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  • 99251.
    Yakimova, Rositsa
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Sublimation growth of AlN crystals: growth mode and structure evolution2005In: International Workshop on Bulk Nitride Semiconductors III,2004, 2005, p. 81-86Conference paper (Other academic)
    Abstract [en]

    Invited

  • 99252.
    Yakimova, Rositsa
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Gueorguiev Ivanov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Vines, Lasse
    University of Oslo, Norway.
    Linnarsson, Margareta K.
    KTH Royal Institute Technology, Sweden.
    Gällström, Andreas
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Giannazzo, Filippo
    CNR, Italy.
    Roccaforte, Fabrizio
    CNR, Italy.
    Wellmann, Peter
    University of Erlangen Nurnberg, Germany.
    Syväjärvi, Mikael
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Jokubavicius, Valdas
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Growth, Defects and Doping of 3C-SiC on Hexagonal Polytypes2017In: ECS Journal of Solid State Science and Technology, ISSN 2162-8769, E-ISSN 2162-8777, Vol. 6, no 10, p. P741-P745Article in journal (Refereed)
    Abstract [en]

    Technologies for the growth of 3C-SiC with crystalline quality and crystal size similar to hexagonal counterparts (6H- or 4H-SiC) are still at the laboratory stage. There are several challenges in the control of polytype stability and formation of structural defects which have to be eliminated to reveal the full potential of this material. Nevertheless, 3C-SiC has been explored for various energy, environment and biomedical applications which significantly benefit from the intrinsic semiconductor properties of this material. The future of 3C-SiC and its applications depends on the advances which will be made in improving crystalline quality, enlarging crystal size and controlling doping levels which have not been entirely explored due to the lack of high quality 3C-SiC substrates. This paper reviews recent progress in growth and doping of thick 3C-SiC layers on hexagonal SiC substrates using sublimation epitaxy. It covers the growth process on off-axis substrates and defects occurrence, as well as the issue of obtaining high resistivity material. (c) 2017 The Electrochemical Society. All rights reserved.

  • 99253.
    Yakimova, Rositsa
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Iakimov, Tihomir
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Kakanakova-Gueorguie, Anelia
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Syväjärvi, Mikael
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Jacobson, Henrik
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Virojanadara, Chariya
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Johansson, Leif
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Effect of High Temperature Annealing on Surface and Bulk Characteristics of 4H-SiC2001In: Proc. of the 43rd Electronic Material Conference, 2001Conference paper (Refereed)
  • 99254.
    Yakimova, Rositsa
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Iakimov, Tihomir
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Yazdi, Gholamreza
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Bouhafs, Chamseddine
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Eriksson, J.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Zakharov, A.
    MaxLab, Sweden .
    Boosalis, A.
    University of Nebraska, NE 68588 USA University of Nebraska, NE 68588 USA .
    Schubert, M.
    University of Nebraska, NE 68588 USA University of Nebraska, NE 68588 USA .
    Darakchieva, Vanya
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Morphological and electronic properties of epitaxial graphene on SiC2014In: Physica. B, Condensed matter, ISSN 0921-4526, E-ISSN 1873-2135, Vol. 439, p. 54-59Article in journal (Refereed)
    Abstract [en]

    We report on the structural and electronic properties of graphene grown on SiC by high-temperature sublimation. We have studied thickness uniformity of graphene grown on 4H-SiC (0 0 0 1), 6H-SiC (0 0 0 1), and 3C-SiC (1 1 1) substrates and investigated in detail graphene surface morphology and electronic properties. Differences in the thickness uniformity of the graphene layers on different SiC polytypes is related mainly to the minimization of the terrace surface energy during the step bunching process. It is also shown that a lower substrate surface roughness results in more uniform step bunching and consequently better quality of the grown graphene. We have compared the three SiC polytypes with a clear conclusion in favor of 3C-SiC. Localized lateral variations in the Fermi energy of graphene are mapped by scanning Kelvin probe microscopy It is found that the overall single-layer graphene coverage depends strongly on the surface terrace width, where a more homogeneous coverage is favored by wider terraces, It is observed that the step distance is a dominating, factor in determining the unintentional doping of graphene from the SiC substrate. Microfocal spectroscopic ellipsometry mapping of the electronic properties and thickness of epitaxial graphene on 3C-SiC (1 1 1) is also reported. Growth of one monolayer graphene is demonstrated on both Si- and C-polarity of the 3C-SiC substrates and it is shown that large area homogeneous single monolayer graphene can be achieved on the Si-face substrates. Correlations between the number of graphene monolayers on one hand and the main transition associated with an exciton enhanced van Hove singularity at similar to 4.5 eV and the free-charge carrier scattering time, on the other are established It is shown that the interface structure on the Si- and C-polarity of the 3C-SiC (1 1 1) differs and has a determining role for the thickness and electronic properties homogeneity of the epitaxial graphene.

  • 99255.
    Yakimova, Rositsa
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Ivanov, Ivan Gueorguiev
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Vines, L.
    Univ Oslo, Norway.
    Linnarsson, M. K.
    KTH Royal Inst Technol, Sweden.
    Gällström, Andreas
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Giannazzo, F.
    CNR IMM, Italy.
    Roccaforte, F.
    CNR IMM, Italy.
    Wellmann, P.
    Univ Erlangen Nurnberg, Germany.
    Syväjärvi, Mikael
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Jokubavicius, Valdas
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Growth, Defects and Doping of 3C-SiC on Hexagonal Polytypes2017In: GALLIUM NITRIDE AND SILICON CARBIDE POWER TECHNOLOGIES 7, ELECTROCHEMICAL SOC INC , 2017, Vol. 80, no 7, p. 107-115Conference paper (Refereed)
    Abstract [en]

    Technologies for the growth of 3C-SiC with crystalline quality and crystal size similar to hexagonal counterparts (6H-or 4H-SiC) are still at the laboratory stage. There are several challenges in the control of polytype stability and formation of structural defects which have to be eliminated to reveal the full potential of this material. Nevertheless, 3C-SiC has been explored for various energy, environment and biomedical applications which significantly benefit from the intrinsic semiconductor properties of this material. The future of 3C-SiC and its applications depends on the advances which will be made in improving crystalline quality, enlarging crystal size and controlling doping levels which have not been entirely explored due to the lack of high quality 3C-SiC substrates. This paper reviews recent progress in growth and doping of thick 3C-SiC layers on hexagonal SiC substrates using sublimation epitaxy. It covers the growth process on off-axis substrates and defects occurrence, as well as the issue of obtaining high resistivity material.

  • 99256.
    Yakimova, Rositsa
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Jacobson, H
    Syväjärvi, Mikael
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Kakanakova-Georgieva, Anelia
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Iakimov, Tihomir
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Virojanadara, Chariya
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Johansson, Leif
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Janzén, Erik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Impact of the initial surface conditions on defect appearance in 4H-SiC epilayers2002In: Materials Science Forum, Vols. 389-393, 2002, Vol. 389-3, p. 283-286Conference paper (Refereed)
    Abstract [en]

    Effect of surface irregularities on defect nucleation and development in thick epitaxial layers of 4H-SiC has been investigated. It has been shown that during growth extended defects may undergo transformation and thus stacking faults can be formed, which is favored in thicker layers (e.g. 50mum). Network of misfit dislocations appears if the initial surface has a certain critical roughness and a lower surface energy. Evidence has been presented that well ordered graphite layer might form on the substrates during the preheating stage prior to growth via sublimation.

  • 99257.
    Yakimova, Rositsa
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Current status and advances in the growth of SiC2000In: Diam. Relat. Mater., Vol. 9, Science Direct , 2000, Vol. 9, no 3, p. 432-438Conference paper (Refereed)
    Abstract [en]

    Recent achievements in crystal growth and homoepitaxy of SiC, mainly of the 4H polytype, have been discussed. Several growth techniques, such as seeded sublimation growth, high temperature chemical vapor deposition, sublimation epitaxy and liquid phase epitaxy have been utilized to develop technological procedures and understand the growth processes better. The advantages of either method have been stressed. The main target has been the reproducible growth of micropipe free substrate material and thick epitaxial layers for device applications. The purity of the layers has been of special interest. The results obtained are indicative for the massive progress that has been achieved in SiC crystal growth during recent years.

  • 99258.
    Yakimova, Rositsa
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Kakanakova-Georgieva, Anelia
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Yazdi, Gholamreza R.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Gueorguiev, Gueorgui K.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Syväjärvi, Mikael
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Sublimation growth of AlN crystals: Growth mode and structure evolution2005In: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 281, no 1, p. 81-86Article in journal (Refereed)
    Abstract [en]

    The aim of this study has been to realize growth conditions suitable for seeded sublimation growth of AlN and to understand the relationship between external growth parameters and the initial stages of growth with respect to growth mode and structure evolution. Close space sublimation growth geometry has been used in a RF-heated furnace employing high-purity graphite coated by TaC with a possibility to change the growth environment from C- to Ta-rich. Influence of certain impurities on the initially formed crystallites with respect to their shape, size and population has been considered. It is shown that some impurity containing vapor molecules may act as transport agents and suppliers of nitrogen for the AlN growth. SiC seeds, both bare and with MOCVD AlN buffer, have been employed. By varying the process conditions we have grown crystals with different habits, e.g. from needles, columnar- and plate-like, to freestanding quasi-bulk material. The growth temperature ranged 1600–2000 °C whereas the optimal external nitrogen pressure varied from 200 to 700 mbar. There is a narrow parameter window in the relationship temperature–pressure for the evolution of different structural forms. Growth modes with respect to process conditions are discussed.

  • 99259.
    Yakimova, Rositsa
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Lebedev, A.A.
    Ivanov, A.M.
    Strokan, N.B.
    Syväjärvi, Mikael
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    The limit of SiC detector energy resolution in ions spectrometry2006In: Materials Science Forum, Vols. 527-529, 2006, Vol. 527-529, p. 1477-1480Conference paper (Refereed)
  • 99260.
    Yakimova, Rositsa
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Monemar, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Preface2007In: First International Symposium on Growth of Nitrides ISGN-1,2006, Journal of Crystal Growth, Vol. 300: Elsevier Science , 2007Conference paper (Refereed)
  • 99261.
    Yakimova, Rositsa
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Petoral, Rodrigo Jr
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, Faculty of Science & Engineering.
    Yazdi, Gholamreza
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Vahlberg, Cecilia
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, Faculty of Science & Engineering.
    Lloyd Spetz, Anita
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics.
    Uvdal, Kajsa
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, Faculty of Science & Engineering.
    Surface functionalization and biomedical applications based on SiC2007In: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 40, no 20, p. 6435-6442Article in journal (Refereed)
    Abstract [en]

    The search for materials and systems, capable of operating long term under physiological conditions, has been a strategy for many research groups during the past years. Silicon carbide (SiC) is a material, which can meet the demands due to its high biocompatibility, high inertness to biological tissues and to aggressive environment, and the possibility to make all types of electronic devices. This paper reviews progress in biomedical and biosensor related research on SiC. For example, less biofouling and platelet aggregation when exposed to blood is taken advantage of in a variety of medical implantable materials while the robust semiconducting properties can be explored in surface functionalized bioelectronic devices. © 2007 IOP Publishing Ltd.

  • 99262.
    Yakimova, Rositsa
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Steinhoff, Georg
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Petoral, Rodrigo Jr
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, Faculty of Science & Engineering.
    Vahlberg, Cecilia
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, Faculty of Science & Engineering.
    Khranovskyy, Volodymyr
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Yazdi, Gholamreza
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Uvdal, Kajsa
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, Faculty of Science & Engineering.
    Lloyd Spetz, Anita
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics.
    Novel material concepts of transducers for chemical and biosensors2007In: Biosensors & bioelectronics, ISSN 0956-5663, E-ISSN 1873-4235, Vol. 22, no 12, p. 2780-2785Article in journal (Refereed)
    Abstract [en]

    The objectives of this work are to contribute to the knowledge about physical and chemical properties of WBG semiconductors, such as ZnO and GaN towards development of advanced bio- and chemical sensors. For the semiconductors, growth techniques typically yielding single crystal material are applied. Thin epitaxial quality films of ZnO and GaN are fabricated on SiC or sapphire substrates. An emphasis is given to ZnO due to the interesting combination of the semiconductor and oxide properties. Surface bio-functionalization of ZnO is performed by APTES, MPA or MP-TMS molecules. We have compared some of the results to (hydroxylated) GaN surfaces functionalized by MP-TMS. The covalent attachment of the self-assembled biomolecular layers has been proven by XPS analysis. For complementary electrical characterization impedance spectroscopy measurements were performed. The results are intended to serve the realization of bioelectronic transducer devices based on SiC or GaN transistors with a ZnO gate layer. To take advantage of the catalytic properties of ZnO, initial prototypes of chemical sensors for gas sensing are processed on ZnO deposited either on SiC or on sapphire and they are further tested for the response to reducing or oxidizing gas ambient. The sensor devices show sensitivity to oxygen in the surface resistivity mode while a Pt Schottky contact ZnO/SiC device responds to reducing gases. These results are compared to published results on Pt/GaN Schottky diodes. © 2007 Elsevier B.V. All rights reserved.

  • 99263.
    Yakimova, Rositsa
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Syväjärvi, Mikael
    Linköping University, Department of Physics, Chemistry and Biology.
    Advances in SiC thick epilayer growth for power devices and sensors2005In: WASMPE 2005,2005, 2005, p. 26-28Conference paper (Refereed)
  • 99264.
    Yakimova, Rositsa
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Syväjärvi, Mikael
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Liquid Phase Epitaxy of SiC2007In: Liquid Phase Epitaxy of Electronic, Optical and Optoelectronic Materials / [ed] Peter Capper, Michael Mauk, UK: Wiley , 2007, 1, p. 179-202Chapter in book (Other academic)
    Abstract [en]

      Liquid-Phase Epitaxy (LPE) is a technique used in the bulk growth of crystals, typically in semiconductor manufacturing, whereby the crystal is grown from a rich solution of the semiconductor onto a substrate in layers, each of which is formed by supersaturation or cooling. At least 50% of growth in the optoelectronics area is currently focussed on LPE.

    This book covers the bulk growth of semiconductors, i.e. silicon, gallium arsenide, cadmium mercury telluride, indium phosphide, indium antimonide, gallium nitride, cadmium zinc telluride, a range of wide-bandgap II-VI compounds, diamond and silicon carbide, and a wide range of oxides/fluorides (including sapphire and quartz) that are used in many industrial applications. A separate chapter is devoted to the fascinating field of growth in various forms of microgravity, an activity that is approximately 30-years old and which has revealed many interesting features, some of which have been very surprising to experimenters and theoreticians alike.

    • Covers the most important materials within the field
    • The contributors come from a wide variety of countries and include both academics and industrialists, to give a balanced treatment
    • Builds-on an established series known in the community
    • Highly pertinent to current and future developments in telecommunications and computer-processing industries.
  • 99265.
    Yakimova, Rositsa
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Syväjärvi, Mikael
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Ciechonski, Rafal
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Wahab, Qamar Ul
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Growth of device quality 4H-SiC by high velocity epitaxy2004In: Materials Science Forum, Vols. 457-460, 2004, Vol. 457-460, p. 201-204Conference paper (Refereed)
    Abstract [en]

    Thick (>20 μm) 4H-SiC layers in doping range of low 1015-1016 cm-3 were grown by sublimation epitaxy at a growth rate of similar to50 mum/hour. Two inch 25 μm thick layers were fabricated with standard thickness deviation of 3.77%. Effect of important process parameters on the material grade has been discussed. The Schottky diodes processed on this material sustained 900V reverse voltage at a current of 1.7 x 10-8 A, while measured on MOS capacitors the interface state density was as low as similar to6-9 x 1010 cm-2.

  • 99266.
    Yakimova, Rositsa
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Syväjärvi, Mikael
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Iakimov, Tihomir
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Jacobsson, Henrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Kakanakova-Georgieva, Anelia
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Raback, P.
    Råback, P., Center for Scientific Computing, P.O. Box 405, FIN-02101 Espoo, Finland.
    Janzén, Erik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Growth of silicon carbide: Process-related defects2001In: Appl. Surf. Sci., Vol. 184, 2001, Vol. 184, no 1-4, p. 27-36Conference paper (Refereed)
    Abstract [en]

    This paper reviews the present understanding of defect formation and development in relation to process conditions in 4H-SiC crystal growth and epitaxy. The polytype uniformity during seeded sublimation growth of SiC boules has been discussed. Insight into different structural imperfections has been attempted. The role of the temperature distribution, as well as of the quality of seed/crystal interface in the occurrence of grown-in defects has been demonstrated. Micropipe termination by liquid-phase deposition along with defect evolution in subsequently grown layers due to rough interface has been addressed. Finally, a relation between extended morphological defects in thick (50-100 µm) 4H-SiC epitaxial layers and local stress in the material has been suggested. Optimised growth conditions to reduce the overall defect density have been proposed. © 2001 Elsevier Science B.V. All rights reserved.

  • 99267.
    Yakimova, Rositsa
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Syväjärvi, Mikael
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Iakimov, Tihomir
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Jacobsson, Henrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Raback, R
    Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden Okmet AB, S-17824 Ekero, Sweden Ctr Comp Sci, FIN-02101 Espoo, Finland Okmet Ltd, FIN-01301 Vantaa, Finland.
    Vehanen, A
    Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden Okmet AB, S-17824 Ekero, Sweden Ctr Comp Sci, FIN-02101 Espoo, Finland Okmet Ltd, FIN-01301 Vantaa, Finland.
    Janzén, Erik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Polytype stability in seeded sublimation growth of 4H-SiC boules2000In: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 217, no 3, p. 255-262Article in journal (Refereed)
    Abstract [en]

    Process conditions for stable single polytype growth of 4H-SiC boules via a seeded sublimation technique have been developed. Reproducible results can be obtained in a narrow temperature interval around 2350 degrees C and on the C-face of 4H-SiC seeds. Evidence is presented that during the initial stage of growth, morphological instabilities may occur resulting in structural defects. A solution is proposed based on the experimental findings, i.e. the first regions of growth ought to be carried out at a low supersaturation (growth rate similar to 100 mu m/h) until a proper growth front has developed. (C) 2000 Elsevier Science B.V. All rights reserved.

  • 99268.
    Yakimova, Rositsa
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Syväjärvi, Mikael
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Iakimov, Tihomir
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Okunev, AO
    Udal'tsov, VE
    Janzén, Erik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Orientation-dependent defect formation in silicon carbide epitaxial layers2003In: Materials Science Forum, Vols. 433-436, 2003, Vol. 433-4, p. 281-284Conference paper (Refereed)
    Abstract [en]

    Thick SiC epitaxial layers have been grown by sublimation on different initial surfaces in the range of 1800-2200degreesC. Evidences have been obtained that independently of the polytype and the surface polarity, there exists a transition region between the substrate and the epilayer in which the crystal structure is highly disturbed either by formation of misfit dislocations, predominantly in growth on vicinal (off-axis) surfaces or by domain boundaries and polytype transformation during growth on atomically flat (on-axis) surfaces. The transition layer thickness may vary from 15 to 50 mum and it seems to depend on the growth rate.

  • 99269.
    Yakimova, Rositsa
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Syväjärvi, Mikael
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Jacobson, Henrik
    Linköping University, Department of Social and Welfare Studies. Linköping University, Faculty of Educational Sciences.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Some aspects of extended defects formation and their reduction in silicon carbide crystals2003In: Recent research developments in materials science & engineering. Vol. 1, pt. 1 / [ed] S. G. Pandalai, Kerala, India: Trans Research Network , 2003, 1, p. 619-646Chapter in book (Other academic)
  • 99270.
    Yakimova, Rositsa
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Syväjärvi, Mikael
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Jacobsson, H
    Kakanakova-Georgieva, Anelia
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Rendakova, S
    Dmitriev, V
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Defect evolution in SiC sublimation epitaxy layers grown on LPE buffers with reduced micropipe density2001In: Materials Research Society Symposium Proceedings, Vol. 640, 2001, p. H2.1.1-H2.1.6Conference paper (Refereed)
  • 99271.
    Yakimova, Rositsa
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Syväjärvi, Mikael
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Kakanakova-Georgieva, Anelia
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Janzén, Erik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Stress related morphological defects in SiC epitaxial layers2001In: Diam. Relat. Mater., Vol. 10, 2001, Vol. 10, no 3-7, p. 1246-1250Conference paper (Refereed)
    Abstract [en]

    Morphological defects have been studied on thick 4H-SiC layers being grown with high growth rate (100 µm/h) by sublimation epitaxy. While the surface morphology of such layers is generally specular and featureless, extended defects are observed to emanate from some obstacles. The length of the defects can vary between 60 and 950 µm and the defect can occur at different stages of growth. Evidence shows that these defects occur due to localised stress present during the epitaxial growth. The causes for the defects can be greatly reduced by improving the structural quality of the substrate material. © 2001 Elsevier Science B.V. All rights reserved.

  • 99272.
    Yakimova, Rositsa
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Syväjärvi, Mikael
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Pons, M.
    Institut National Polytechnique de Grenoble.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Influence of gravity on defect formation in homoepitaxial layers of SiC grown by sublimation2001In: ESA SP-454, 2001, p. 381-Conference paper (Refereed)
    Abstract [en]

    4H-SiC homoepitaxial growth has been performed by sublimation process. The basic transport mechanism and dynamics of the growth has been studied. Both, experiment and numerical modelling have been performed. It has been shown that high growth rate (0.1 mm/hour) can be obtained when the overall structural quality is very good and the surface morphology is excellent. However, deep level defects associated with impurities have been observed. Evidence has been obtained that the impurity incorporation may be influenced by gravity-induced growth instabilities. At this stage, numerical modelling of the growth process has been performed considering only macroscopic features. For the present experimental configuration, preliminary results reveal that the influence of microgravity is low. The macroscopic transfer phenomena leading to the growth of the crystal are mainly diffusive. The future is to design specific experiments involving higher temperature difference between source and seed, as well as to consider microscopic growth phenomena.

  • 99273.
    Yakimova, Rositsa
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Syväjärvi, Mikael
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Rendakova, S
    Linkoping Univ, Dept Phys & Measurement Technol, SE-58183 Linkoping, Sweden TDI Inc, Gaithersburg, MD 20877 USA Howard Univ, MSRCE, Washington, DC 20059 USA.
    Dimitriev, VA
    Linkoping Univ, Dept Phys & Measurement Technol, SE-58183 Linkoping, Sweden TDI Inc, Gaithersburg, MD 20877 USA Howard Univ, MSRCE, Washington, DC 20059 USA.
    Henry, Anne
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Janzén, Erik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Micropipe healing in liquid phase epitaxial growth of SiC2000In: Materials Science Forum, Vols. 338-342, Trans Tech Publications Inc., 2000, Vol. 338-3, p. 237-240Conference paper (Refereed)
    Abstract [en]

    In this study we demonstrate the feasibility of micropipe reduction in SiC commercial wafers by using liquid phase epitaxial (LPE) growth. We have studied the stability of the micropipe healing by performing hot KOH etching and growing thick (40-50 mum) layer with sublimation epitaxy at temperature higher than that used for the LPE growth. Experimental evidences have been collected by means of different techniques and a phenomenological model for micropipe healing is proposed.

  • 99274.
    Yakimova, Rositsa
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Vasiliauskas, Remigijus
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Eriksson, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, The Institute of Technology.
    Syväjärvi, Mikael
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Progress in 3C-SiC growth and novel applications2012In: Materials Science Forum Vol 711, Trans Tech Publications Inc., 2012, Vol. 711, p. 3-10Conference paper (Refereed)
    Abstract [en]

    Recent research efforts in growth of 3C-SiC are reviewed. Sublimation growth is addressed with an emphasis on the enhanced understanding of polytype stability in relation to growth conditions, such as supersaturation and Si/C ratio. It is shown that at low temperature/supersaturation spiral 6H-SiC growth is favored, which prepares the surface for 3C-SiC nucleation. Provided the supersaturation is high enough, 3C-SiC nucleates as two-dimensional islands on terraces of the homoepitaxial 6H-SiC. Effect of different substrate surface preparations is considered. Typical extended defects and their electrical activity is discussed. Finally, possible novel applications are outlined.

  • 99275.
    Yakimova, Rositsa
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Virojanadara, Chariya
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Gogova, Daniela
    Leibniz Institute for Crystal Growth, Berlin, Germany.
    Syväjärvi, Mikael
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Siche, D.
    Leibniz Institute for Crystal Growth, Berlin, Germany.
    Larsson, Krister
    Department of Materials Chemistry, Uppsala University, Uppsala, Sweden.
    Johansson, Leif
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Analysis of the Formation Conditions for Large Area Epitaxial Graphene on SiC Substrates2010In: SILICON CARBIDE AND RELATED MATERIALS 2009, PTS 1 AND 2 / [ed] Bauer, AJ; Friedrichs, P; Krieger, M; Pensl, G; Rupp, R; Seyller, T, Trans Tech Publications Inc., 2010, Vol. 645-648, p. 565-568Conference paper (Refereed)
    Abstract [en]

    We are aiming at understanding the graphene formation mechanism on different SiC polytypes (6H, 4H and 3C) and orientations with the ultimate goal to fabricate large area graphene (up to 2 inch) with controlled number of monolayers and spatial uniformity. To reach the objectives we are using high-temperature atmospheric pressure sublimation process in an inductively heated furnace. The epitaxial graphene is characterized by ARPES, LEEM and Raman spectroscopy. Theoretical studies are employed to get better insight of graphene patterns and stability. Reproducible results of single layer graphene on the Si-face of 6H and 4H-SiC polytypes have been attained. It is demonstrated that thickness uniformity of graphene is very sensitive to the substrate miscut.

  • 99276.
    Yakimova, Rositsa
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Vouroutzis, N
    Syväjärvi, Mikael
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Stoemenos, J
    Morphological features related to micropipe closing in 4H-SiC2005In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 98, no 3, p. 34905-Article in journal (Refereed)
    Abstract [en]

    The closing of micropipes during sublimation epitaxy has been studied. Shallow trenches are formed along the direction of the step-flow growth in the vicinity of closed micropipes. The trenches are related to a serious disturbance of the flowing steps and the formation of stacking faults in the (0001) basal plane as well as in the (1 1- 00) plane. A micropipe closes when the speed of the growth steps is higher than the spiral growth around the micropipe. This mechanism is related to a bending of the micropipe along the trench and the progressive emission of elementary screw dislocations along the trench. The morphology of the disturbed steps at the trenches and the related defects have been studied by transmission electron microscopy and atomic force microscopy. Supporting evidences are presented with optical micrographs from etched epilayers. Image forces, which are developed by the growth steps, stabilize the bending of the micropipes. The limitation of the bending is also discussed. © 2005 American Institute of Physics.

  • 99277.
    Yakimova, Rositsa
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Yazdi, Gholam Reza
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Nguyen, Son Tien
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Ivanov, Ivan Gueorguiev
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Syväjärvi, Mikael
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Sun, S.
    Tompa, G.
    Kuznetsov, A.
    Svensson, B.
    Optical and Morphological Features of Bulk and Homoepitaxial ZnO2006In: Superlattices and Microstructures, ISSN 0749-6036, E-ISSN 1096-3677, Vol. 39, p. 247-256Article in journal (Refereed)
    Abstract [en]

    ZnO substrate crystals from two different sources, and epitaxial layers have been studied by SEM, AFM, photoluminescence (T=2-135K) and EPR. Although fabricated by the same growth principle, i.e. the hydrothermal technique, the substrates differ in terms of purity and structural quality. In the PL spectra of all samples the dominating emission originates from the donor bound exciton (BE) recombination positioned at about 3361 meV. The temperature dependence of the spectra confirms the assignment of the free exciton emission in the purest sample, the line at 3376 meV evolves into a broad peak at higher temperatures, probably including both A and B excitons. Another FE-related emission appears as a shoulder on the high-energy side of FEA,B above 40 K. It is expected and associated with the crystal-field split-off counterpart of the valence band. Free-exciton related emission in the less pure sample can only be seen if the temperature is above 45 K. At T=135K all bound excitons are quenched and the spectrum in both samples consists of the free exciton no-phonon lines and their replicas. However, the emission from the pure samples is several orders of magnitude stronger than that from the other sample, which indicates strong non-radiative quenching of the excitons in the latter sample. The EPR measurements reveal a possible scenario of impurity re-arrangement, e.g. annealing at 950 °C may dissociate existing complexes and release Fe as isolated ions. The AFM and SEM investigations of an epilayer grown by MOCVD on one of the studied substrates have indicated growth instabilities and structural irregularities, thus pointing to the need for substrate quality and epitaxial process optimization.

  • 99278.
    Yakimova, Rositsa
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Yazdi, Gholam Reza
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Sritirawisarn, N.
    Syväjärvi, Mikael
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Structure Evolution of 3C-SiC on Cubic and Hexagonal Substrates2006In: Materials Science Forum, Vols. 527-529, 2006, Vol. 527-529, p. 283-286Conference paper (Refereed)
  • 99279.
    Yakimova, Rositsa
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Yazdi, Gholamreza
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Iakimov, Tihomir
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Eriksson, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Applied Sensor Science. Linköping University, Faculty of Science & Engineering.
    Darakchieva, Vanya
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Challenges of Graphene Growth on Silicon Carbide2013In: ECS Transactions, Vol. 53, no 1, p. 9-16Article in journal (Refereed)
    Abstract [en]

    One of the main challenges in the fabrication of device quality graphene is the achievement of large area monolayer graphene that is processing compatible. Here, the impact of the substrate properties on the thickness uniformity and electronic characteristics for epitaxial graphene on SiC produced by high temperature sublimation has been evidenced and discussed. Several powerful techniques have been used to collect data, among them large scale ellipsometry mapping has been demonstrated for the first time. The study is covering all three SiC polytype, e.g. 4H-, 6H- and 3C-SiC in order to reveal eventual peculiarities that have to be controlled during graphene growth. The advantage of the cubic polytype is unambiguously demonstrated.

  • 99280.
    Yakimova, Rositza
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Selegård, Linnea
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, The Institute of Technology.
    Khranovskyy, Volodymyr
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Pearce, Ruth
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Lloyd Spetz, Anita
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Uvdal, Kajsa
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, Faculty of Science & Engineering.
    ZnO materials and surface tailoring for biosensing2012In: Frontiers in bioscience (Elite edition), ISSN 1945-0508, Vol. 4, no 1, p. 254-278Article in journal (Refereed)
    Abstract [en]

    ZnO nanostructured materials, such as films and nanoparticles, could provide a suitable platform for development of high performance biosensors due to their unique fundamental material properties. This paper reviews different preparation techniques of ZnO nanocrystals and material issues like wettability, biocompatibility and toxicity, which have an important relevance to biosensor functionality. Efforts are made to summarize and analyze existing results regarding surface modification and molecular attachments for successful biofunctionalization and understanding of the mechanisms involved. A section is devoted to implementations of tailored surfaces in biosensors. We end with conclusions on the feasibility of using ZnO nanocrystals for biosensing.

  • 99281.
    Yakob, Ramsin
    Linköping University, Department of Management and Engineering, Business Administration. Linköping University, Faculty of Arts and Sciences.
    Intelligence of Solution Search:Linking errors back to problems2011Conference paper (Refereed)
    Abstract [en]

    This paper investigates the iterative process between analytical-and directional solutionsearch modes in complex problem-solving. It aims to contribute to the growing stream of researchthat focuses on the evolution of solution search strategies that underlie the unfolding ofknowledge-intensive activities in projects. The theoretical departure is the distinction betweenanalytical and directional reasoning in solution search. Empirical material is collected from aqualitative-case study of design engineering activities in a platform development project at VolvoCar Corporation. Personal interviews, project documentation and observations are used to establishconstruct and internal validity of findings. Results show that the search for solutions to complexobstacles is more than a monotonic process of representing action-outcome linkages andsubsequently exploring such beliefs. Synthesized search is discussed as an important mechanismfor reducing knowledge gaps between errors and their underlying problems, and the subsequentdiscrepance between believed action-outcome linkages. Results are presented through a dynamicsolution search model illuminating the relationship between three different forms of solutionsearch modes: analytical-, directional- and synthesized search.

  • 99282.
    Yakob, Ramsin
    Linköping University, Department of Management and Engineering, Business Administration . Linköping University, Faculty of Arts and Sciences.
    The Problem with Errors: Solution Search in Platform Development2009Doctoral thesis, monograph (Other academic)
    Abstract [en]

    This dissertation is concerned with problem-solving in platform development. A problem isconceived of as an obstacle that needs to be overcome in order to reach a desired outcome,whereas a solution is denoted by the set of activities required to reach such an outcome. Aplatform is conceived of as the technological foundation made up of a number of elements thatare purposely planned and developed to form a common structure from which a stream ofderivative products can be developed. Problem-solving in platform development is a non-trivialtask since platforms need to cater for both commonality and distinctiveness across a number ofderivative products. Further, several design architectures are intertwined in the development ofplatforms, giving rise to increased complexity. The purpose of this dissertation is to exploreplatform development from a problem-solving perspective, with the purpose of answering whatproblem-solving activities are carried out in platform development processes, how are differentapproaches to the search for solutions related to problem-solving in platform development, andhow can problem-solving in platform development be conceptualized? This dissertation is basedon two empirical studies of platform development processes from the telecommunication andautomotive industry, and draws upon a qualitative research methodology. The result of this studyis an iterative and dynamic model of solution search in problem-solving. This dissertationimplies a distinction between problems and errors in platform development. Solution searchemerge as a matter of choice of whether to engage in problem-solving activities and/or errorcorrection activities during the development of platforms. Solution search also surface as anintermingled process of search for required inputs, outputs, or governing laws (i.e. solutions) forreaching a desired goal. In this process, analytical search, directional search, and synthesizedsearch and the facilitation and management of both feed-back and feedforward is important.

  • 99283.
    Yakob, Ramsin
    et al.
    Linköping University, Department of Management and Engineering, Business Administration. Linköping University, Faculty of Arts and Sciences.
    Bengtsson, Marie
    Linköping University, Department of Management and Engineering, Business Administration. Linköping University, Faculty of Arts and Sciences.
    Wahlstedt, Linnéa
    Linköping University, Department of Management and Engineering, Business Administration. Linköping University, Faculty of Arts and Sciences.
    Att Styra Problemlösning2012In: Styrning: med projekt och kunskap i fokus / [ed] Söderlund, Jonas & Tell, Fredrik, Lund: Studentlitteratur, 2012, p. 225-244Chapter in book (Other academic)
  • 99284.
    Yakob, Ramsin
    et al.
    Linköping University, Faculty of Arts and Sciences. Linköping University, Department of Management and Engineering.
    Tell, Fredrik
    Linköping University, Faculty of Arts and Sciences. Linköping University, Department of Management and Engineering, Business Administration .
    Decomposing and Recomposing - On Anatomies and Integration2007In: International Continuous Innovation Network CINet Conference,2007, 2007Conference paper (Refereed)
    Abstract [en]

      

  • 99285.
    Yakob, Ramsin
    et al.
    Linköping University, Faculty of Arts and Sciences. Linköping University, Department of Management and Engineering.
    Tell, Fredrik
    Linköping University, Faculty of Arts and Sciences. Linköping University, Department of Management and Engineering, Business Administration .
    Decomposing and Recomposing - On Anatomies and Integration. A case study of a platform development project in the Telecom Industry2007In: the International Research Network on Organizing by Projects IRNOP Conference,2007, 2007Conference paper (Refereed)
  • 99286.
    Yakob, Ramsin
    et al.
    Linköping University, Department of Management and Engineering, Business Administration. Linköping University, Faculty of Arts and Sciences.
    Tell, Fredrik
    Linköping University, Department of Management and Engineering, Business Administration. Linköping University, Faculty of Arts and Sciences.
    Detecting Errors Early: Management of problem-solving in product platform projects2009In: Platforms, Markets and Innovation / [ed] Annabelle Gawer, Cheltenham and Northampton: Edward Elgar , 2009, 1, p. 416-Chapter in book (Other academic)
    Abstract [en]

    'Annabelle Gawer's Platforms, Markets and Innovation is the first serious exploration of the critical but subtle role that platforms play in business, society and our personal lives. As digital technologies penetrate every nook and cranny of the world around us, we rely on platforms to both help us use the new technologies, as well as to organize new markets of innovation that add applications on top of the platforms and make them far more valuable. Dr Gawer's excellent book is designed to help us understand the mysterious nature of platforms. It brings together the insights of twenty-four experts around the world who contributed to the fourteen chapters of the book. Dr Gawer's book is invaluable to anyone trying to understand the nuanced nature of platforms, and their implications for the evolution of innovation in the 21st century.'- Irving Wladawsky-Berger, IBM Academy of Technology, US

    The emergence of platforms is a novel phenomenon impacting most industries, from products to services. Industry platforms such as Microsoft Windows or Google, embedded within industrial ecosystems, have redesigned our industrial landscapes, upset the balance of power between firms, fostered innovation and raised new questions on competition and innovation.

    Annabelle Gawer presents cutting-edge contributions from 24 top international scholars from 19 universities across Europe, the USA and Asia, from the disciplines of strategy, economics, innovation, organization studies and knowledge management. The novel insights assembled in this volume constitute a fundamental step towards an empirically based, nuanced understanding of the nature of platforms and the implications they hold for the evolution of industrial innovation. The book provides an overview of platforms and discusses governance, management, design and knowledge issues.

    With a multidisciplinary approach, this book will strongly appeal to academics and advanced students in management, innovation, strategy, economics and design. It will also prove an enlightening read for business managers in IT industries.

    Contributors: C.Y. Baldwin, K.J. Boudreau, S. Brusoni, M.A. Cusumano, T.R. Eisenmann, D.S. Evans, T.

  • 99287.
    Yakob, Ramsin
    et al.
    Linköping University, Faculty of Arts and Sciences. Linköping University, Department of Management and Engineering, Business Administration .
    Tell, Fredrik
    Linköping University, Faculty of Arts and Sciences. Linköping University, Department of Management and Engineering, Business Administration .
    Managing near decomposability in complex platform development projects2007In: International Journal of Technology Intelligence and Planning, ISSN 1740-2832, Vol. 3, no 4, p. 387-407Article in journal (Refereed)
    Abstract [en]

    Product Platforms are understood as the sharing of common and underlying technological assets from which a number of derivative products can be produced. The large number and character of technological interdependences give rise to system complexities, implying that product platforms can be managed as nearly decomposable system. We study the managerial implications of such complexity in a telecommunications platform enhancement project. We find that managing near decomposability requires the ability to provide feed-back and feed-forward information, relating to the implementation and planning activities of such a project and that this required output can be provided through the process of aggregation. © 2007, Inderscience Publishers.

  • 99288.
    Yakob, Ramsin
    et al.
    Linköping University, Faculty of Arts and Sciences. Linköping University, Department of Management and Engineering.
    Tell, Fredrik
    Linköping University, Faculty of Arts and Sciences. Linköping University, Department of Management and Engineering, Business Administration .
    Managing Near Decomposability in Complex Platform Development Projects2007In: the RD Management Conference,2007, 2007Conference paper (Refereed)
  • 99289.
    Yakymenko Alkaissi, Lina
    Linköping University, Department of Clinical and Experimental Medicine, Division of Surgery, Orthopedics and Oncology. Linköping University, Faculty of Medicine and Health Sciences.
    Bacterial epithelial interaction in intestinal inflammation2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The intestine is constantly exposed to bacteria, invading viruses and ingested food. The intestinal barrier serves as a gate preventing passage of harmful components, and at the same time maintaining absorption of nutrients and water. There are over 300 different bacteria species in the human gastrointestinal tract (GI) comprising over 10 times as many cells as the human body. These bacteria are both of commensal and pathogenic strains in which commensal bacteria and antimicrobial peptides have an important role of controlling the intestinal colonization. The intestinal flora is sampled by the membranous cells (M cells) that are present in the follicle associated epithelium (FAE). Antigens encounter immune cells found in Peyer’s patches located in the distal ileum with FAE overlaying them. Due to environmental factors, genetic predisposition, immune dysregulation or dysbiosis the balance can be shifted which, in turn, will lead to the defect in the barrier function, leading to the development of disorders such as Crohn’s disease (CD). CD is a chronic inflammation in the GI tract, often originating in the distal ileum in FAE and associated with an increased number of adherent invasive strains of bacteria. Specifically adherent invasive E.coli (AIEC) that have been isolated from the ileum and colon of CD patients.

    The aim of the present thesis was to study bacterial epithelial interaction during inflammation in in vivo, ex vivo and in vitro models.

    In the first project we found that that Faecalibacterium prausnitzii (FP), possess anti-inflammatory properties in the ileum of an in vivo DSS induced colitis mouse model.

    In the second project, we discovered that infliximab, known to have anti-inflammatory effects by binding soluble TNF and blocking TNF receptors, reduces bacterial transcytosis across colonic biopsies of CD patients and decreases transcytosis and internalization in cell monolayers in vitro. Moreover, we demonstrated that HM427 bacteria, isolated from colonic mucosa of CD patients, uses lipid raft formations to penetrate the barrier under the influence of TNF in an in vitro model.

    In project three, we demonstrated that LF82 bacteria, which is an adherent invasive strain of E.coli that has been isolated from the ileum of CD patients, exploits FAE of CD patients and non-IBD control patients to penetrate the barrier via the CEACAM6 receptor and long polar fimbriae. We further demonstrated that there is an increased expression of CEACM6 receptor in the FAE of CD patients, which leads to increased transcytosis of LF82 compared to non-IBD control group.

    In project four, our results suggested that human α-defensin 5 significantly decreases the passage of LF82 bacteria in an in vitro and ex vivo models. Moreover, we demonstrated that CD patients have a lower expression of human α-defensin 5 in the crypts compared to the non-IBD control patients.

    Taken together, our findings have given a novel insight into the etiology of CD and into the mechanisms involved in bacterial-epithelial interaction in CD.

    List of papers
    1. Faecalibacterium prausnitzii supernatant improves intestinal barrier function in mice DSS colitis
    Open this publication in new window or tab >>Faecalibacterium prausnitzii supernatant improves intestinal barrier function in mice DSS colitis
    Show others...
    2013 (English)In: Scandinavian Journal of Gastroenterology, ISSN 0036-5521, E-ISSN 1502-7708, Vol. 48, no 10, p. 1136-1144Article in journal (Refereed) Published
    Abstract [en]

    Objective. The intestinal microbiota plays a substantial role in the pathogenesis of inflammatory bowel disease (IBD). Faecalibacterium prausnitzii (FP) is underrepresented in IBD patients and have been suggested to have anti-inflammatory effects in mice. Increased intestinal permeability is common in IBD but the relationship between FP and intestinal barrier function has not been investigated. Our aim was to study treatment with FP supernatant on intestinal barrier function in a dextran sodium sulfate (DSS) colitis mice model. Material and methods. C57BL/6 mice received 3% DSS in tap water ad libitum during five days to induce colitis. From day 3 the mice received a daily gavage with FP supernatant or broth during seven days. Ileum and colon were mounted in Ussing chambers for permeability studies with Cr-51-EDTA and Escherichia coli K-12. Colon was saved for Western blot analyses of tight junction proteins. Results. DSS-treated mice showed significant weight loss and colon shortening. Gavage with FP supernatant resulted in a quicker recovery after DSS treatment and less extensive colonic shortening. Ileal mucosa of DSS mice showed a significant increase in Cr-51-EDTA-passage compared to controls. Cr-51-EDTA passage was significantly decreased in mice receiving FP supernatant. No significant differences were observed in passage of E. coli K12. Western blots showed a trend to increased claudin-1 and claudin-2 expressions in DSS mice. Conclusions. Supernatant of FP enhances the intestinal barrier function by affecting paracellular permeability, and may thereby attenuate the severity of DSS-induced colitis in mice. These findings suggest a potential role of FP in the treatment of IBD.

    Place, publisher, year, edition, pages
    Informa Healthcare, 2013
    Keywords
    dextran sodium sulfate, inflammatory bowel disease, permeability, probiotics, tight junctions
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-99406 (URN)10.3109/00365521.2013.828773 (DOI)000324761000005 ()
    Note

    Funding Agencies|Swedish Research Council|VR-M: K2012-55X-12618-16-3|

    Available from: 2013-10-17 Created: 2013-10-17 Last updated: 2018-04-27
    2. Infliximab restores colonic barrier to adherent-invasive E. coli in Crohn's disease via effects on epithelial lipid rafts
    Open this publication in new window or tab >>Infliximab restores colonic barrier to adherent-invasive E. coli in Crohn's disease via effects on epithelial lipid rafts
    Show others...
    2018 (English)In: Scandinavian Journal of Gastroenterology, ISSN 0036-5521, E-ISSN 1502-7708, Vol. 53, no 6, p. 677-684Article in journal (Refereed) Published
    Abstract [en]

    Objective: Infliximab is important in the therapeutic arsenal of Crohn’s disease (CD). However, its effect on mucosal barrier function is not fully understood. Adherent-invasive Escherichia coli (AIEC) are important in CD pathophysiology, but the transmucosal uptake routes are partly unknown. We investigated effects of infliximab on uptake of colon-specific AIEC HM427 across CD colonic mucosa.

    Materials and methods: Endoscopic biopsies from non-inflamed colon of seven patients with CD, before and after two infliximab infusions, and eight non-inflammation controls, were mounted in Ussing chambers. Paracellular permeability (51Cr-EDTA) and transmucosal passage of GFP-expressing HM427 were studied. Mechanisms of HM427 transepithelial transport were investigated in Caco-2 monolayers treated with TNF, in the presence of infliximab and/or endocytosis inhibitors.

    Results: Before infliximab treatment, colonic passage of HM427 [CD: 2475 CFU (450–3000); controls 1163(225–1950)] and 51Cr-EDTA permeability were increased in CD (p < .05), but were restored to control levels by infliximab (CD: 150 (18.8–1069)). In TNF-exposed Caco-2 monolayers HM427 transport and lipid rafts/HM427 co-localization was decreased by infliximab. The lipid raft inhibitor methyl-β-cyclodextrin decreased HM427 transport.

    Conclusion: Infliximab restored the colonic barrier to AIEC in CD; an effect partially mediated by blocking lipid rafts in epithelial cells. This ability likely contributes to infliximab’s clinical efficacy in colonic CD.

    Place, publisher, year, edition, pages
    Taylor & Francis, 2018
    Keywords
    Inflammatory bowel disease, microbiology, large intestine, intestinal barrier function, adherent invasive E. coli
    National Category
    Gastroenterology and Hepatology
    Identifiers
    urn:nbn:se:liu:diva-147615 (URN)10.1080/00365521.2018.1458146 (DOI)000438146900008 ()29688802 (PubMedID)
    Note

    Funding agencies: Swedish Research Council-Medicine [VR-MH 2014-02537]; ALF Grants Region Ostergotland

    Available from: 2018-04-27 Created: 2018-04-27 Last updated: 2019-04-30Bibliographically approved
  • 99290.
    Yakymenko, Irina I.
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Berggren, Karl-Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Correlation and random donors effects on electron transport in wide semiconductor quantum point contacts2015Conference paper (Other academic)
    Abstract [en]

    We study effects of randomly distributed impurities on spin polarization and electronlocalization in realistic semiconductor quantum point contacts (QPCs). To this end we usedensity functional theory in local spin-density approximation (LSDA). Previous studies (as,for example, in [1]) have been restricted to the Thomas-Fermi approximation, and thus theeffects of electron correlation and realistic confinement potentials were beyond the subject.Our studies have been performed for the two geometries of the gates, the first one with onlysplit gates, and the other one with an additional top gate situated over the split gates. In thelatter case there is a possibility to vary electron density within a fixed confinement whichgives an opportunity to separate the effects on conductance caused by impurities and electronelectroninteractions in a more distinct way. In both cases we recover the conventionalfluctuation free parabolic electrostatic potential when the distance between the donor layerand the two-dimensional electron gas (2DEG) exceeds ~50 nm. In the opposite case, i.e.,when the randomly distributed donors are placed more close to the 2DEG layer, there aredrastic changes like the localization of electrons in the vicinity of the confinement potentialminima which gives rise to fluctuation in conductance and resonances. At the same time theusual conductance steps vanish. By charging asymmetrically the split gates voltage wecalculate the conductance as a function of the voltage applied to the top gate. In this way wefind that resonances in conductance caused by randomly distributed donors are shifted anddescreased in amplitude while the anomalies caused by interaction effects remain unmodified.Resonance peaks in the conductance derive from localized states within the QPC due torandom fluctuations. The nature of electron localization has been discussed in our previousstudy [2] where we stress the crucial role of the shape of confinement potential on theformation of electron localization. In the present study we have shown that electronlocalization may be caused by randomly distributed donors and play an important role inelectron transport, especially near the pinch-off regime. The results of our numericalsimulations agree qualitatively with experimental studies [3-4]. We have also shown that fora wide QPC spin polarization appears in the form of stripes. This finding may be interesting inview of experimental study in [5] where it has been shown that the structure of such kind canbe responsible for the anomalous behavior of the quantized conductance of a quantum wire inthe shallow confinement limit. We also discuss the diminished effect of partially ionizedrandom donors on the electronic potentials and the appearance of short-range order among thedonors. The results of the present study is important for applications. For example,homogeneity and order of an assembly of nanostructures are crucial for their use in largescaleelectronic and optical systems.[1] J.A. Nixon, J.H. Davies, and H.U. Baranger, Phys. Rev. B 43, 12638 (1991)[2] I. I. Yakimenko, V. S. Tsykunov and K.-F. Berggren, J. Phys. Condens. Matter 25, 072201 (2013)[3] L.W. Smith, K. J. Thomas, M. Pepper, D. A. Ritchie, I. Farrer, J.P. Griffiths, G.A.C. Jones, J. ofPhys.: Conf. Series 376, 012018, (2012)[4] L. W. Smith, H. Al-Taie, F. Sfigakis, P. See, A. A. J. Lesage, B. Xu, J. P. Griffiths, H. E. Beere, G.A. C. Jones, D. A. Ritchie, M. J. Kelly, and C. G. Smith, Phys. Rev. B 90, 045426 (2014).

  • 99291.
    Yakymenko, Iryna
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics .
    Berggren, Karl-Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics .
    Are there bound states in 2D semiconductor constrictions?2007In: Sweden-Japan QNANO Workshop, December 13-14 2007,2007, 2007Conference paper (Other academic)
    Abstract [en]

        

  • 99292.
    Yakymenko, Iryna
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Berggren, Karl-Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Spin magnetization and electron localization in semiconductor quantum wires and quantum point contacts2012Conference paper (Other academic)
    Abstract [en]

    The physics of low-dimensional semiconductor structures such as quantum wires (QW) and quantum point contacts (QPCs) has developed into an important part of nanotechnology, especially in connection with spintronics and quantum information. In our current studies we focus on electronic states, effects of electron interactions and conductance anomalies in semiconductor quantum point contacts and wires with different geometries to a model GaAs/AlGaAs device [1]. Using the local spin density approximation (LSDA) we recover spin-polarized states in the middle of a conventional QPC results in the 0.7 (2e2/h) conductance anomaly as well as spin-split states near the two edges of the QPC that may be associated with the conductance anomaly in the vicinity of 0.25 (2e2/h). Effects of spontaneous magnetization might be also used for spintronics applications such as spin filters and all-electric QPC spin-polarizer. These systems are physically rich and constantly bring new experimental data such as the unusual conductance behavior in the case of shallow confinement potential in a low electron density regime, the anomalous properties of the 2DEG around the pinch-off regime and the formation of bound states with Kondo physics involved. This leads to the study of ballistic transport in low-dimensional semiconductor-based nanostructures in the ultralow electron density domain where the interaction-induced localization of electrons takes place. By means of LSDA we have shown that the localization of electrons within the barrier embedded in the wire and that the localization is highly dependent on the sharpness and length of the potential barrier. For a shallow barrier-free wire we retraced the structural transitions at low densities from a single chain of localized states to double and triple chains (Wigner spin lattices). We have found that the double chain appears as a double zig-zag co nfiguration [2] . Localized electrons may have interesting applications for semiconductor nanodevices. Indeed the formation of bound state and spin binding within QPC confinement potential opens possibilities to store information and to realize qubits in quantum circuits. We have studied the electron transport in a quantum wire in the presence of bias between source and drain [3]. Our work has confirmed that spontaneous spin splitting does occur within the wire and it is responsible for both the 0.25 and 0.85 plateaus. We have also shown that the 0.25 plateau consists of two regions, one that is spin polarized, and another that is degenerate with a conductance that remains essentially the same at both sides of the transition. This result is of potential interest for semiconductor spintronics since it opens a new possibility for spin manipulation by electric field. [1] K.-F. Berggren and I.I. Yakimenko. J. Phys.: Condens. Matter 20, 164203 (2008). [2] E. Welander, K.-F. Berggren, I. I. Yakimenko. Phys. Rev. B 82, 073307 (2010). [3] H. Lind, I. I. Yakimenko, K.-F. Berggren. Phys. Rev. B 83, 075308 (2011).

  • 99293.
    Yakymenko, Iryna
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics .
    Berggren, Karl-Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics .
    Tsykunov, V. S.
    University of Kiev.
    Shevchenko, V.P.
    University of Kiev.
    On the use of parallel computing in studies of physical properties of nanostructures2009In: Bulletin of University of Kiev: Physics and Mathematics, Vol. N4, p. 195-200Article in journal (Refereed)
  • 99294.
    Yakymenko, Iryna I.
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Berggren, Karl-Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Bound states and electron localization in low-dimensional semiconductor quantum point contacts2012Conference paper (Other academic)
  • 99295.
    Yakymenko, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics.
    Modelling of injection of electrons by low-dimensional nanowire into a reservoir2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    High-mobility two-dimensional electron gas (2DEG) which resides at the interface between GaAs and AlGaAs layered semiconductors has been used experimentally and theoretically to study ballistic electron transport. The present project is motivated by recent experiments in magnetic electron focusing. The proposed device consists of two quantum point contacts (QPCs) serving as electron injector and detector which are placed in the same semiconductor GaAs/AlGaAs heterostructure. This thesis is focused on the theoretical study of electron flow coming from the injector QPC (a short quantum wire) and going into an open two-dimensional (2D) reservoir. The transport is considered for non-interacting electrons at different transmission regimes using the mode-matching technique. The proposed mode-matching technique has been implemented numerically using Matlab software. Electron flow through the quantum wire with rectangular, conical and rounded openings has been studied with and without an applied electric bias. We have found that the geometry of the opening does not play a crucial role for the electron flow propagation while the conical opening allows the electrons to travel longer distances into the 2D reservoir. When electric bias is applied, the electron flow also penetrates farther into the 2D region. The results of this study can be applied in designing magnetic focusing devices.

  • 99296.
    Yakymenko, Ivan
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Yakymenko, Irina I.
    Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics.
    Berggren, Karl-Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Basic modelling of effects of geometry and magnetic field for quantum wires injecting electrons into a two-dimensional electron reservoir2019In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 31, no 34, article id 345302Article in journal (Refereed)
    Abstract [en]

    High-mobility two-dimensional electron gas (2DEG) which resides at the interface between GaAs and AlGaAs layered semiconductors has been used experimentally and theoretically to study ballistic electron transport. The present paper is motivated by recent experiments in magnetic electron focusing. The proposed device consists of two quantum point contacts (QPCs) serving as electron injector and collector which are placed in the same semiconductor GaAs/AlGaAs heterostructure. Here we focus on a theoretical study of the injection of electrons via a quantum wire/QPC into an open two-dimensional (2D) reservoir. The transport is considered for non-interacting electrons at different transmission regimes using the mode-matching technique. The proposed mode-matching technique has been implemented numerically. Electron flow through the quantum wire with hard-wall rectangular, conical and rounded openings has been studied. We have found for these three cases that the geometry of the opening does not play a crucial role for the electron propagation. When a perpendicular magnetic field is applied the electron paths in the 2D reservoir are curved. We analyse this case both classically and quantum-mechanically. The effect of spin-splitting due to exchange interactions on the electron flow is also considered. The effect is clearly present for realistic choices of device parameters and consistent with observations. The results of this study may be applied in designing magnetic focusing devices and spin separation.

    The full text will be freely available from 2020-06-04 08:00
  • 99297.
    Yakymenko, Olena
    et al.
    Linköping University, Department of Clinical and Experimental Medicine, Division of Surgery, Orthopedics and Oncology. Linköping University, Faculty of Medicine and Health Sciences.
    Schoultz, Ida
    Department of Medical Sciences, Faculty of Health and Medicine, Örebro University, Örebro, Sweden.
    Gullberg, Elisabet
    Region Östergötland, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Surgery in Linköping. Linköping University, Faculty of Medicine and Health Sciences. Linköping University, Department of Clinical and Experimental Medicine.
    Ström, Magnus
    Linköping University, Department of Clinical and Experimental Medicine, Division of Neuro and Inflammation Science. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Heart and Medicine Center, Department of Gastroentorology.
    Almer, Sven
    Department of Medicine, Karolinska Institutet, Stockholm, Sweden / GastroCentrum, Karolinska University Hospital, Stockholm, Sweden.
    Wallon, Conny
    Linköping University, Department of Clinical and Experimental Medicine, Division of Surgery, Orthopedics and Oncology. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Surgery in Linköping.
    Wang, Arthur
    Gastrointestinal Research Group, Cumming School of Medicine, University of Calgary, Calgary, Canada..
    Keita, Åsa
    Linköping University, Department of Clinical and Experimental Medicine, Division of Surgery, Orthopedics and Oncology. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Surgery in Linköping.
    Campbell, Barry J.
    Gastroenterology Research Unit, Department of Cellular and Molecular Physiology, University of Liverpool, Liverpool, UK.
    McKay, Derek M.
    Gastrointestinal Research Group, Cumming School of Medicine, University of Calgary, Calgary, Canada.
    Söderholm, Johan D
    Linköping University, Department of Clinical and Experimental Medicine, Division of Surgery, Orthopedics and Oncology. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Surgery in Linköping.
    Infliximab restores colonic barrier to adherent-invasive E. coli in Crohn's disease via effects on epithelial lipid rafts2018In: Scandinavian Journal of Gastroenterology, ISSN 0036-5521, E-ISSN 1502-7708, Vol. 53, no 6, p. 677-684Article in journal (Refereed)
    Abstract [en]

    Objective: Infliximab is important in the therapeutic arsenal of Crohn’s disease (CD). However, its effect on mucosal barrier function is not fully understood. Adherent-invasive Escherichia coli (AIEC) are important in CD pathophysiology, but the transmucosal uptake routes are partly unknown. We investigated effects of infliximab on uptake of colon-specific AIEC HM427 across CD colonic mucosa.

    Materials and methods: Endoscopic biopsies from non-inflamed colon of seven patients with CD, before and after two infliximab infusions, and eight non-inflammation controls, were mounted in Ussing chambers. Paracellular permeability (51Cr-EDTA) and transmucosal passage of GFP-expressing HM427 were studied. Mechanisms of HM427 transepithelial transport were investigated in Caco-2 monolayers treated with TNF, in the presence of infliximab and/or endocytosis inhibitors.

    Results: Before infliximab treatment, colonic passage of HM427 [CD: 2475 CFU (450–3000); controls 1163(225–1950)] and 51Cr-EDTA permeability were increased in CD (p < .05), but were restored to control levels by infliximab (CD: 150 (18.8–1069)). In TNF-exposed Caco-2 monolayers HM427 transport and lipid rafts/HM427 co-localization was decreased by infliximab. The lipid raft inhibitor methyl-β-cyclodextrin decreased HM427 transport.

    Conclusion: Infliximab restored the colonic barrier to AIEC in CD; an effect partially mediated by blocking lipid rafts in epithelial cells. This ability likely contributes to infliximab’s clinical efficacy in colonic CD.

  • 99298.
    Yalamanchili, K.
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
    Wang, Fei
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering. Saarland University, Germany.
    Schramm, Isabella
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering. Saarland University, Germany.
    Andersson, J. M.
    Seco Tools AB, Sweden.
    Johansson Jöesaar, Mats P.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering. Seco Tools AB, Sweden.
    Tasnadi, Ferenc
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Muecklich, F.
    Saarland University, Germany.
    Ghafoor, Naureen
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Odén, Magnus
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering.
    Exploring the high entropy alloy concept in (AlTiVNbCr)N2017In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 636, p. 346-352Article in journal (Refereed)
    Abstract [en]

    We have explored the high entropy alloy (HEA) concept in the AlTiVNbCr-nitride material system. (AlTiVNbCr)N coatings synthesized by reactive cathodic arc deposition are close to an ideal cubic solid solution with a positive mean-field enthalpy of mixing of 0.06 eV/atom. First principle calculations showa higher thermodynamic stability for the solid solution relative to their binaries thereby indicating a possible entropy stabilization at a temperature above 727 degrees C. However, the elevated temperature annealing experiments show that the solid solution decomposes to w-AlN and c-(TiVNbCr)N. The limited thermal stability of the solid solution is investigated in relation to several thermodynamic parameters. We suggest that the HEA designed multiprincipal element (AlTiVNbCr) N solid solutions are in a metastable state. (C) 2017 Published by Elsevier B.V.

  • 99299.
    Yalamanchili, Kumar
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology.
    Forsén, Rikard
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology.
    Jiménez-Piqué, Emilio
    Departament de Ciència del Materials i Enginyeria Metal·lúrgica, Universitat Politècnica de Catalunya, Barcelona, Spain.
    Johansson Jöesaar, Mats P.
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology.
    Roa, J.J.
    Department of Materials Science and Metallurgical Engineering, University of Barcelona, Barcelona, Spain.
    Ghafoor, Naureen
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology.
    Odén, Magnus
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology.
    Structure, deformation and fracture of arc evaporated Zr-Si-N ternary hard films2014In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 258, p. 1100-1107Article in journal (Refereed)
    Abstract [en]

    Zr-Si-N films with varying Si contents were grown on WC-Co substrates with an industrial scale reactive cathodic arc deposition technique. The microstructural changes correlate to variation in mechanical properties with different deformation mechanisms dominating for different structures. Si forms a substitutional solid solution in the cubic ZrN lattice up to 1.8 at. % in a fine columnar structure. Further Si additions results in precipitation of an amorphous (a)-SiNX phase and evolution of a nanocomposite structure (nc ZrN-a SiNX) which has completely suppressed the columnar structure at 6.3 at. % Si. The rotation-induced artificial layering during film growth was used as a marker to visualize the deformation of the film. A dislocation-based homogeneous plastic deformation mechanism dominates the columnar structure, while grain boundary sliding is the active mechanism mediating heterogeneous plastic deformation in the nanocomposite structure. Film hardness increases with increasing Si content in the columnar structure due to an effective solid solution strengthening. The deformation mechanism of localized grain boundary sliding in the nanocomposite structure results in lower hardness. When cracking is induced by indentation, the fine columnar structure exhibits pronounced crack deflection that results in higher fracture resistance compared to the nanocomposite films.

  • 99300.
    Yalamanchili, Kumar
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology.
    Roa, J.J.
    Department of Materials Science and Metallurgical Engineering, University of Barcelona, Barcelona, Spain.
    Jiménez-Piqué, Emilio
    Departament de Ciència del Materials i Enginyeria Metal·lúrgica, Universitat Politècnica de Catalunya, Barcelona, Spain.
    Johansson Jöesaar, Matts P.
    Ghafoor, Naureen
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology.
    Odén, Magnus
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology.
    Influence of microstructure and mechanical properties on the wear behavior of reactive arc deposited Zr-Si-N coatingsManuscript (preprint) (Other academic)
    Abstract [en]

    Zr-Si-N coatings were grown over WC-Co substrates by an industrial reactive arc deposition technique. Si content of the coatings was varied between 0.2 and 6.3 at. % to cause a microstructural transition from a columnar to an equiaxed nanocomposite microstructure resulting in alterations of the mechanical properties such as hardness, elastic modulus, and fracture resistance. A reciprocating sliding wear test with a counter material of WC-Co shows a systematic change in wear rate as a function of Si content of the coatings. A maximum wear rate of 1.4x10-5 mm3/Nm is seen for the coating with 1.8 at. % Si (columnar microstructure), which then gradually decreases to 0.6x10-5 mm3/Nm at 6.3 at. % Si (nanocomposite structure). Electron microscopy observations of the wear track reveal tribooxidation as the dominating wear mode. The growth rate of the tribo-oxide layer is the wear rate determining mechanism. Higher growth rate of tribo-oxide layer in the columnar structured coating leads to layer delamination and high wear rate. While the lower growth rate of tribo-oxide layer in the nanocomposite coating results in reduced wear rate of the coatings. Nanocomposite coatings show superior resistance to both static and tribo-oxidation compared to the columnar structured coatings.

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