Mechanical behaviour of carbon nanostructures2014Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Abstract

    Carbon nanotubes (CNTs) have extraordinary mechanical and electrical properties. Together with their small dimensions and low density, they are attractive candidates for building blocks in future nanoelectromechanical systems and for many other applications. The extraordinary properties are however only attained by perfectly crystalline CNTs and quickly deteriorate when defects are introduced to the structure. The growth technique affects the crystallinity where in general CNTs grown by arc-discharge are close to perfectly crystalline, while CVD-grown CNTs have large defect densities. Mechanical deformation also affects these properties, even without introducing defects. When CNTs are bent they behave similarly to drinking straws, i.e. they buckle or ripple and their bending stiffness drops abruptly.

    In this thesis, the mechanical behaviour of individual CNTs and vertically aligned carbon nanofibers (VACNFs) has been studied by performing force measurements inside electron microscopes. Cantilevered CNTs, and VACNFs, were bent using a force sensor, yielding force-deflection curves while their structure was imaged simultaneously.

    We have found that CNTs grown by arc-discharge have a high enough crystallinity to possess a Young’s modulus close to the ideal value of 1 TPa. CVD-grown CNTs possess a Young’s modulus that is about one order of magnitude smaller, due to their large defect density. The VACNFs are yet another order of magnitude softer as a result of their cup-stacked internal structure.  We also found that a high defect density will increase the critical strain for the rippling onset and the relative post-rippling stiffness. Multi-walled CNTs with a small inner diameter are less prone to ripple and have a larger relative post-rippling stiffness. Our findings show large variations in the onset of rippling and the bending stiffness before and after rippling. These variations open up possibilities of tailoring the mechanical properties for specific applications.

  • 60.
    Jackman, Henrik
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för fysik och elektroteknik.
    Mechanical properties of carbon nanotubes and nanofibers2012Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Carbon nanotubes (CNTs) have extraordinary electrical and mechanical properties, and many potential applications have been proposed, ranging from nanoscale devices to reinforcement of macroscopic structures. However, due to their small sizes, characterization of their mechanical properties and deformation behaviours are major challenges. Theoretical modelling of deformation behaviours has shown that multi-walled carbon nanotubes (MWCNTs) can develop ripples in the walls on the contracted side when bent above a critical curvature. The rippling is reversible and accompanied by a reduction in the bending stiffness of the tubes. This behaviour will have implications for future nanoelectromechanical systems (NEMS). Although rippling has been thoroughly modelled there has been a lack of experimental data thus far. In this study, force measurements have been performed on individual MWCNTs and vertically aligned carbon nanofibers (VACNFs). This was accomplished by using a custom-made atomic force microscope (AFM) inside a scanning electron microscope (SEM). The measurements were done by bending free-standing MWCNTs/VACNFs with the AFM sensor in a cantilever-to-cantilever fashion, providing force-displacement curves. From such curves and the MWCNT/VACNF dimensions, measured from SEM-images, the critical strain for the very onset of rippling and the Young’s modulus, E, could be obtained. To enable accurate estimations of the nanotube diameter, we have developed a model of the SEM-image formation, such that intrinsic diameters can be retrieved. We have found an increase in the critical strain for smaller diameter tubes, a behaviour that compares well with previous theoretical modelling. VACNFs behaved very differently, as they did not display any rippling and had low bending stiffnesses due to inter-wall shear. We believe that our findings will have implications for the design of future NEMS devices that employ MWCNTs and VACNFs.

  • 61.
    Jackman, Henrik
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för fysik och elektroteknik.
    Krakhmalev, Pavel
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Svensson, Krister
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för fysik och elektroteknik.
    Direct Measurements Of Bending Stiffness And Rippling Phenomena In Free-Standing Carbon Nanotubes2011Konferansepaper (Fagfellevurdert)
  • 62.
    Jackman, Henrik
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för fysik och elektroteknik.
    Krakhmalev, Pavel
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Svensson, Krister
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för fysik och elektroteknik.
    High resolution SEM imaging of carbon nanotubes: deconvolution and retrieval of intrinsic nanotube dimensions2012Konferansepaper (Fagfellevurdert)
    Abstract [en]

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

  • 63.
    Jackman, Henrik
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för fysik och elektroteknik.
    Krakhmalev, Pavel
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Svensson, Krister
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för fysik och elektroteknik.
    Image formation mechanisms in scanning electron microscopy of carbon nanotubes,and retrieval of their intrinsic dimensions.2013Inngår i: Ultramicroscopy, ISSN 0304-3991, Vol. 124, s. 35-39Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

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

  • 64.
    Jackman, Henrik
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för fysik och elektroteknik.
    Krakhmalev, Pavel
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Svensson, Krister
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för fysik och elektroteknik.
    Large variations in the onset of rippling in concentric nanotubes.2014Inngår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 104, artikkel-id 021910Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

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

  • 65.
    Jackman, Henrik
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Krakhmalev, Pavel
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Svensson, Krister
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Mechanical beviour of carbon nanotubes in the rippled phaseManuskript (preprint) (Annet vitenskapelig)
  • 66.
    Jaczewska, Justyna
    et al.
    Institute of Physics, Jagiellonian University, Krakow, Poland.
    Budkowski, Andrzej
    M. Smoluchowski Insitute of Physics, Jagiellonian University, Reymonta 4, Krakow 30–059, Poland.
    Bernasik, Andrzej
    Faculty of Physics and Applied Computer Science, AGH-University of Science and Technology, Al. Mickiewicza 30, Krakow 30–059, Poland.
    Moons, Ellen
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för fysik och elektroteknik. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap.
    Rysz, Jakub
    M. Smoluchowski Insitute of Physics, Jagiellonian University, Reymonta 4, Krakow 30–059, Poland.
    Polymer vs Solvent Diagram of Film Structures Formed in Spin-Cast Poly(3-alkylthiophene) Blends2008Inngår i: Macromolecules, ISSN 0024-9297, E-ISSN 1520-5835, Vol. 41, s. 4802-4810Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A polymer vs solvent diagram of film structures, formed in polystyrene (PS) blends (1:1 w:w PS/PT) with poly(3-alkylthiophenes) PT [regioregular R-P3DDT, R-P3HT and regiorandom P3BT, P3DDT] spincoated onto oxidized silicon surfaces from various common solvents [p-xylene, toluene, chloroform, chlorobenzene, cyclohexanone] is presented. The structures were determined with microscopic techniques (atomic, AFM and lateral, LFM, force microscopy, fluorescent microscopy FM) and dynamic secondary ion mass spectrometry (dSIMS). The diagram, arranged according to the solubility parameter of the PTs and the solvents, exhibits three main structural classes: dewetting, lamellar, and lateral (quasi-2-dim) morphology. Decrease in PT solubility parameter δPT inhibits dewetting of polymer films. It induces also a transition from lamellar to lateral film structure. Increase in solvent solubility parameter δS has similar effects. Such behavior is related to the stability of transient homogeneous films and multilayers in the course of spin-casting. The role of δPT and δS is elucidated based on the stability analysis performed in terms of spreading coefficient (dependent on δPT) and effective interfacial tension of solvent-rich polymer phase (dependent on δS).

  • 67.
    Jansson, Anna
    et al.
    Fysik, Chalmers Tekniska Högskola.
    Nafari, Alexandra
    Sanz-Velasco, Anke
    MC2, Chalmers Tekniska Högskola.
    Svensson, Krister
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för fysik och elektroteknik.
    Gustafsson, Stefan
    Fysik, Chalmers Tekniska Högskola.
    Hermansson, Ann-Marie
    Kemi, Chalmers Tekniska Högskola.
    Olsson, Eva
    Fysik, Chalmers Tekniska Högskola.
    Novel Method for Controlled Wetting of Materials in the Environmental Scanning Electron Microscope2013Inngår i: Microscopy and Microanalysis, ISSN 1431-9276, E-ISSN 1435-8115, Vol. 19, nr 1, s. 30-7Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

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

  • 68. Janßen, Lars
    et al.
    Rinio, Markus
    Borchert, Dietmar
    Windgassen, Horst
    Bätzner, D. L.
    Kurz, H.
    Passivating thin bifacial silicon solar cells for industrial production2007Inngår i: Progress in Photovoltaics, ISSN 1062-7995, E-ISSN 1099-159X, Vol. 15, nr 6, s. 469-475Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A scheme for passivating thin multi-crystalline silicon solar cells compatible to massproduction is presented. Wafers with a thickness of 180 mm were processed into solarcells. The otherwise severe bowing has been avoided by reduced aluminium coverageon the rear surface. The process scheme includes a silicon nitride firing through stepfor conventional screen printed contacts, where a silicon nitride layer on the rearsurface acts as surface passivation layer and enables a gain in efficiency of 0.6%[abs.].

  • 69. Janßen, Lars
    et al.
    Rinio, Markus
    Borchert, Dietmar
    Windgassen, Horst
    Bätzner, D. L.
    Kurz, H.
    Thin bifacial multicrystalline silicon solar cells for industrial production2006Konferansepaper (Annet vitenskapelig)
  • 70. Janßen, Lars
    et al.
    Rinio, Markus
    Windgassen, Horst
    Nositschka, W. A.
    Borchert, Dietmar
    Kurz, H.
    Double sided silicon nitride passivated thin screen printed multicrystalline silicon solar cells2005Konferansepaper (Annet vitenskapelig)
  • 71. Joy, R. Mary
    et al.
    Gautero, L.
    Keipert-Colberg, Sinje
    Rinio, Markus
    Strola, S. A.
    Hanssen, M. S.
    van de Sanden, M. C. M.
    Borsa, D. M.
    Bosch, R. C. M.
    Fast industrial rear surface passivation dielectric stack deposition and low cost metallisation2011Konferansepaper (Annet vitenskapelig)
  • 72.
    Karlsson, Eilind
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Kitaev models for topologically ordered phases of matter2017Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    Condensed matter physics is the study of the macroscopic and microscopic properties of condensed phases of matter. For quite some time, Landau’s symmetry breaking theory was believed to describe and explain the nature of any phase transition. However, since the late 1980s, it has become apparent that it is necessary to introduce some new kind of order, named topological order, that transcends the traditional symmetry description. In this thesis we will study the Kitaev model, which is a Hamiltonian lattice model that allows one to incorporate the concept of topological order, as well as the corresponding operators and algebras. First, we consider the model on an infinite lattice, and show how to relate local and global degrees of freedom of the anyons/quasi-particles living on sites to the ribbon operators. Afterwards, we introduce holes and an external boundary to the lattice, and examine the ramifications of this generalization in terms of the ground state degeneracy. Lastly, we verify that the algebra formed by boundary site operators has the structure of a quasi-Hopf algebra. 

  • 73. Keipert, Sinje
    et al.
    Wang, P.
    Borchert, Dietmar
    Müller, S.
    Kühnemann, L.
    Rinio, Markus
    Influence of different wet chemical cleaning procedures prior to silicon nitride deposition on solar cell performance and surface passivation2008Konferansepaper (Annet vitenskapelig)
  • 74. Keipert-Colberg, Sinje
    et al.
    Ickler, B.
    Belledin, U.
    Krause, S.
    Kopfer, J. M.
    Botchak-Mouafi, Y. P.
    Kerscher, B.
    Müller, S.
    Biro, D.
    Rinio, Markus
    Borchert, Dietmar
    Investigation and development of industrial feasible cleaning sequences prior to silicon nitride deposition enhancing multicrystalline solar cell efficiency2009Konferansepaper (Annet vitenskapelig)
  • 75. Kenanoglu, Ali
    et al.
    Borchert, Dietmar
    Ballif, Christoph
    Peters, Stefan
    Zerres, Thomas
    Rinio, Markus
    Huljic, D. M.
    New large area PECVD-system for a-SiN:H deposition at 13.56 MHz2003Konferansepaper (Annet vitenskapelig)
  • 76. Kenanoglu, Ali
    et al.
    Borchert, Dietmar
    Rinio, Markus
    Abusnina, Mohammed
    Diez, S.
    Deposition of a-SiNx:H on solar cells at 13.56 MHz2004Konferansepaper (Annet vitenskapelig)
  • 77.
    Kingsvik, Kristofer
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för energi-, miljö- och byggteknik.
    Optimering av en diskmaskins värmepumpsprocess: Dimensionering av en kondensor2012Independent thesis Advanced level (professional degree), 15 poäng / 22,5 hpOppgave
  • 78.
    Kuzmenko, Volodymyr
    et al.
    Chalmers University of Technology, Gothenburg, Sweden.
    Wang, Nan
    Chalmers University of Technology, Gothenburg, Sweden.
    Haque, Mazharul
    Chalmers University of Technology, Gothenburg, Sweden.
    Naboka, Olga
    National Research Council Canada, Montreal, Canada.
    Flygare, Mattias
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Svensson, Krister
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Gatenholm, Paul
    Chalmers University of Technology, Gothenburg, Sweden.
    Liu, Johan
    Chalmers University of Technology, Gothenburg, Sweden.
    Enoksson, Peter
    Chalmers University of Technology, Gothenburg, Sweden.
    Cellulose-derived carbon nanofibers/graphene composite electrodes for powerful compact supercapacitors2017Inngår i: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 7, s. 45968-45977Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Herein, we demonstrate a unique supercapacitor composite electrode material that is originated from a sustainable cellulosic precursor via simultaneous one-step carbonization/reduction of cellulose/ graphene oxide mats at 800 C. The resulting freestanding material consists of mechanically stable carbon nanofibrous (CNF, fiber diameter 50–500 nm) scaffolds tightly intertwined with highly conductive reduced graphene oxide (rGO) sheets with a thickness of 1–3 nm. The material is mesoporous and has electrical conductivity of 49 S cm 1, attributed to the well-interconnected graphene layers. The electrochemical evaluation of the CNF/graphene composite electrodes in a supercapacitor device shows very promising volumetric values of capacitance, energy and power density (up to 46 F cm 3, 1.46 W h L 1 and 1.09 kW L 1, respectively). Moreover, the composite electrodes retain an impressive 97% of the initial capacitance over 4000 cycles. With these superior properties, the produced composite electrodes should be the “looked-for” components in compact supercapacitors used for increasingly popular portable electronics and hybrid vehicles. 

  • 79.
    Lavén, Rasmus
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Ultra-Thin Ag Films on the Sn/Si(111)-√3×√3 Surface Studied by STM2018Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The growth of atomically flat silver films on Si(111) usually requires a two-step growth, including deposition at low temperature (≈100 K) followed by slowly annealing to room temperature. In addition, flat silver films are usually only obtained on Si(111) for film thicknesses larger than the critical thickness of 6 monolayer. In this work, Ag thin film formation at ambient temperature on Sn/Si(111)-√3×√3 has been investigated experimentally using a combination of scanning tunneling microscopy, scanning tunneling spectroscopy and low-energy electron diffraction. The first buffer layer, probably consisting of both Ag and Sn, formed a partially ordered structure consisting of atomic rows which mainly followed the high-symmetry directions of the underlying Si(111) lattice. From 3 ML coverage, an atomically flat Ag film was formed. Low-energy electron diffraction confirmed that the films grew in the [111]-direction. This shows that atomically flat Ag films as thin as 3 ML can be grown on Sn/Si(111)-√3×√3 by conventional deposition at room temperature. The electronic structures of the films were studied for a range of different coverages by scanning tunneling spectroscopy. The normalized tunneling conductance showed quantum well states in the occupied electronic states, which moved towards the Fermi energy with increasing film thicknesses. 

  • 80. Lawerenz, Alexander
    et al.
    Rinio, Markus
    Riedel, Stephan
    Ghosh, Michael
    Werner, Martina
    Möller, Hans Joachim
    Measurement of the electrical activity of defects in multicrystalline silicon2000Konferansepaper (Annet vitenskapelig)
  • 81.
    Lindroos, Jeanette
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Copper-related light-induced degradation in crystalline silicon2015Doktoravhandling, med artikler (Annet vitenskapelig)
  • 82.
    Lindroos, Jeanette
    Department of Micro- and Nanosciences, Aalto University.
    Iron gettering with aluminium and back-surface passivation of single crystalline silicon2010Konferansepaper (Annet vitenskapelig)
  • 83.
    Lindroos, Jeanette
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik. Department of Micro- and Nanosciences, Aalto University.
    Boulfrad, Yacine
    Yli-Koski, Marko
    Savin, Hele
    Preventing light-induced degradation in multicrystalline silicon2014Inngår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 115, nr 15, artikkel-id 154902Artikkel i tidsskrift (Fagfellevurdert)
  • 84.
    Lindroos, Jeanette
    et al.
    Department of Micro- and Nanosciences, Aalto University.
    Fenning, David P.
    Backlund, Daniel J.
    Verlage, Erik
    Gorgulla, Angelika
    Estreicher, Stefan K.
    Savin, Hele
    Buonassisi, Tonio
    Nickel: A very fast diffuser in silicon2013Inngår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 113, nr 20, artikkel-id 204906Artikkel i tidsskrift (Fagfellevurdert)
  • 85.
    Lindroos, Jeanette
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Petter, Kai
    Hanwha Q CELLS GmbH.
    Sporleder, Kai
    Fraunhofer Center for Silicon Photovoltaics CSP.
    Turek, Marko
    Fraunhofer Center for Silicon Photovoltaics CSP.
    Pacho, Paolo
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Rinio, Markus
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Light beam induced current of light-induced degradation in high-performance multicrystalline Al-BSF cells.2017Inngår i: Proceedings of the 7th International Conference on Silicon Photovoltaics, SiliconPV 2017, 3-5 April 2017, Freiburg, Germany / [ed] Ralf Preu, Elsevier, 2017, Vol. 124, s. 99-106Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Sponge-LID decreases the Al-BSF cell efficiency by up to 10 %rel. and is only partially recoverable at 200°C. This contributionshows that Sponge-LID occurs at and near most grain boundaries, but only in the centre of the affected cell.  Furthermore,Sponge-LID is not the only type of LID in the silicon bulk. High-resolution Light Beam Induced Current mapping reveals localinternal quantum efficiency losses of up to 8 %rel. at dislocation clusters and small angle grain boundaries, which recover(nearly) fully at 200°C. Nevertheless, this dislocation-related LID appears to reduce the Al-BSF efficiency by less than 1 %rel.

  • 86.
    Lindroos, Jeanette
    et al.
    Department of Micro- and Nanosciences, Aalto University, Finland.
    Savin, Hele
    Finland.
    Formation kinetics of copper-related light-induced degradation in crystalline silicon2014Inngår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 116, nr 23, artikkel-id 234901Artikkel i tidsskrift (Fagfellevurdert)
  • 87.
    Lindroos, Jeanette
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik. Finland.
    Savin, Hele
    Department of Micro- and Nanosciences, Aalto University, Tietotie 3, 02150 Espoo, Finland.
    Review of light-induced degradation in crystalline silicon solar cells2016Inngår i: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 147, s. 115-126Artikkel, forskningsoversikt (Fagfellevurdert)
    Abstract [en]

    Although several advances have been made in the characterization and the mitigation of light-induced degradation (LID), industrial silicon solar cells still suffer from different types of light-induced efficiency losses. This review compiles four decades of LID results in both electronic- and solar-grade crystalline silicon. The review focuses on the properties and the defect models of boron-oxygen LID and copper-related LID. Current techniques for LID mitigation are presented in order to reduce cell degradation and separate copper-related LID from boron-oxygen LID. Finally, the review summarizes recent observations of severe LID in modern multicrystalline silicon solar cells.

  • 88.
    Lindroos, Jeanette
    et al.
    Department of Micro- and Nanosciences, Aalto University.
    Yli-Koski, Marko
    Haarahiltunen, Antti
    Savin, Hele
    Room-temperature method for minimizing light-induced degradation in crystalline silicon2012Inngår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 101, nr 23, artikkel-id 232108Artikkel i tidsskrift (Fagfellevurdert)
  • 89.
    Lindroos, Jeanette
    et al.
    Department of Micro- and Nanosciences, Aalto University.
    Yli-Koski, Marko
    Haarahiltunen, Antti
    Schubert, Martin C.
    Savin, Hele
    Light-induced degradation in copper-contaminated gallium-doped silicon2013Inngår i: Physica Status Solidi. Rapid Research Letters, ISSN 1862-6254, E-ISSN 1862-6270, Vol. 7, nr 4, s. 262-264Artikkel i tidsskrift (Fagfellevurdert)
  • 90. McHugo, S. A.
    et al.
    Thompson, A. C.
    Lamble, G.
    MacDowell, A.
    Celestre, R.
    Padmore, H.
    Imaizumi, M.
    Yamaguchi, M.
    Perichaud, I.
    Martinuzzi, S.
    Werner, M.
    Rinio, Markus
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    Möller, H. J.
    Sopori, B.
    Hieslmair, H.
    Flink, C.
    Istratov, A.
    Weber, E. R.
    Direct correlation of solar cell performance with metal impurity distributions in polycrystalline silicon using synchroton–based x–ray analysis1998Konferansepaper (Annet vitenskapelig)
  • 91. McHugo, S. A.
    et al.
    Thompson, A. C.
    Mohammed, A.
    Lamble, G.
    Perichaud, I.
    Martinuzzi, S.
    Werner, M.
    Rinio, Markus
    Institute for Experimental Physics, TU Bergakademie Freiberg, Silbermannstr. 1, D-09596 Freiberg, Germany .
    Koch, Wolfgang
    Hoefs, H.-U.
    Häßler, Christian
    Nanometer–scale metal precipitates in multicrystalline silicon solar cells2001Inngår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 89, nr 8, s. 4282-4288Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this study, we have utilized characterization methods to identify the nature of metal impurityprecipitates in low performance regions of multicrystalline silicon solar cells. Specifically, we haveutilized synchrotron-based x-ray fluorescence and x-ray absorption spectromicroscopy to study theelemental and chemical nature of these impurity precipitates, respectively. We have detectednanometer-scale precipitates of Fe, Cr, Ni, Cu, and Au in multicrystalline silicon materials from avariety of solar cell manufacturers. Additionally, we have obtained a direct correlation between theimpurity precipitates and regions of low light-induced current, providing direct proof that metalimpurities play a significant role in the performance of multicrystalline silicon solar cells.Furthermore, we have identified the chemical state of iron precipitates in the low-performanceregions. These results indicate that the iron precipitates are in the form of oxide or silicatecompound. These compounds are highly stable and cannot be removed with standard siliconprocessing, indicating remediation efforts via impurity removal need to be improved. Futureimprovements to multicrystalline silicon solar cell performance can be best obtained by inhibitingoxygen and metal impurity introduction as well as modifying thermal treatments during crystalgrowth to avoid oxide or silicate formation.

  • 92.
    Michels, Jasper J.
    et al.
    Holst Centre/TNO, Eindhoven, The Netherlands.
    Moons, Ellen
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Simulation of Surface-Directed Phase Separation in a Solution- Processed Polymer/PCBM Blend2013Inngår i: Macromolecules, ISSN 0024-9297, E-ISSN 1520-5835, Vol. 46, nr 21, s. 8693-8701Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The formation of the surface-induced stratified lamellar composition profile experimentally evidenced in spincoated layers of the photovoltaic donor–acceptor blend consisting of poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole]/phenyl-C61-butyric acid methyl ester (APFO-3/PCBM), as processed from chloroform, is simulated using square gradient theory extended with terms describing the interaction of the blend components with the air and substrate interfaces. The surface energy contributions have been formulated based on an enthalpic nearest-neighbor model which allows integration of common surface tension theory and experimentally accessible surface energies of the fluid phase constituents with a mean field description of a multicomponent blend confined by substrate and air interfaces. Using estimates for the quench depth and transport properties of the blend components as a function of polymer concentration, the time-resolved numerical simulations yield results that compare favorably with experimental observations, both in terms of the number of lamellae as a function of the blend layer thickness and their compositional order. The effect of blend ratio is reproduced as well, the lamellar pattern becoming more pronounced if the amount of PCBM increases relative to APFO-3.

  • 93.
    Montesdeoca-Santana, Amada
    et al.
    Universidad de La Laguna, Avda Astrofísico Fco Sánchez, 2, 38206 La Laguna, Spain.
    Jiménez-Rodríguez, E.
    González-Díaz, Benjamin
    Departamento de Física Básica, Universidad de La Laguna (ULL), Avenida Astrofísico Francisco Sánchez 2, 38206 La Laguna, S/C de Tenerife, Spain.
    Díaz-Herrera, B.
    Departamento de Física Básica, Universidad de La Laguna (ULL), Avenida Astrofísico Francisco Sánchez 2, 38206 La Laguna, S/C de Tenerife, Spain.
    Rinio, Markus
    Fraunhofer Institut für Solare Energiesysteme ISE, Laboratory and Servicecenter Gelsenkirchen, Auf der Reihe 2, 45884 Gelsenkirchen, Germany.
    Borchert, Dietmar
    Fraunhofer Institut für Solare Energiesysteme ISE, Laboratory and Servicecenter Gelsenkirchen, Auf der Reihe 2, 45884 Gelsenkirchen, Germany.
    Guerrero-Lemus, Ricardo
    Departamento de Física Básica, Universidad de La Laguna (ULL), Avenida Astrofísico Francisco Sánchez 2, 38206 La Laguna, S/C de Tenerife, Spain.
    Phosphorous gettering in acidic textured multicrystalline solar cells2011Inngår i: Physica Status Solidi. C, Current topics in solid state physics, ISSN 1610-1634, E-ISSN 1610-1642, Vol. 8, nr 3, s. 743-746Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The influence of phosphorus gettering is studied in thiswork applied to an acidic textured multicrystalline siliconsubstrate. The texturization was achieved with an HF/HNO3 solution leading to nanostructures on the silicon surface. It has been demonstrated in previous works that this textured surface decreases the reflectance on the solar cell and increases the surface area improving the photon collection and enhancing the short circuit current.

    The present study investigates the effect on the minoritycarrier lifetime of the phosphorous diffusion when it is carried out on this textured surface. The lifetime is measured by means microwave photoconductance decay and quasi steady state phototoconductance devices. The diffused textured wafers are used to fabricate solar cells and their electrical parameters are analyzed.

  • 94.
    Moons, Ellen
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för fysik och elektroteknik. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap.
    Polymer solar cells – Visualising spontaneous organisation in solution-based thin films of Polymer:fullerene blends2011Inngår i: Soft and hard materials: A symposium on surface and materials chemistry / [ed] Swedish Chemical Society, division for surface and materials chemistry, 2011Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The performance and recent improvements of polymer-based solar cells can be traced back

    to two main factors: the chemical design of new conjugated polymers and the control and

    improved understanding of morphology in these solution-processed thin films. When a thin

    film is prepared from a blend of a conjugated polymer and the fullerene-based material,

    PCBM, demixing determines the final nanostructure, which in turn is influenced by the

    polymer-fullerene interactions, the molecules’ tendency to self-organise, and the kinetics of

    the film formation. During spincoating, characterized of rapid solvent evaporation, the

    kinetics of nucleation and of two-phase separation compete. The resulting film morphology

    is important for the performance of photovoltaic devices, because, first of all, excitons need

    to diffuse to the donor/acceptor interface to separate into mobile charges, and, secondly,

    these mobile charges need to travel to the electrodes. Characterization of the structure,

    composition and molecular orientation at these interfaces and in the thin film has been one

    major challenge, because of the critical requirements of chemical contrast combined with

    lateral or depth resolution. We have used a combination of Atomic Force Microscopy

    (AFM), dynamic Secondary Ion Mass Spectrometry (d-SIMS), Near-Edge Absorption Fine

    Structure (NEXAFS) spectroscopy, and recently Neutron Reflectometry (NR), to probe the

    surface and bulk composition of polymer:fullerene blends. Differences in composition

    between surface and sub-surface are observed, and form strong evidence for vertical phase

    separation.

     

  • 95.
    Moons, Ellen
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för fysik och elektroteknik. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap.
    Spontaneous Organisation in Films of Polymer:Fullerene Blends2011Konferansepaper (Fagfellevurdert)
  • 96.
    Moons, Ellen
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för fysik och elektroteknik.
    Anselmo, Ana Sofia
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för fysik och elektroteknik. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap.
    Dzwilewski, Andrzej
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för fysik och elektroteknik.
    Svensson, Krister
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för fysik och elektroteknik.
    van Stam, Jan
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemi och biomedicinsk vetenskap.
    Vertical Phase Separation in Polymer:Fullerene Films for Photovoltaics2012Inngår i: Hybrid and Organics Photovoltaics Conference 2012: Uppsala, Sweden, 6th to 9th May 2012 / [ed] Anders Hagfeldt, Castelló, Spain: Society for Nanomolecular Photovoltaics (SEFIN) , 2012, s. 53-53Konferansepaper (Fagfellevurdert)
  • 97.
    Muntean, Stela Andrea
    Technische Universiteit Eindhoven.
    Molecular-dynamics simulations of polymeric surfaces for biomolecular applications2013Doktoravhandling, monografi (Annet vitenskapelig)
    Abstract [en]

    In-vitro diagnostics plays a very important role in the present healthcare system. It consists of a large variety of medical devices designed to diagnose a medical condition by measuring a target molecule in a sample, such as blood or urine. In vitro is the latin term for in glass and refers here to the fact that the samples are investigated outside the living organism. The range of target molecules is very broad, spanning from salts to small molecules, proteins, nucleic acids and cells. An important segment in this range is the measurement of macromolecules, such as biomarker proteins or nucleic acids, in biological samples. Biosensors are compact systems for rapid detection of biological molecules. The first commercial biosensor was introduced in 1975 for glucose analysis by the Yellow Springs Instrument Company, based on the pioneering work of Clark and Lyons. Since that time, biosensors are becoming more integrated, more sensitive, smaller, faster and cheaper and are becoming available for more and more classes of biomarkers. The immunoassays can be performed nowadays in devices with very different formats, from the high-throughput parallel analysis on well-plates to integrated point-of-care biosensors using lab-on-a-chip technology. The solid phase in these devices is very often a polymeric glass. Polymeric glasses, such as polystyrene, are easy to process and can be produced at low costs, which makes them suitable for disposable cartridges in lab-on-a-chip devices. An important process in the immunoassays is the physisorption of the macromolecules to the polymeric solid phase, such as the non-specific binding of molecules from the biological sample onto the polymeric carrier. This process plays a very important role in the limit of detection, which is given by specific binding (signal) over non-specific binding (background). Therefore, the understanding of the non-specific binding of macromolecules to polymeric surfaces is crucial for the improvement of the sensitivity in these devices. The scope of this thesis is to gain fundamental knowledge on the physisorption of proteins onto polymeric surfaces and to understand how to model this process in atomistic details. The goal of this work is to model the interaction between myoglobin and polystyrene surfaces, within a clean buffer. Computer simulations provide detailed informations about the nature of the non-specific interactions between the biomolecule and the polymeric substrate, at molecular and atomic scales. The high level of detail obtained from simulations on a smaller scale is complementary to the experimental results obtained at a larger scale. The polymeric substrate is in our case modeled by an atactic amorphous polystyrene thin film. We would like to explore the possibility of changing the properties of the polymeric substrate, to prevent non-specific interaction, by chemical modification induced by oxidation. Pure polystyrene is a hydrophobic material. We tune the hydrophilicity of its surface by adding oxygen atoms to the phenyl rings of the polystyrene chain. This addition of oxygen is a way to mimic the oxidation of polystyrene surfaces that is performed in experiments. We represent the buffer solution in simulations by explicit water molecules described at atomistic level, to which we add Na+ and Cl- ions to reproduce the salt concentration in the experimentally used buffer solution. We chose myoglobin as model biomolecule because it is a relatively small globular protein, well studied in the past and represents a good candidate for practical applications. The first question we intend to answer is to which extent the model used to represent the polystyrene chains is important for the macroscopic properties of the polystyrene films and in particular to their interaction with the water molecules. To tackle this issue, we chose two representations of the polystyrene chains: the united atoms representations on one hand, in which only the heavy atoms are modeled explicitly and the hydrogen atoms are collapsed on the carbon atoms to which they are covalently bonded, and the dummy-hydrogens atoms representation on the other hand, in which the hydrogen atoms are modeled as interaction sites with no mass and with a positive partial electrical charge. The results of these simulations are presented in Chapter 3. We begin our systematic study on the interacting species in a biomedical device by characterizing the atactic amorphous polystyrene substrate. In Chapter 4 we present the results of molecular-dynamics simulations of polystyrene surfaces with controlled degree of oxidation. The variations in degree of oxidation at the surface, ranging from 0% to 24%, correspond to different degrees of hydrophilicity of the polystyrene surface, from hydrophobic to hydrophilic. We study the influence of the oxidation on the roughness of the film, both in vacuum and in water environment. We compare our results with experimental results from AFM measurements obtained by our collaborators. We also analyze the ordering of the molecular segments in non-oxidized and oxidized polystyrene at the interface with vacuum and with water. The structure of the water interface near polystyrene surfaces with different hydrophilicity is analyzed as well. Since the interaction between proteins and polymeric surfaces is a water-mediated process, it is very important to know how water behaves near these surfaces. In Chapter 5 we discuss the dynamics of water near non-oxidized (hydrophobic) and oxidized (hydrophilic) polystyrene surfaces, both in united-atoms and dummy-hydrogen atoms representations. We discuss the orientational dynamics of water molecules and its dependence on the distance from the interface. Furthermore, the translational diffusion of water molecules is briefly discussed. In Chapter 6 we study the nature of non-specific adsorption of myoglobin, as model protein, to hydrophobic and hydrophilic polystyrene surfaces. We investigate the importance of the orientation of the protein in the process of adsorption. We also discuss the influence of the hydrophilicity of the surface on the strength of adsorption of the protein. We conclude this thesis by Chapter 7, in which our main results are summarized. In addition, we give there an outlook on further interesting questions.

  • 98.
    Muntean, Stela Andrea
    et al.
    Eindhoven University of Technology, The Netherlands.
    Lyulin, Alexey V.
    Eindhoven University of Technology, The Netherlands.
    Molecular-dynamics simulations of oxidation effects on properties of polystyrene surfaces2010Inngår i: Fifth International Conference. MMM 2010, Multiscale Materials Modeling: Conference Proceedings: Biological & Soft Materials / [ed] Peter Gumbsch, Erik van der Giessen, 2010, s. 623-626Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We study the effect of oxidation on the properties of atactic polystyrene surfaces by molecular dynamics simulations using GROMACS software package. The chemical modification of the polymeric surface changes its hydrophobic/hydrophilic character. We analyze the change in surface roughness upon oxidation and upon water presence. Additionally, we study the change in water structure near the surface as function of the hydrophilic character of the surface.

  • 99.
    Möller, Hans Joachim
    et al.
    Institute for Experimental Physics, Technische Universität Bergakademie Freiberg, Germany.
    Funke, Claudia
    Rinio, Markus
    Scholz, Sandra
    Multicrystalline silicon for solar cells2005Inngår i: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 487, nr 1-2, s. 179-187Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Crystal growth processes of multicrystalline silicon and their potential for further development are reviewed. Important parameters for theassessment of the final efficiency of the solar cells and the production yield are the bulk lifetime and the mechanical stability. The distributionand morphology of lattice defects can be related to the electrical properties. In particular oxygen in multicrystalline ingots and carbon in EFGribbons and their interaction with extended defects such as dislocations and grain boundaries will be discussed. The fracture strength dependson microcracks that are introduced through wafer slicing. The current understanding will be reviewed here.

  • 100. Möller, Hans Joachim
    et al.
    Ghosh, Michael
    Rinio, Markus
    Riedel, Stephan
    Yang, Deren
    Oxygen – Induced Microdefects in Multicrystalline Silicon1995Konferansepaper (Annet vitenskapelig)
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