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  • 11451.
    Zhu, Jun
    et al.
    Uppsala University, Uppsala, Sweden.
    Dahlstrand, Christian
    Uppsala University, Uppsala, Sweden.
    Smith, Joshua R.
    Uppsala University, Uppsala, Sweden; Humboldt State University, Arcata, USA.
    Villaume, Sebastien
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics. Linköping University, The Institute of Technology. Uppsala University, Uppsala, Sweden.
    Ottosson, Henrik
    Uppsala University, Uppsala, Sweden.
    On the Importance of Clar Structures of Polybenzenoid Hydrocarbons as Revealed by the pi-Contribution to the Electron Localization Function2010In: Symmetry, ISSN 2073-8994, E-ISSN 2073-8994, Vol. 2, no 3, p. 1653-1682Article in journal (Refereed)
    Abstract [en]

    The degree of pi-electron (de) localization and aromaticity of a series of polybenzenoid hydrocarbons (PBHs) has been analyzed through the pi-contribution to the electron localization function (ELF pi), calculated at the B3LYP/ 6-311G(d, p) hybrid density functional theory level. The extent of. -electron delocalization in the various hexagons of a PBH was determined through analysis of the bifurcation values of the ELF. basins (BV(ELF.)), the spans in the bifurcation values in each hexagon (BV(ELF pi)), and the ring-closure bifurcation values of the ELF pi (RCBV(ELF pi)). These computed results were compared to the qualitative description of local aromaticities of the different hexagons in terms of Clar structures with pi-sextets. Benzene, [18] annulene, and thirty two PBHs were analyzed at their equilibrium geometries, and benzene and triphenylene were also analyzed at bond length distorted structures. In general, the description of PBHs in terms of Clar valence structures is supported by the ELF pi properties, although there are exceptions. For PBHs at their equilibrium geometries there is a clear sigmoidal relationship between the CC bond lengths and the amount of pi-electron (de) localization at these bonds, however, this relationship is lost for bond distorted geometries. In the latter cases, we specifically examined benzene in D3h symmetric " 1,3,5-cyclohexatriene" structures and triphenylene in eight different structures. From the distorted benzenes and triphenylenes it becomes clear that there is a distinct tendency for the pi-electron network to retain delocalization (aromaticity). The ELF. analysis thus reveals an antidistortive rather than a distortive behavior of the pi-electrons in these investigated compounds.

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  • 11452. Zhu, Q.
    et al.
    Karlsson, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Byszewski, M.
    Rudra, A.
    Pelucchi, E.
    He, Z.
    Kapon, E.
    Hybridization of electron and hole states in pyramidal quantum dot molecules2008In: The 5th International Conerence on Semiconductor Quantum Dots QD2008,2008, 2008Conference paper (Other academic)
  • 11453. Zhu, Q.
    et al.
    Karlsson, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Rudra, A.
    Pelucchi, E.
    Byszewski, M.
    Gallo, P.
    Kapon, E.
    Control of Light Polarization using Semiconductor Quantum Dot Molecules2007In: OSA topical Conference in Nanophotonics,2007, 2007Conference paper (Other academic)
  • 11454. Zhu, Q.
    et al.
    Karlsson, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Rudra, A.
    Pelucchi, E.
    Byszewski, M.
    Gallo, P.
    Kapon, E.
    Quantum Dot Molecules and Superlattices Realized with Modulated Quantum Wire Heterostructures2007In: 13th International Conference Modulated Semiconductor Structures MSS 13,2007, 2007Conference paper (Other academic)
  • 11455. Zhu, Q.
    et al.
    Pelucchi, E.
    Karlsson, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Dalessi, S.
    Dupertuis, M.-A.
    Kapon, E.
    Experimental Observation of Transition from 2D to 3D Quantum Confinement in Semiconductor Quantum Wires/Quantum dots2006In: SCOPES Seminar,2006, 2006Conference paper (Other academic)
  • 11456. Zhu, Q.
    et al.
    Pelucchi, E.
    Karlsson, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Dalessi, S.
    Dupertuis, M.-A.
    Moret, N.
    Oberli, D.Y.
    Kapon, E.
    Semiconductor Quantum Wires with Controlled Length and Confinement Potential2006In: 28th International Conference on the Physics of Semiconductors ICPS,2006, 2006Conference paper (Other academic)
  • 11457. Zhu, Q.
    et al.
    Pelucchi, E.
    Karlsson, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Moret, N.
    Oberli, D.
    Kapon, E.
    Continuous transition from 2D to 3D quantum confinement realized with pyramidal quantum wires and dots2006In: 4th International Conference on Quantum Dots,2006, 2006Conference paper (Other academic)
  • 11458.
    Zhu, Qing
    et al.
    Ecole Polytech, Lausanne.
    Karlsson, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Byszewski, Marcin
    Ecole Polytech, Lausanne.
    Rudra, Alok
    Ecole Polytech, Lausanne.
    Pelucchi, Emanuele
    Ecole Polytech, Lausanne.
    He, Zhanbing
    Ecole Polytech, Lausanne.
    Kapon, Eli
    Ecole Polytech, Lausanne.
    Hybridization of Electron and Hole States in Semiconductor Quantum-Dot Molecules2009In: Small, ISSN 1613-6810, E-ISSN 1613-6829, Vol. 5, no 3, p. 329-335Article in journal (Refereed)
    Abstract [en]

    A novel QD-molecule system is realized using metal–organic vapor-phase epitaxy growth. The dots are tunnel coupled via connected quantum wires (QWRs). The stronger tunnel coupling in this integrated QD-QWR system allows the hybridization of both electron and hole states, yielding direct-real-space excitonic molecules (see image). The structure holds promise for nanophotonic devices for quantum-information-processing applications.

  • 11459.
    Zhu, Xiaolong
    et al.
    Technical University of Denmark, Lyngby.
    Ou, Yiyu
    Technical University of Denmark, Lyngby.
    Jokubavicius, Valdas
    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.
    Hansen, Ole
    Technical University of Denmark, Lyngby.
    Ou, Haiyan
    Technical University of Denmark, Lyngby.
    Mortensen, N. Asger
    Technical University of Denmark, Lyngby.
    Xiao, Sanshui
    Technical University of Denmark, Lyngby.
    Broadband light-extraction enhanced by arrays of whispering gallery resonators2012In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 101, no 24Article in journal (Refereed)
    Abstract [en]

    We demonstrate a light-extraction approach using a whispering gallery resonators array. The wavelength-scale resonant dielectric nanospheres support whispering gallery modes, which can be coupled with the confined waveguide modes inside the bulk material, thus dramatically improving light extraction. Broadband light-extraction enhancement across the entire visible spectral range is achieved by exciting three low-order and low-quality-factor resonances. As an example, the broadband extraction enhancement of about 50% is obtained for the emission of fluorescent SiC at all the tested angles. The experimental results are supported by numerical simulations. Our light-extraction strategy could enable the manufacturing of high-throughput, nondestructive, and affordable optical coating in a variety of optical devices.

  • 11460.
    Zhuang, Wenliu
    et al.
    Chalmers, Sweden .
    Zhen, Hongyu
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Kroon, Renee
    Chalmers, Sweden .
    Tang, Zheng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Hellstrom, Stefan
    Chalmers, Sweden .
    Hou, Lintao
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Wang, Ergang
    Chalmers, Sweden .
    Gedefaw, Desta
    Chalmers, Sweden .
    Inganäs, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Zhang, Fengling
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Andersson, Mats R.
    Chalmers, Sweden .
    Molecular orbital energy level modulation through incorporation of selenium and fluorine into conjugated polymers for organic photovoltaic cells2013In: JOURNAL OF MATERIALS CHEMISTRY A, ISSN 2050-7488, Vol. 1, no 43, p. 13422-13425Article in journal (Refereed)
    Abstract [en]

    We demonstrated an effective chemical approach to modulate the energy levels of conjugated polymers by synergistically combining fluorine substitution and thiophene-selenophene exchange. Such modifications from TQ1 resulted in a significantly enhanced open-circuit voltage up to 1.0 V while retaining high photovoltaic performance.

  • 11461.
    Zhuravlev, K S
    et al.
    Physics Dept, Novosibirsk.
    Alexandrov, I A
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Linear polarized photoluminescence from GaN quantum dots imbedded in AlN matrix2010Conference paper (Refereed)
    Abstract [en]

    We report microphotoluminescence studies of GaN/AlN quantum dots grown along the (0001) crystal axis by molecular-beam epitaxy on sapphire substrates. To obtain quantum dots with different density and size a nominal GaN coverage was varied from 1 to 4 monolayers. The highest density of quantum dots was about 1011 cm-2, so about 103 quantum dots was excited in experiments. We found that the photoluminescence intensity of a sample with the smallest amount of deposited GaN decreases in more than two orders of magnitude under continuous-wave laser exposure during about 30 minutes and then it remains stable. The photoluminescence intensity of the rest samples was time-independent quantity. The emission band of the former sample exhibits a prominent linear polarization along the growth plane. We assume that the quite high degree of polarization can be due anisotropy of strain and/or shape of the quantum dots formed near dislocations which act also as recombination centers causing photoluminescence quenching.

  • 11462.
    Zhuravlev, K S
    et al.
    n/a.
    Alexandrov, I A
    n/a.
    Holtz, Per-Olof
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Linearly polarized photoluminescence from GaN quantum dots embedded in AlN matrix2009In: International Conference on Physics, Chemistry and Applications of Nanostructures, Belarus, 2009Conference paper (Refereed)
  • 11463. Zhuravlev, K S
    et al.
    Mansurov, V G
    Yu, A
    Nikitin, A
    Larsson, Mats
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Holtz, Per-Olof
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Mobile and immobile photoluminescence bands from single hexagonal GaN quantum dots embedded in an AlN matrix2008In: ICPS 29th International Conference on the Physics of Semiconductors,2008, 2008Conference paper (Refereed)
  • 11464. Zhuravlev, KS
    et al.
    Mansurov, VG
    YU, A
    Nikitin, A
    Larsson, Mats
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Holtz, Per-Olof
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Power dependence of photoluminescence from single hexagonal GaN quantum dots formed in an AlN matrix2007In: NANO-2007 workshop,2007, 2007Conference paper (Refereed)
  • 11465. Zhuravlev, K.S.
    et al.
    Ree, D.D.
    Mansurov, V.G.
    Nikitin, A.Yu.
    Paskov, Plamen
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Holtz, Per-Olof
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Microphotoluminescence of GaN/AlN quantum dots grown by MBE2006In: Physica Status Solidi. C, Current topics in solid state physics, ISSN 1610-1634, E-ISSN 1610-1642, Vol. 3, p. 2048-2051Article in journal (Refereed)
    Abstract [en]

    Presented at: The 6th International Conference on Nitride Semiconductors (ICNS6), Bremen, Germany, Aug 28-Sept 2, 2005

  • 11466. Zhuravlev, KS
    et al.
    Shamirzaev, TS
    Larsson, Mats
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Holtz, Per-Olof
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Photo-luminescence of single InAs quantum dots in an AlAs matrix2007In: NANO-2007 workshop,2007, 2007Conference paper (Refereed)
  • 11467.
    Zhybak, Mikael
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, The Institute of Technology.
    Beni, Valerio
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, The Institute of Technology.
    Dempsey, Eithne
    Centre for Research in Electroanalytical Technologies, Department of Science, Dublin, Ireland.
    Vagin, Mikhail Y
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, The Institute of Technology.
    Turner, Anthony
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, The Institute of Technology.
    Korpan, Yaroslav
    Laboratory of Biomolecular Electronics, Institute of Molecular Biology and Genetics, National Academy of Sciences of Ukraine, Kyiv, Ukraine.
    Copper/Nafion/PANI Nanocomposite as an electrochemical transducer for creatinine and urea enzymatic biosensing2014In: 24th Anniversary World Congress on Biosensors – Biosensors 2014, Elsevier, 2014Conference paper (Other academic)
    Abstract [en]

    Chronic Kidney diseases (CKD) affect, to different degrees, ca. 25 million Americans and 19 million Europeans. Monitoring of creatinine and urea levels is of great importance for a correct evaluation of the status of patients and for their treatment. In this paper, we present the development of creatinine and urea enzymatic biosensors, based on a novel ammonium ion-specific Copper/Nafion/Polyanyline (PANI) nanocomposite electrode (Fig. 1A), and suitable for PoC and decentralised diagnostic applications. . Studies on the nanocomposite electrode revealed its high sensitivity and specificity towards ammonium, in respect to amino acids, creatinine and urea, with response range between 5 and 75 μM (Fig. 1B) and with a detection limit of 1 μM. To demonstrate its suitability as transducer in biosensors, creatinine and urea biosensors were fabricated by immobilising creatinine deiminase or urease, respectively, on the nanocomposite surface. Optimisation of the enzyme immobilisation demonstrated that the incorporation of lactitol markedly improved the stability of the biosensors. The response range of the creatinine biosensor was 2 to 100 μM, which fits well with the normal levels of creatinine in healthy people (30-150 µM).

    The urea biosensor had a response range of 5 to 100 µM. A limit of quantification of 1 µM was achieved for both the biosensors.

    Evaluation of the performance of the biosensors in real sample matrices and cross reactivity studies are currently on-going. We envisage that the proposed design will be particularly compatible with fully-printed systems thus offering a viable route to the mass production of inexpensive sensors for mobile health.

     

     

  • 11468.
    Zhybak, Mikael T
    et al.
    Institute of Molecular Biology and Genetics, NAS of Ukraine, Ukraine.
    Fayura, L.Y.
    Institute of Cell Biology, NAS of Ukraine, Ukraine.
    Boretsky, Yu R
    Institute of Cell Biology, NAS of Ukraine, Ukraine.
    Dempsey, Eithne
    Centre for Research in Electroanalytical Technologies, Ireland.
    Gonchar, M.V.
    Institute of Cell Biology, NAS of Ukraine, Ukraine.
    Sibirny, A.A.
    Institute of Cell Biology, NAS of Ukraine, Ukraine.
    Turner, Anthony
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, Faculty of Science & Engineering.
    Korpan, Yaroslav
    Institute of Molecular Biology and Genetics, NAS of Ukraine, Ukraine.
    Novel L-arginine amperometric assay based on recombinant arginine deiminase and Nafion/PANi composite2016In: Biosensors 2016 – The World Congress on Biosensors, Elsevier, 2016Conference paper (Other academic)
  • 11469.
    Zhybak, M.T.
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, Faculty of Science & Engineering. Laboratory of Biomolecular Electronics, Institute of Molecular Biology and Genetics, National Academy of Sciences of Ukraine, Kyiv, Ukraine.
    Beni, Valerio
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, Faculty of Science & Engineering.
    Vagin, Mikhail
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, Faculty of Science & Engineering.
    Dempsey, Eithne
    Centre for Research in Electroanalytical Technologies, Department of Science, ITT Dublin, Tallaght, Dublin, Ireland.
    Turner, Anthony
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, Faculty of Science & Engineering.
    Korpan, Y
    Laboratory of Biomolecular Electronics, Institute of Molecular Biology and Genetics, National Academy of Sciences of Ukraine,Kyiv, Ukraine.
    Creatinine and urea biosensors based on a novel ammonium ion-selective copper-polyaniline nano-composite2016In: Biosensors & bioelectronics, ISSN 0956-5663, E-ISSN 1873-4235, Vol. 77, p. 505-511Article in journal (Refereed)
    Abstract [en]

    The use of a novel ammonium ion-specific copper-polyaniline nano-composite as transducer for hydrolase-based biosensors is proposed. In this work, a combination of creatinine deaminase and urease has been chosen as a model system to demonstrate the construction of urea and creatinine biosensors to illustrate the principle. Immobilisation of enzymes was shown to be a crucial step in the development of the biosensors; the use of glycerol and lactitol as stabilisers resulted in a significant improvement, especially in the case of the creatinine, of the operational stability of the biosensors (from few hours to at least 3 days). The developed biosensors exhibited high selectivity towards creatinine and urea. The sensitivity was found to be 85±3.4 mA M−1 cm−2 for the creatinine biosensor and 112±3.36 mA M−1 cm−2 for the urea biosensor, with apparent Michaelis–Menten constants (KM,app), obtained from the creatinine and urea calibration curves, of 0.163 mM for creatinine deaminase and 0.139 mM for urease, respectively. The biosensors responded linearly over the concentration range 1–125 µM, with a limit of detection of 0.5 µM and a response time of 15 s.

    The performance of the biosensors in a real sample matrix, serum, was evaluated and a good correlation with standard spectrophotometric clinical laboratory techniques was found.

  • 11470.
    Zhybak, Mykhailo T.
    et al.
    National Academic Science Ukraine, Ukraine.
    Fayura, Lyubov Y.
    NAS Ukraine, Ukraine.
    Boretsky, Yuriy R.
    Lviv State University of Phys Culture, Ukraine.
    Gonchar, Mykhailo V.
    NAS Ukraine, Ukraine.
    Sibirny, Andriy A.
    NAS Ukraine, Ukraine; Rzeszow University, Poland.
    Dempsey, Eithne
    ITT Dublin, Ireland.
    Turner, Anthony
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, Faculty of Science & Engineering.
    Korpan, Yaroslav I.
    National Academic Science Ukraine, Ukraine.
    Amperometric L-arginine biosensor based on a novel recombinant arginine deiminase2017In: Microchimica Acta, ISSN 0026-3672, E-ISSN 1436-5073, Vol. 184, no 8, p. 2679-2686Article in journal (Refereed)
    Abstract [en]

    The authors describe an amperometric biosensor for the amino acid L-arginine (L-Arg). It is based on the use of a Nafion/Polyaniline (PANi) composite on a platinum screen-printed electrode (Pt-SPE) using a novel recombinant arginine deiminase isolated from Mycoplasma hominis. The protein was over-expressed, purified and employed as a biorecognition element of the sensor. Enzymatic hydrolysis of L-Arg leads to the formation of ammonium ions which diffuse into the Nafion/PANi layer and induce the electroreduction of PANi at a potential of -0.35 V (vs Ag/AgCl). L-Arg sensitivity is 684 +/- 32 A.M-1.m(-2), and the apparent Michaelis-Menten constant K-M(app)) is 0.31 +/- 0.05 mM. The calibration plot is linear over the range 3-200 mu M L-Arg, the limit of detection is 1 mu M, and the response time (for 90% of the total signal change to occur) is 15 s. The sensor is selective and exhibits good storage stability (amp;gt; 1 month without loss in signal). The biosensor was applied to the analysis of L-Arg in pharmaceutical samples and of ammonium and L-Arg in spiked human plasma obtained from blood of healthy volunteers and those with a hepatic disorder. Data generated were found to be in good agreement with a reference fluorometric enzymatic assay.

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  • 11471.
    Zhybak, Mykhailo T.
    et al.
    Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology. Institute of Molecular Biology and Genetics, NAS of Ukraine, Kyiv, 03680, Ukraine .
    Vagin, Mikhail Yu.
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
    Beni, Valerio
    ACREO Swedish ICT, -601 74, Norrköping, SE, Sweden .
    Liu, Xianjie
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Dempsey, Eithne
    Centre for Research in Electroanalytical Technologies, Department of Science, Institute of Technology Tallaght, Tallaght, Dublin, Ireland .
    Turner, Anthony P. F.
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, Faculty of Science & Engineering.
    Korpan, Yaroslav I.
    Institute of Molecular Biology and Genetics, NAS of Ukraine, Kyiv, 03680, Ukraine .
    Direct detection of ammonium ion by means of oxygen electrocatalysis at a copper-polyaniline composite on a screen-printed electrode.2016In: Microchimica Acta, ISSN 0026-3672, E-ISSN 1436-5073, Vol. 183, no 6, p. 1981-1987Article in journal (Refereed)
    Abstract [en]

    A novel electrocatalytic material for oxygen reduction, based on polyaniline in combinationwith copper, was developed and utilised for the direct voltammetric quantification of ammonium ions. Consecutive electrode modification by electrodeposited copper, a Nafion membrane and electropolymerised polyaniline resulted in an electrocatalytic composite material which the retained conductivity at neutral pH. Ammonia complex formation with Cu (I) caused the appearance of oxygen electrocatalysis, which was observed as an increase in cathodic current. This Faradaic phenomenon offered the advantage of direct voltammetric detection and was utilised for ammonium electroanalysis. The developed quantification protocol was applied for ammonium assay in human serum and compared with the routine approach for clinical analysis.

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  • 11472. Ziane, D
    et al.
    Bluet, JM
    Guillot, G
    Godignon, P
    Monserrat, J
    Ciechonski, Rafal
    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.
    Yakimova, Rositsa
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Chen, L
    Mawby, P
    Characterizations of SiC/SiO2 interface quality toward high power MOSFETs realization2004In: Materials Science Forum, Vols. 457-460, 2004, Vol. 457-460, p. 1281-1286Conference paper (Refereed)
    Abstract [en]

    The low channel mobility in N-MOS 4H-SiC transistor is a major key issue for the development of power devices with satisfactory on state characteristics. Previous works have demonstrated that this low channel mobility is due to high interface state density (Dit) near the conduction band edge. Furthermore, the realization of SiC MOSFETs sustaining high reverse field necessitates thick epitaxial layer growth. An important thickness (> 30 gm) unfortunately involves important surface roughness which may result in a high interface trap density (Dit) and surface potential fluctuation (sigma(s)) at the SiC/SiO2 interface. In this study, we focus on SiO2/SiC MOS interface quality characterization as a function of process conditions and material properties (dopant type, thick layer growth technique). Investigations of the oxide quality on thick layers grown by CVD and PVT has been realized using CV under UV lightening and GV techniques. We evidenced that the Dit value (between 10(10) cm(-2).eV(-1) and 9x10(10) cm(-2).eV(-1) from 0.9 Ev to 0.2 eV below Ec) and sigma(s) value (60 mV) were slightly lower for thick PVT layers. A discrepancy in the Dit values obtained from C-V and G-V measurements is attributed to the large surface potential standard deviation. Results from an original oxide growth process using a deposited sacrificial silicon layer under UHV conditions are also presented.

  • 11473. Order onlineBuy this publication >>
    Zidar, Josefina
    Linköping University, Department of Physics, Chemistry and Biology, Biology. Linköping University, Faculty of Science & Engineering.
    The relationship between personality and cognition in the fowl, Gallus gallus2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    To cope with a changing environment, animals have traditionally been considered to behave adaptively to each situation faced. Yet, individual behavioural responses can both differ widely within populations, and show between-individual consistency (i.e. describing variation in animal personality). In this thesis, I focus on individual differences in animal personality and cognition (i.e. how animals perceive, process, store and act on environmental stimuli), and explore the possibility that they are interlinked. I use domestic- and red junglefowl (Gallus gallus ssp.), a species that is cognitively, behaviourally and socially complex, to explore these aspects of behaviour, through a series of studies.

    Animal personality and coping styles are frequently used terms to describe within- and between-individual differences in behaviour, which are consistent over time and across various situations. The terms are often used as synonyms, even though they differ in some respects. In paper I, I show that animal personality and coping styles can be measured in red junglefowl, and that behavioural flexibility might be an important aspect for both. Further, I show that the terms should not be used as synonyms since they describe different aspects of behavioural variation.

    In paper II, I observe large individual variation in both personality traits and learning speed in both chicks and adult red junglefowl. Interestingly, learning performance does not correlate across tasks, contrasting what has been found in humans and rodents. Thus, individuals that learn rapidly in one task are not necessarily fast learners in another task. I observe a relationship between personality and cognition that is task- and age-dependent, in which exploration relates to learning speed, but in opposite directions for chicks compared to adult females. In paper III, I show that red junglefowl chicks that are more behaviourally flexible have a stronger preference for new generalised stimuli, than less behaviourally flexible chicks. Behavioural flexibility was associated with fearfulness, indicating variation in reactive-proactive coping styles. In paper IV, I show that early cognitive stimulation to some extent can affect adult personality, thus showing a causal relationship between personality and cognition. Not all personality traits were affected, which might depend on the type of cognitive stimulation chicks were exposed to.

    Important cognitive processes like perception and decision-making, can contain biases. One such bias is called judgment bias, which describes how individuals interpret ambiguous stimuli on a scale from positive to negative (optimism to pessimism). In paper V, I show that alteration of emotional state can influence such biases. Here, unpredictable stress influence judgment bias negatively, when individuals are housed in simpler, but not in complex environments, suggesting that there is an effect of additive stress that lead to reduced optimism. Complexity instead seems to buffer against negative effects of stress, since individuals in complex environments remained optimistic after stress exposure. Furthermore, increased dopamine activity was associated with optimism in chicks. In paper VI, I find that aspects of personality associate with how chicks judge ambiguity. Highly active individuals are more likely to approach cues than less active individuals, and when approaching, individuals that are slow to approach ambiguous cues are more vigilant when assayed in personality assays. Vigilant individuals might be more worried and reactive, which suggest that emotional traits can influence responses in a judgment bias task.

    Taken together, I show consistent behavioural differences among individuals describing personality and coping styles, and variation in cognition. I show that these traits are related, and that there is an interplay between them, in which cognition can influence personality, and vice versa. I further show that judgment may be affected by the individual’s current affective state and personality. Thus, I show a complex relationship between personality and cognition that in combination with environmental effects can help explain behavioural variation.

    List of papers
    1. A comparison of animal personality and coping styles in the red junglefowl
    Open this publication in new window or tab >>A comparison of animal personality and coping styles in the red junglefowl
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    2017 (English)In: Animal Behaviour, ISSN 0003-3472, E-ISSN 1095-8282, Vol. 130, p. 209-220Article in journal (Refereed) Published
    Abstract [en]

    There is an increased focus in biology on consistent behavioural variation. Several terms are used to describe this variation, including animal personality and coping style. Both terms describe between individual consistency in behavioural variation; however, they differ in the behavioural assays typically used, the expected distribution of response variables, and whether they incorporate variation in behavioural flexibility. Despite these differences, the terms are often used interchangeably. We conducted experiments using juvenile and adult red junglefowl, Gallus gallus, as subjects to explore the degree to which animal personality and coping styles overlap. We demonstrate that animal personality and coping styles can be described in this species, and that shyer individuals had more flexible responses, as expected for coping styles. Behavioural responses from both personality and coping style assays had continuous distributions, and were not clearly separated into two types. Behavioural traits were not correlated and, hence, there was no evidence of a behavioural syndrome. Further, behavioural responses obtained in personality assays did not correlate with those from coping style tests. Animal personality and coping styles are therefore not synonymous in the red junglefowl. We suggest that the terms animal personality and coping style are not equivalent and should not be used interchangeably. (C) 2017 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.

    Place, publisher, year, edition, pages
    ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD, 2017
    Keywords
    boldness e; xploration; Gallus gallus; individual differences; stress coping
    National Category
    Behavioral Sciences Biology
    Identifiers
    urn:nbn:se:liu:diva-139903 (URN)10.1016/j.anbehav.2017.06.024 (DOI)000406939400022 ()
    Note

    Funding Agencies|Royal Swedish Academy of Sciences; Swedish Research Council; ERC (Advanced Research Grant Genewell); LiU programme for Future research leaders; Swedish research council Formas

    Available from: 2017-08-24 Created: 2017-08-24 Last updated: 2017-09-13
    2. Early experience affects adult personality in the red junglefowl: a role for cognitive stimulation?
    Open this publication in new window or tab >>Early experience affects adult personality in the red junglefowl: a role for cognitive stimulation?
    Show others...
    2017 (English)In: Behavioural Processes, ISSN 0376-6357, E-ISSN 1872-8308, Vol. 134, p. 78-86Article in journal (Refereed) Published
    Abstract [en]

    Despite intense research efforts, biologists are still puzzled by the existence of animal personality. While recent studies support a link between cognition and personality, the directionality of this relationship still needs to be clarified. Early-life experiences can affect adult behaviour, and among these, cognitive stimulation has been suggested theoretically to influence personality. Yet, the influence of early cognitive stimulation has rarely been explored in empirical investigations of animal behaviour and personality. We investigated the effect of early cognitive stimulation on adult personality in the red junglefowl (Gallus gallus). To this end, we assessed adult behaviour across a number of personality assays and compared behaviour of individuals previously exposed to a series of learning tasks as chicks, with that of control individuals lacking this experience. We found that individuals exposed to early stimulation as adults were more vigilant and performed fewer escape attempts in personality assays. Other behaviours describing personality traits in the fowl were not affected. We conclude that our results support the hypothesis that early stimulation can affect aspects of adult behaviour and personality, suggesting a hitherto underappreciated causality link between cognition and personality. Future research should aim to confirm these findings and resolve their underlying dynamics and proximate mechanisms.

    Place, publisher, year, edition, pages
    Elsevier, 2017
    Keywords
    Developmental plasticity, Boldness, Exploration, Gallus gallus, Juvenile learning, Neophobia, Vigilance
    National Category
    Behavioral Sciences Biology
    Identifiers
    urn:nbn:se:liu:diva-131304 (URN)10.1016/j.beproc.2016.06.003 (DOI)000392893600011 ()27329431 (PubMedID)
    Available from: 2016-09-13 Created: 2016-09-13 Last updated: 2018-03-28Bibliographically approved
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    The relationship between personality and cognitionin the fowl, Gallus gallus
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  • 11474.
    Zidar, Josefina
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biology. Linköping University, Faculty of Science & Engineering.
    Balogh, Alexandra
    Linköping University, Department of Physics, Chemistry and Biology, Biology. Linköping University, The Institute of Technology.
    Favati, Anna
    Stockholm University, Sweden.
    Jensen, Per
    Linköping University, Department of Physics, Chemistry and Biology, Biology. Linköping University, Faculty of Science & Engineering.
    Leimar, Olof
    Stockholm University, Sweden.
    Lovlie, Hanne
    Linköping University, Department of Physics, Chemistry and Biology, Biology. Linköping University, Faculty of Science & Engineering.
    A comparison of animal personality and coping styles in the red junglefowl2017In: Animal Behaviour, ISSN 0003-3472, E-ISSN 1095-8282, Vol. 130, p. 209-220Article in journal (Refereed)
    Abstract [en]

    There is an increased focus in biology on consistent behavioural variation. Several terms are used to describe this variation, including animal personality and coping style. Both terms describe between individual consistency in behavioural variation; however, they differ in the behavioural assays typically used, the expected distribution of response variables, and whether they incorporate variation in behavioural flexibility. Despite these differences, the terms are often used interchangeably. We conducted experiments using juvenile and adult red junglefowl, Gallus gallus, as subjects to explore the degree to which animal personality and coping styles overlap. We demonstrate that animal personality and coping styles can be described in this species, and that shyer individuals had more flexible responses, as expected for coping styles. Behavioural responses from both personality and coping style assays had continuous distributions, and were not clearly separated into two types. Behavioural traits were not correlated and, hence, there was no evidence of a behavioural syndrome. Further, behavioural responses obtained in personality assays did not correlate with those from coping style tests. Animal personality and coping styles are therefore not synonymous in the red junglefowl. We suggest that the terms animal personality and coping style are not equivalent and should not be used interchangeably. (C) 2017 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.

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  • 11475.
    Zidar, Josefina
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biology. Linköping University, Faculty of Science & Engineering.
    Balogh, Alexandra
    Linköping University, Department of Physics, Chemistry and Biology, Biology. Linköping University, Faculty of Science & Engineering. Stockholm Univ, Sweden.
    Favati, Anna
    Stockholm Univ, Sweden.
    Jensen, Per
    Linköping University, Department of Physics, Chemistry and Biology, Biology. Linköping University, Faculty of Science & Engineering.
    Leimar, Olof
    Stockholm Univ, Sweden.
    Sorato, Enrico
    Linköping University, Department of Physics, Chemistry and Biology, Biology. Linköping University, Faculty of Science & Engineering.
    Lovlie, Hanne
    Linköping University, Department of Physics, Chemistry and Biology, Biology. Linköping University, Faculty of Science & Engineering.
    The relationship between learning speed and personality is age- and task-dependent in red junglefowl2018In: Behavioral Ecology and Sociobiology, ISSN 0340-5443, E-ISSN 1432-0762, Vol. 72, no 10, article id UNSP 168Article in journal (Refereed)
    Abstract [en]

    Cognition is fundamental to animals lives and an important source of phenotypic variation. Nevertheless, research on individual variation in animal cognition is still limited. Further, although individual cognitive abilities have been suggested to be linked to personality (i.e., consistent behavioral differences among individuals), few studies have linked performance across multiple cognitive tasks to personality traits. Thus, the interplays between cognition and personality are still unclear. We therefore investigated the relationships between an important aspect of cognition, learning, and personality, by exposing young and adult red junglefowl (Gallus gallus) to multiple learning tasks (discriminative, reversal, and spatial learning) and personality assays (novel arena, novel object, and tonic immobility). Learning speed was not correlated across learning tasks, and learning speed in discrimination and spatial learning tasks did not co-vary with personality. However, learning speed in reversal tasks was associated with individual variation in exploration, and in an age-dependent manner. More explorative chicks learned the reversal task faster than less explorative ones, while the opposite association was found for adult females (learning speed could not be assayed in adult males). In the same reversal tasks, we also observed a sex difference in learning speed of chicks, with females learning faster than males. Our results suggest that the relationship between cognition and personality is complex, as shown by its task- and age-dependence, and encourage further investigation of the causality and dynamics of this relationship.Significance statementIn the ancestor of todays chickens, the red junglefowl, we explored how personality and cognition relate by exposing both chicks and adults to several learning tasks and personality assays. Our birds differed in personality and learning speed, while fast learners in one task did not necessarily learn fast in another (i.e., there were no overall smarter birds). Exploration correlated with learning speed in the more complex task of reversal learning: faster exploring chicks, but slower exploring adult females, learned faster, compared to less explorative birds. Other aspects of cognition and personality did not correlate. Our results suggest that cognition and personality are related, and that the relationship can differ depending on task and age of the animal.

  • 11476.
    Zidar, Josefina
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biology. Linköping University, Faculty of Science & Engineering.
    Balogh, Alexandra
    Linköping University, Department of Physics, Chemistry and Biology, Biology. Linköping University, Faculty of Science & Engineering. Stockholm Univ, Sweden.
    Leimar, Olof
    Stockholm Univ, Sweden.
    Lovlie, Hanne
    Linköping University, Department of Physics, Chemistry and Biology, Biology. Linköping University, Faculty of Science & Engineering.
    Generalization of learned preferences covaries with behavioral flexibility in red junglefowl chicks2019In: Behavioral Ecology, ISSN 1045-2249, E-ISSN 1465-7279, Vol. 30, no 5, p. 1375-1381Article in journal (Refereed)
    Abstract [en]

    The relationship between animal cognition and consistent among-individual behavioral differences (i.e., behavioral types, animal personality, or coping styles), has recently received increased research attention. Focus has mainly been on linking different behavioral types to performance in learning tasks. It has been suggested that behavioral differences could influence also how individuals use previously learnt information to generalize about new stimuli with similar properties. Nonetheless, this has rarely been empirically tested. Here, we therefore explore the possibility that individual variation in generalization is related to variation in behavioral types in red junglefowl chicks (Gallus gallus). We show that more behaviorally flexible chicks have a stronger preference for a novel stimulus that is intermediate between 2 learnt positive stimuli compared to more inflexible chicks. Thus, more flexible and inflexible chicks differ in how they generalize. Further, behavioral flexibility correlates with fearfulness, suggesting a coping style, supporting that variation in generalization is related to variation in behavioral types. How individuals generalize affects decision making and responses to novel situations or objects, and can thus have a broad influence on the life of an individual. Our results add to the growing body of evidence linking cognition to consistent behavioral differences.

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  • 11477.
    Zidar, Josefina
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biology. Linköping University, Faculty of Science & Engineering.
    Campderrich, Irene
    Department of Animal Environment and Health, Swedish University of Agricultural Sciences, Uppsala, Sweden; Neiker-Tecnalia, Department of Animal Production, Vitoria-Gasteiz, Spain.
    Jansson, Emilie
    Linköping University, Department of Physics, Chemistry and Biology, Biology. Linköping University, Faculty of Science & Engineering.
    Wichman, Anette
    Department of Animal Environment and Health, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Winberg, Svante
    Department of Neuroscience, Uppsala Biomedical Centre BMC, Uppsala University, Uppsala, Sweden.
    Keeling, Linda
    Department of Animal Environment and Health, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Løvlie, Hanne
    Linköping University, Department of Physics, Chemistry and Biology, Biology. Linköping University, Faculty of Science & Engineering.
    Environmental complexity buffers against stress-induced negative judgement bias in female chickens2018In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 8, no 5404Article in journal (Refereed)
    Abstract [en]

    Cognitive processes are often biased by emotions. In humans, affective disorders are accompanied by pessimistic judgement, while optimistic judgement is linked to emotional stability. Similar to humans, animals tend to interpret ambiguous stimuli negatively after experiencing stressful events, although the long-lasting impact on judgement bias has rarely been investigated. We measure judgement bias in female chicks (Gallus gallus domesticus) after exposure to cold stress, and before and after exposure to additional unpredictable stressors. Additionally, we explore if brain monoamines can explain differences in judgement bias. Chicks exposed to cold stress did not differ in judgement bias compared to controls, but showed sensitivity to additional stressors by having higher motivation for social reinstatement. Environmental complexity reduced stress-induced negative judgement bias, by maintaining an optimistic bias in individuals housed in complex conditions even after stress exposure. Moreover, judgement bias was related to dopamine turnover rate in mesencephalon, with higher activity in individuals that had a more optimistic response. These results demonstrate that environmental complexity can buffer against negative effects of additive stress and that dopamine relates to judgement bias in chicks. These results reveal that both internal and external factors can mediate emotionally biased judgement in animals, thus showing similarities to findings in humans.

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  • 11478.
    Zidar, Josefina
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biology. Linköping University, The Institute of Technology.
    Løvlie, Hanne
    Linköping University, Department of Physics, Chemistry and Biology, Biology. Linköping University, The Institute of Technology.
    Fåglars Luktsinne2012In: Fauna och flora : populär tidskrift för biologi, ISSN 0014-8903, Vol. 107, no 4, p. 26-29Article in journal (Other (popular science, discussion, etc.))
  • 11479.
    Zidar, Josefina
    et al.
    Stockholm University, Sweden.
    Løvlie, Hanne
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology. Stockholm University, Stockholm, Sweden.
    Scent of the enemy: behavioural responses to predator faecal odour in the fowl2012In: Animal Behaviour, ISSN 0003-3472, E-ISSN 1095-8282, Vol. 84, no 3, p. 547-554Article in journal (Refereed)
    Abstract [en]

    Chemical communication is used by diverse organisms in a variety of contexts and can have strong fitness consequences for the individuals involved. However, despite the extensive use of birds as models for many research areas in biology, avian olfaction has been poorly investigated. Studies on bird species that lack well-developed olfactory organs and those investigating responses to predator odours are particularly scarce. We investigated behavioural responses of the domestic fowl, Gallus gallus domesticus, a ground-living species with intermediate olfactory bulb size, to several predator and nonpredator faecal odours. We found that the birds spent less time foraging and were more vigilant when exposed to predator faecal odour compared with nonpredator faecal odour. Individuals showed a similar response when exposed to increased amounts of faeces. Taken together, our results demonstrate that domestic fowl can distinguish between herbivore and predator faecal odour, and respond to predator olfactory cues alone, without prior experience. Our results have implications for the understanding of predator-prey interactions and responses to olfactory cues in general, and for chemical communication in avian species more specifically.

  • 11480.
    Zidar, Josefina
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biology. Linköping University, Faculty of Science & Engineering.
    Sorato, Enrico
    Linköping University, Department of Physics, Chemistry and Biology, Biology. Linköping University, Faculty of Science & Engineering.
    Malmqvist, Ann-Marie
    Linköping University, Department of Physics, Chemistry and Biology, Biology. Linköping University, Faculty of Science & Engineering.
    Jansson, Emelie
    Linköping University, Department of Physics, Chemistry and Biology, Biology. Linköping University, Faculty of Science & Engineering.
    Rosher, Charlotte
    Linköping University, Department of Physics, Chemistry and Biology, Biology. Linköping University, Faculty of Science & Engineering. Faculty of Life Sciences, University of Manchester, Manchester, UK.
    Jensen, Per
    Linköping University, Department of Physics, Chemistry and Biology, Biology. Linköping University, Faculty of Science & Engineering.
    Favati, Anna
    Department of Zoology, Stockholm University, Stockholm, Sweden.
    Løvlie, Hanne
    Linköping University, Department of Physics, Chemistry and Biology, Biology. Linköping University, Faculty of Science & Engineering.
    Early experience affects adult personality in the red junglefowl: a role for cognitive stimulation?2017In: Behavioural Processes, ISSN 0376-6357, E-ISSN 1872-8308, Vol. 134, p. 78-86Article in journal (Refereed)
    Abstract [en]

    Despite intense research efforts, biologists are still puzzled by the existence of animal personality. While recent studies support a link between cognition and personality, the directionality of this relationship still needs to be clarified. Early-life experiences can affect adult behaviour, and among these, cognitive stimulation has been suggested theoretically to influence personality. Yet, the influence of early cognitive stimulation has rarely been explored in empirical investigations of animal behaviour and personality. We investigated the effect of early cognitive stimulation on adult personality in the red junglefowl (Gallus gallus). To this end, we assessed adult behaviour across a number of personality assays and compared behaviour of individuals previously exposed to a series of learning tasks as chicks, with that of control individuals lacking this experience. We found that individuals exposed to early stimulation as adults were more vigilant and performed fewer escape attempts in personality assays. Other behaviours describing personality traits in the fowl were not affected. We conclude that our results support the hypothesis that early stimulation can affect aspects of adult behaviour and personality, suggesting a hitherto underappreciated causality link between cognition and personality. Future research should aim to confirm these findings and resolve their underlying dynamics and proximate mechanisms.

    Download full text (pdf)
    fulltext
  • 11481.
    Zimdahl Kahlin, Anna
    et al.
    Linköping University, Department of Medical and Health Sciences, Division of Drug Research. Linköping University, Faculty of Medicine and Health Sciences.
    Helander, Sara
    Linköping University, Department of Clinical and Experimental Medicine, Division of Clinical Chemistry. Linköping University, Faculty of Medicine and Health Sciences.
    Skoglund, Karin
    Linköping University, Department of Medical and Health Sciences, Division of Drug Research. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Business support and Development, Department of Health and Care Development.
    Söderkvist, Peter
    Linköping University, Department of Clinical and Experimental Medicine, Division of Cell Biology. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Diagnostics, Clinical genetics.
    Mårtensson, Lars-Göran
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Lindqvist Appell, Malin
    Linköping University, Department of Medical and Health Sciences, Division of Drug Research. Linköping University, Faculty of Medicine and Health Sciences.
    Comprehensive study of thiopurine methyltransferase genotype, phenotype, and genotype-phenotype discrepancies in Sweden2019In: Biochemical Pharmacology, ISSN 0006-2952, E-ISSN 1356-1839, Vol. 164, p. 263-272Article in journal (Refereed)
    Abstract [en]

    Thiopurines are widely used in the treatment of leukemia and inflammatory bowel diseases. Thiopurine metabolism varies among individuals because of differences in the polymorphic enzyme thiopurine methyltransferase (TPMT, EC 2.1.1.67), and to avoid severe adverse reactions caused by incorrect dosing it is recommended that the patients TPMT status be determined before the start of thiopurine treatment. This study describes the concordance between genotyping for common TPMT alleles and phenotyping in a Swedish cohort of 12,663 patients sampled before or during thiopurine treatment. The concordance between TPMT genotype and enzyme activity was 94.5%. Compared to the genotype, the first measurement of TPMT enzyme activity was lower than expected for 4.6% of the patients. Sequencing of all coding regions of the TPMT gene in genotype/phenotype discrepant individuals led to the identification of rare and novel TPMT alleles. Fifteen individuals (0.1%) with rare or novel genotypes were identified, and three TPMT alleles (TPMT*42, *43, and *44) are characterized here for the first time. These 15 patients would not have been detected as carrying a deviating TPMT genotype if only genotyping of the most common TPMT variants had been performed. This study highlights the benefit of combining TPMT genotype and phenotype determination in routine testing. More accurate dose recommendations can be made, which might decrease the number of adverse reactions and treatment failures during thiopurine treatment.

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  • 11482.
    Zimmerman, Rosa
    et al.
    University of Buenos Aires.
    Broitman, Esteban
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology. University of Buenos Aires.
    Aplicaciones de las Peliculas Delgadas en Microelectronica1986In: Revista Telegrafica Electronica, ISSN 0035-0516, Vol. 75, no 880, p. 2052-2056Article in journal (Refereed)
    Abstract [es]

    En este articulo se presenta una reseña acerca del uso de las peliculas delgadas en microelectronica con especial enfasis en las peliculas resistivas. Se detallan las propiedades electricas de la aleacion niquel-cromo.

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  • 11483.
    Zimmermann, F.
    et al.
    TU Bergakad Freiberg, Germany.
    Beyer, Franziska
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Gaertner, G.
    TU Bergakad Freiberg, Germany.
    Roeder, C.
    TU Bergakad Freiberg, Germany.
    Nguyen, Son Tien
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Vesela, D.
    Research Centre Rez, Czech Republic.
    Lorincik, J.
    Research Centre Rez, Czech Republic.
    Hofmann, P.
    NaMLab gGmbH, Germany.
    Krupinski, M.
    NaMLab gGmbH, Germany.
    Mikolajick, T.
    NaMLab gGmbH, Germany; Technical University of Dresden, Germany.
    Habel, F.
    Freiberger Compound Mat GmbH, Germany.
    Leibiger, G.
    Freiberger Compound Mat GmbH, Germany.
    Heitmann, J.
    TU Bergakad Freiberg, Germany.
    Origin of orange color in nominally undoped HVPE GaN crystals2017In: Optical materials (Amsterdam), ISSN 0925-3467, E-ISSN 1873-1252, Vol. 70, p. 127-130Article in journal (Refereed)
    Abstract [en]

    In this article we investigated unintentionally doped (UID) GaN grown by hydride vapor phase epitaxy (HVPE) with respect to point defects and impurity concentration. The samples were orange tinted to different extent. Optical analysis was performed by micro-photoluminescence and absorption spectroscopy. Absorption measurements revealed an absorption peak at 1.5 eV related to an internal transition in Mn3+ impurities and a second band with low energy onset at 1.9 eV, both increasing with the extent of orange color. Electron paramagnetic resonance investigations showed the presence of Mn2+ and Fe3+ in the colored crystals. The overall impurity concentration was verified by secondary ion mass spectrometry. Orange tint is associated with an increase of transition metal contamination, especially Mn. Based on these observations we suggest that the orange coloring in the investigated UID HVPE GaN samples is caused by the presence of Mn impurities. (C) 2017 Elsevier B.V. All rights reserved.

  • 11484.
    Zimmermann, U
    et al.
    Royal Inst Technol, Dept Microelect & Informat Technol, SE-16440 Kista, Sweden Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden.
    Osterman, J
    Royal Inst Technol, Dept Microelect & Informat Technol, SE-16440 Kista, Sweden Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden.
    Zhang, J
    Henry, Anne
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Hallen, A
    Royal Inst Technol, Dept Microelect & Informat Technol, SE-16440 Kista, Sweden Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden.
    Electrical characterization of high-voltage 4H-SiC diodes on high-temperature CVD-grown epitaxial layers2002In: Materials Science Forum, Vols. 389-393, 2002, Vol. 389-3, p. 1285-1288Conference paper (Refereed)
    Abstract [en]

    High-temperature chemical vapour deposition (HTCVD) in a vertical chimney reactor was used to grow thick low-doped epitaxial layers of 4H silicon carbide. These layers were used as drift layers in a combined process to manufacture both bipolar and unipolar high-voltage diodes. The resulting diodes were characterized electrically in order to gain knowledge about the electric quality of the HTCVD epitaxial layers to assess the high-voltage properties of this material.

  • 11485.
    Zocco, A.
    et al.
    University of Lecce, Physics Department and Istituto Nazionale Fisica della Materia, 73100 Lecce, Italy.
    Perrone, A.
    University of Lecce, Physics Department and Istituto Nazionale Fisica della Materia, 73100 Lecce, Italy.
    Broitman, Esteban
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Czigany, Zs.
    Divisione Fisica Chimica delle Superfici ed Interfacce, ITC-IRST, 38050 Povo Trento, Italy.
    Hultman, Lars
    Divisione Fisica Chimica delle Superfici ed Interfacce, ITC-IRST, 38050 Povo Trento, Italy.
    Anderle, M.
    Divisione Fisica Chimica delle Superfici ed Interfacce, ITC-IRST, 38050 Povo Trento, Italy.
    Laidani, N.
    Mechanical and tribological properties of CNx films deposited by reactive pulsed laser ablation2002In: Diamond and related materials, ISSN 0925-9635, E-ISSN 1879-0062, Vol. 11, no 1, p. 98-104Article in journal (Refereed)
    Abstract [en]

    We report the tribological, mechanical, structural and compositional characteristics of CNx films deposited by excimer laser (XeCl, ? = 308 nm, TFWHM = 30 ns) ablation of a graphite target in N2 atmosphere. The influence of growth conditions on structural, morphological, tribological and mechanical properties of the CNx films has been examined by X-ray Photoelectron Spectroscopy (XPS), Transmission and Scanning Electron Microscopy (TEM and SEM, respectively), nanoindentation measurements and ball-on-disk tests. All the as-deposited films have a microstructure consisting of nanometer-sized graphitic clusters in an amorphous matrix. The stresses of the films are tensile or compressive depending on the deposition conditions. Friction coefficients of the films, deduced by high speed steel balls, increase with laser fluence and nitrogen pressure from 0.12 to 0.14. Friction is thus, lower than what has been reported in literature for CNx films. © 2002 Elsevier Science B.V. All rights reserved.

  • 11486. Zolnai, Z
    et al.
    Nguyen, Son Tien
    Linköping University, Department of Physics, Chemistry and Biology.
    Hallin, Christer
    Linköping University, Department of Physics, Chemistry and Biology.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology.
    Annealing behavior of the carbon vacancy in electron-irradiated 4H-SiC2004In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 96, no 4, p. 2406-2408Article in journal (Refereed)
    Abstract [en]

    The annealing behavior of the positively charged carbon vacancy in electron-irradiated 4H-SiC was studied. Electron paramagnetic resonance was used for the purpose of analysis. It was found that around 1000 °C, the EPR signal of the defect starts decreasing. Clear ligand hyperfine structure was also observed after annealing at 1350 °C. Results show that the EI6 center may be the positively charged carbon vacancy at the hexagonal lattice site of 4H-SiC.

  • 11487. Zolnai, Z.
    et al.
    Nguyen, Son Tien
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Magnusson, Björn
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Hallin, Christer
    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.
    Annealing behaviour of vacancy- and antisite-related defects in electron-irradiated 4H-SiC2004In: Mater. Sci. Forum, Vol. 457-460, Trans Tech Publications Inc. , 2004, p. 473-Conference paper (Refereed)
  • 11488.
    Zondaka, Zane
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Sensor and Actuator Systems. Linköping University, Faculty of Science & Engineering.
    Zhong, Yong
    Linköping University, Department of Physics, Chemistry and Biology, Sensor and Actuator Systems. Linköping University, Faculty of Science & Engineering.
    Jager, Edwin
    Linköping University, Department of Physics, Chemistry and Biology, Sensor and Actuator Systems. Linköping University, Faculty of Science & Engineering.
    Development of hybrid material soft microactuators2016Conference paper (Other academic)
  • 11489.
    Zondaka, Zane
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Sensor and Actuator Systems. Linköping University, Faculty of Science & Engineering.
    Zhong, Yong
    Linköping University, Department of Physics, Chemistry and Biology, Sensor and Actuator Systems. Linköping University, Faculty of Science & Engineering.
    Jager, Edwin
    Linköping University, Department of Physics, Chemistry and Biology, Sensor and Actuator Systems. Linköping University, Faculty of Science & Engineering.
    Development of hybrid material soft microactuators2016Conference paper (Other academic)
  • 11490.
    Zotti, G.
    et al.
    Istituto CNR l'Energetica Interfasi, C.o Stati Uniti 4, 35127 Padova, Italy.
    Zecchin, S.
    Istituto CNR l'Energetica Interfasi, C.o Stati Uniti 4, 35127 Padova, Italy.
    Schiavon, G.
    Istituto CNR l'Energetica Interfasi, C.o Stati Uniti 4, 35127 Padova, Italy.
    Louwet, F.
    R and D Materials Research, Chemistry Department, Agfa Gevaert N.V., Septelaan 27, B-2640 Mortsel, Belgium.
    Groenendaal, L.
    R and D Materials Research, Chemistry Department, Agfa Gevaert N.V., Septelaan 27, B-2640 Mortsel, Belgium.
    Crispin, Xavier
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
    Osikowicz, Wojciech
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Salaneck, William R
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Fahlman, Mats
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Electrochemical and XPS studies toward the role of monomeric and polymeric sulfonate counterions in the synthesis, composition, and properties of poly(3,4-ethylenedioxythiophene)2003In: Macromolecules, ISSN 0024-9297, E-ISSN 1520-5835, Vol. 36, no 9, p. 3337-3344Article in journal (Refereed)
    Abstract [en]

    Electrochemically prepared poly(3,4-ethylenedioxythiophene) (PEDT) poly(styrenesulfonate) (PSS), produced from acidic (PSSH) and basic (PSSNa) PSS, was characterized by cyclic voltammetry CV, UV-vis spectroscopy, in situ conductivity, and XPS spectroscopy and was compared with electrochemically prepared PEDT/tosylate and chemically prepared PEDT/PSS. CV analysis shows that the polymer synthesis is strongly affected by the nucleophilic character of the counteranion. Although CV and UV-vis spectroscopy show that the structure and degree of polymerization (oligomeric, ca. 10 EDT units) of the PEDT backbone is the same for all polymers, XPS is able to explain the different conductivity values for these materials (ranging from 1 S cm-1 for PEDT/PSSNa to 400-450 S cm-1 for PEDT/tosylate) based on doping level and composition. In particular, critical results are observed to be the ratios between sulfonate and thiophene units in the polymers: the higher the PEDT concentration, the higher the conductivity. XPS also explains by solvent-induced nanometer-scale segregation between PEDT/PSS and excess PSS particles the often reported conductivity enhancement of chemically prepared PEDT/PSS upon treatment with polar solvents.

  • 11491.
    Zou, Wei
    et al.
    Nanjing Tech Univ, Peoples R China; Nanjing Tech Univ, Peoples R China.
    Li, Renzhi
    Nanjing Tech Univ, Peoples R China; Nanjing Tech Univ, Peoples R China.
    Zhang, Shuting
    Nanjing Tech Univ, Peoples R China; Nanjing Tech Univ, Peoples R China.
    Liu, Yunlong
    Nanjing Tech Univ, Peoples R China; Nanjing Tech Univ, Peoples R China; Liaocheng Univ, Peoples R China.
    Wang, Nana
    Nanjing Tech Univ, Peoples R China; Nanjing Tech Univ, Peoples R China.
    Cao, Yu
    Nanjing Tech Univ, Peoples R China; Nanjing Tech Univ, Peoples R China.
    Miao, Yanfeng
    Nanjing Tech Univ, Peoples R China; Nanjing Tech Univ, Peoples R China.
    Xu, Mengmeng
    Nanjing Tech Univ, Peoples R China; Nanjing Tech Univ, Peoples R China.
    Guo, Qiang
    Nanjing Tech Univ, Peoples R China; Nanjing Tech Univ, Peoples R China.
    Di, Dawei
    Univ Cambridge, England.
    Zhang, Li
    Nanjing Tech Univ, Peoples R China; Nanjing Tech Univ, Peoples R China.
    Yi, Chang
    Nanjing Tech Univ, Peoples R China; Nanjing Tech Univ, Peoples R China.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Friend, Richard H.
    Univ Cambridge, England.
    Wang, Jianpu
    Nanjing Tech Univ, Peoples R China; Nanjing Tech Univ, Peoples R China.
    Huang, Wei
    Nanjing Tech Univ, Peoples R China; Nanjing Tech Univ, Peoples R China; Nanjing Univ Posts and Telecommun, Peoples R China; Nanjing Univ Posts and Telecommun, Peoples R China; Northwestern Polytech Univ, Peoples R China.
    Minimising efficiency roll-off in high-brightness perovskite light-emitting diodes2018In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 9, article id 608Article in journal (Refereed)
    Abstract [en]

    Efficiency roll-off is a major issue for most types of light-emitting diodes (LEDs), and its origins remain controversial. Here we present investigations of the efficiency roll-off in perovskite LEDs based on two-dimensional layered perovskites. By simultaneously measuring electroluminescence and photoluminescence on a working device, supported by transient photoluminescence decay measurements, we conclude that the efficiency roll-off in perovskite LEDs is mainly due to luminescence quenching which is likely caused by non-radiative Auger recombination. This detrimental effect can be suppressed by increasing the width of quantum wells, which can be easily realized in the layered perovskites by tuning the ratio of large and small organic cations in the precursor solution. This approach leads to the realization of a perovskite LED with a record external quantum efficiency of 12.7%, and the efficiency remains to be high, at approximately 10%, under a high current density of 500 mA cm(-2).

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  • 11492.
    Zou, Yatao
    et al.
    Soochow Univ, Peoples R China; Soochow Univ, Peoples R China.
    Ban, Muyang
    Soochow Univ, Peoples R China; Soochow Univ, Peoples R China.
    Yang, Yingguo
    Chinese Acad Sci, Peoples R China.
    Bai, Sai
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Wu, Chen
    Soochow Univ, Peoples R China; Soochow Univ, Peoples R China.
    Han, Yujie
    Soochow Univ, Peoples R China; Soochow Univ, Peoples R China.
    Wu, Tian
    Soochow Univ, Peoples R China; Soochow Univ, Peoples R China.
    Tan, Yeshu
    Soochow Univ, Peoples R China; Soochow Univ, Peoples R China.
    Huang, Qi
    Soochow Univ, Peoples R China; Soochow Univ, Peoples R China.
    Gao, Xingyu
    Chinese Acad Sci, Peoples R China.
    Song, Tao
    Soochow Univ, Peoples R China; Soochow Univ, Peoples R China.
    Zhang, Qiao
    Soochow Univ, Peoples R China; Soochow Univ, Peoples R China.
    Sun, Baoquan
    Soochow Univ, Peoples R China; Soochow Univ, Peoples R China.
    Boosting Perovskite Light-Emitting Diode Performance via Tailoring Interfacial Contact2018In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 10, no 28, p. 24320-24326Article in journal (Refereed)
    Abstract [en]

    Solution-processed perovskite light-emitting diodes (LEDs) have attracted wide attention in the past several years. However, the overall efficiency and stability of perovskite-based LEDs remain inferior to those of organic or quantum dot LEDs. Nonradiative charge recombination and the unbalanced charge injection are two critical factors that limit the device efficiency and operational stability of perovskite LEDs. Here, we develop a strategy to modify the interface between the hole transport layer and the perovskite emissive layer with an amphiphilic conjugated polymer of poly[(9,9-bis(3-(N,N-dimethylamino)propy1)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] (PFN). We show evidences that PFN improves the quality of the perovskite film, which effectively suppresses nonradiative recombination. By further improving the charge injection balance rate, a green perovskite LED with a champion current efficiency of 45.2 cd/A, corresponding to an external quantum efficiency of 14.4%, is achieved. In addition, the device based on the PFN layer exhibits improved operational lifetime. Our work paves a facile way for the development of efficient and stable perovskite LEDs.

  • 11493.
    Zou, Yatao
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering. Soochow Univ, Peoples R China.
    Xu, Hao
    Soochow Univ, Peoples R China.
    Li, Siying
    Soochow Univ, Peoples R China.
    Song, Tao
    Soochow Univ, Peoples R China.
    Kuai, Liang
    Soochow Univ, Peoples R China.
    Bai, Sai
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Sun, Baoquan
    Soochow Univ, Peoples R China.
    Spectral-Stable Blue Emission from Moisture-Treated Low-Dimensional Lead Bromide-Based Perovskite Films2019In: ACS Photonics, E-ISSN 2330-4022, Vol. 6, no 7, p. 1728-1735Article in journal (Refereed)
    Abstract [en]

    Highly efficient light-emitting diodes (LEDs) based on metal halide perovskites with green, red, and near-infrared electro-luminescence have been widely demonstrated. However, the development of their blue counterparts is still hampered due to the difficult deposition of efficient and spectral-stable blue-emitting active layers. Here, we report a facile and general approach that uses a moisture treatment in combination with the precursor stoichiometry engineering for the fabrication of efficient and color stable blue-emitting perovskite films. We find that, with a short-term moisture exposure, light emission from Ruddlesden Popper lead bromide-based perovskite films exhibit a continuous blue-shift from 512 to 475 nm through incorporating excess CsBr in the precursors. In addition, we observe that the formed Cs4PbBr6 phase under CsBr-rich condition is favorable to stabilize the blue emission of the resulting films. The corresponding blue-emitting perovskite films exhibit a photoluminescence quantum efficiency of over 20%, delivering sky-blue perovskite LEDs with no change in the light emission even under high voltage. Our strategy provides an alternative way for realizing efficient and spectrally stable active layers for the further development of blue-emitting perovskite LEDs.

  • 11494.
    Zoulis, G.
    et al.
    CNRS, Montpellier, France.
    Sun, Jianwu
    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.
    Lorenzzi, J.
    Laboratoire des Multimateriaux et Interfaces, University Claude Bernard Lyon 1, Villeurbanne, France.
    Peyre, H.
    Université Montpellier 2, France.
    Syväjärvi, Mikael
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Ferro, G.
    Laboratoire des Multimateriaux et Interfaces, University Claude Bernard Lyon 1, Villeurbanne, France.
    Juillaguet, S.
    Université Montpellier 2, France.
    Yakimova, Rositza
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Camassel, J.
    CNRS, Montpellier, France .
    Seeding layer influence on the low temperature photoluminescence intensity of 3C-SiC grown on 6H-SiC by sublimation epitaxy2012In: HETEROSIC and WASMPE 2011 / [ed] Daniel Alquier, Trans Tech Publications Inc., 2012, Vol. 711, p. 149-153Conference paper (Refereed)
    Abstract [en]

    We report on n-type 3C-SiC samples grown by sublimation epitaxy. We focus on the low temperature photoluminescence intensity and show that the presence of a first conversion layer, grown at low temperature, is not only beneficial to improve the homogeneity of the polytype conversion but, also, to the LTPL signal intensity. From the use of a simple model, we show that this comes from a reduced density of non-radiative recombination centers.

  • 11495.
    Zoulis, Georgios
    et al.
    Groupe d’Etudes des Semiconducteurs, Université Montpellier 2 and CNRS, cc 074‐GES, 34095 Montpellier Cedex 5, France.
    Sun, Jian Wu
    Groupe d’Etudes des Semiconducteurs, Université Montpellier 2 and CNRS, cc 074‐GES, 34095 Montpellier Cedex 5, France.
    Beshkova, Milena
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Vasiliauskas, Remigijus
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Juillaguet, S.
    Groupe d’Etudes des Semiconducteurs, Université Montpellier 2 and CNRS, cc 074‐GES, 34095 Montpellier Cedex 5, France.
    Peyre, H.
    Groupe d’Etudes des Semiconducteurs, Université Montpellier 2 and CNRS, cc 074‐GES, 34095 Montpellier Cedex 5, France.
    Syväjärvi, Mikael
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Yakimova, Rositsa
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Camassel, J.
    Groupe d’Etudes des Semiconducteurs, Université Montpellier 2 and CNRS, cc 074‐GES, 34095 Montpellier Cedex 5, France.
    Investigation of Low Doped n-Type and p-Type 3C-SiC Layers Grown on 6H-SiC Substrates by Sublimation Epitaxy2010In: Silicon Carbide and Related Materials 2009, 2010, Vol. 645, p. 179-182Conference paper (Refereed)
    Abstract [en]

    Both, n-type and p-type 3C-SiC samples grown on 6H-SiC substrates by sublimation epitaxy have been investigated. From low temperature photoluminescence studies, we demonstrate a low level of residual (n and/or p-type) doping with weak compensation, which is confirmed by secondary ion mass spectroscopy in the case of p-type samples.

  • 11496.
    Zozoulenko, Igor
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
    Sachrajda, A.S.
    Inst. for Microstructural Science, National Research Council, Montreal Road, Ottawa, Ont. K1A 0R6, Canada.
    Gould, C.
    Inst. for Microstructural Science, National Research Council, Montreal Road, Ottawa, Ont. K1A 0R6, Canada, Dépt. de Physique and CRPS, Université de Sherbrooke, Sherbrooke, Que. J1K 2R1, Canada.
    Berggren, Karl-Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics .
    Zawadzki, P.
    Inst. for Microstructural Science, National Research Council, Montreal Road, Ottawa, Ont. K1A 0R6, Canada.
    Feng, Y.
    Inst. for Microstructural Science, National Research Council, Montreal Road, Ottawa, Ont. K1A 0R6, Canada.
    Wasilewski, Z.
    Inst. for Microstructural Science, National Research Council, Montreal Road, Ottawa, Ont. K1A 0R6, Canada.
    Magnetoconductance of a few-electron open quantum dot2000In: Physica. E, Low-Dimensional systems and nanostructures, ISSN 1386-9477, E-ISSN 1873-1759, Vol. 6, no 1, p. 409-413Article in journal (Refereed)
    Abstract [en]

    Magnetoconductance of a small open lateral dot is studied both theoretically and experimentally for the conditions when the dot contains down to approximately 15 electrons. We confirm the existence of a new regime for open dots in which the transport through the structure occurs through individual eigenstates of the corresponding closed dot. In particular, at low magnetic fields the characteristic features in the conductance are related to the underlying eigenspectrum shells. When the number of modes in the leads is reduced more detailed structures within the shells due to single eigenlevels becomes discernible. At higher fields Landau level condensation is evident as well as the crossing of levels collapsing to the different Landau levels.

  • 11497.
    Zubkans, J.
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Lloyd Spetz, Anita
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Sundgren, Hans
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Winquist, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Kleperis, J.
    University of Latvia, Riga, Latvia.
    Lusis, A.
    University of Latvia, Riga, Latvia.
    Lundström, Ingemar
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    In-situ modification of the NOx sensitivity of thin discontinuous platinum films as gates of chemical sensors1995In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 268, no 1-2, p. 140-143Article in journal (Refereed)
    Abstract [en]

    It is shown how chemically sensitive metal-oxide semiconductor field-effect transistors with a thin discontinuous platinum gate can be modified for the detection of NOx. After a pulse of ammonia the sensors show an increased sensitivity to NOx. The threshold voltage shift induced by NOx is opposite to the direction before the ammonia pulse. The threshold voltage now increases due to NOx exposure, while hydrogen, ammonia and hydrocarbons cause a decrease of the threshold voltage. The temperature dependence of the NOx sensitivity suggests that after the ammonia pulse there are two competing polarisation phenomena caused by the interaction between NOx and the sensing surface. The results are of general interest since they indicate how thin sensing layers can be modified after fabrication to promote sensitivity towards specific molecules. Furthermore they shed some new light on the detection mechanisms of thin discontinuous metal gates.

  • 11498.
    Zukauskaite, Agne
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Broitman, Esteban
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Sandström, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Nanoprobe Mechanical and Piezoelectric Characterization of ScxAl1-xN(0001) Thin Films2015In: Physica Status Solidi (a) applications and materials science, ISSN 1862-6300, E-ISSN 1862-6319, Vol. 212, no 3, p. 666-673Article in journal (Refereed)
    Abstract [en]

    Nanoindentation with in-situ electrical characterization was used to characterize piezoelectric scandium aluminum nitride (ScxAl1-xN) thin films with Sc contents up to x=0.3. The films were prepared by reactive magnetron sputtering using Al2O3 substrates with TiN seed layer/bottom electrodes at a substrate temperature of 400 °C. X-ray diffraction shows c-axis oriented wurtzite ScxAl1-xN, where the crystal quality decreases with increasing x. Piezoresponse force microscopy in mapping mode shows a single piezoelectric polarization phase in all samples. The hardness and decreases from 17 GPa in AlN to 11 GPa in Sc0.3Al0.7N, while reduced elastic modulus decreases from 265 GPa to 224 GPa, respectively. Both direct and converse piezoelectric measurements are demonstrated by first applying the load and generating the voltage and later by applying the voltage and measuring film displacement using a conductive boron doped nanoindenter tip. The Sc0.2Al0.8N films exhibit an increase in generated voltage by 15% in comparison to AlN and a correspondingly larger displacement upon applied voltage, comparable to results obtained by double beam interferometry and piezoresponse force microscopy.

     

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  • 11499. Order onlineBuy this publication >>
    Zuo, Guangzheng
    Linköping University, Department of Physics, Chemistry and Biology, Complex Materials and Devices. Linköping University, Faculty of Science & Engineering.
    Doping and Density of States Engineering for Organic Thermoelectrics2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Thermoelectric materials can turn temperature differences directly into electricity. To use this to harvest e.g. waste heat with an efficiency that approaches the Carnot efficiency requires a figure of merit ZT larger than 1. Compared with their inorganic counterparts, organic thermoelectrics (OTE) have numerous advantages, such as low cost, large-area compatibility, flexibility, material abundance and an inherently low thermal conductivity. Therefore, organic thermoelectrics are considered by many to be a promising candidate material system to be used in lower cost and higher efficiency thermoelectric energy conversion, despite record ZT values for OTE currently lying around 0.25.

    A complete organic thermoelectric generator (TEG) normally needs both p-type and n-type materials to form its electric circuit. Molecular doping is an effective way to achieve p- and ntype materials using different dopants, and it is necessary to fundamentally understand the doping mechanism. We developed a simple yet quantitative analytical model and compare it with numerical kinetic Monte Carlo simulations to reveal the nature of the doping effect. The results show the formation of a deep tail in the Gaussian density of states (DOS) resulting from the Coulomb potentials of ionized dopants. It is this deep trap tail that negatively influences the charge carrier mobility with increasing doping concentration. The trends in mobilities and conductivities observed from experiments are in good agreement with the modeling results, for a large range of materials and doping concentrations.

    Having a high power factor PF is necessary for efficient TEG. We demonstrate that the doping method can heavily impact the thermoelectric properties of OTE. In comparison to conventional bulk doping, sequential doping can achieve higher conductivity by preserving the morphology, such that the power factor can improve over 100 times. To achieve TEG with high output power, not only a high PF is needed, but also having a significant active layer thickness is very important. We demonstrate a simple way to fabricate multi-layer devices by sequential doping without significantly sacrificing PF.

    In addition to the application discussed above, harvesting large amounts of heat at maximum efficiency, organic thermoelectrics may also find use in low-power applications like autonomous sensors where voltage is more important than power. A large output voltage requires a high Seebeck coefficient. We demonstrate that density of states (DOS) engineering is an effective tool to increase the Seebeck coefficient by tailoring the positions of the Fermi energy and the transport energy in n- and p-type doped blends of conjugated polymers and small molecules.

    In general, morphology heavily impacts the performance of organic electronic devices based on mixtures of two (or more) materials, and organic thermoelectrics are no exception. We experimentally find that the charge and energy transport is distinctly different in well-mixed and phase separated morphologies, which we interpreted in terms of a variable range hopping model. The experimentally observed trends in conductivity and Seebeck coefficient are reproduced by kinetic Monte Carlo simulations in which the morphology is accounted for.  

    List of papers
    1. Impact of doping on the density of states and the mobility in organic semiconductors
    Open this publication in new window or tab >>Impact of doping on the density of states and the mobility in organic semiconductors
    2016 (English)In: PHYSICAL REVIEW B, ISSN 2469-9950, Vol. 93, no 23, p. 235203-Article in journal (Refereed) Published
    Abstract [en]

    We experimentally investigated conductivity and mobility of poly(3-hexylthiophene) (P3HT) doped with tetrafluorotetracyanoquinodimethane (F(4)TCNQ) for various relative doping concentrations ranging from ultralow (10(-5)) to high (10(-1)) and various active layer thicknesses. Although the measured conductivity monotonously increases with increasing doping concentration, the mobilities decrease, in agreement with previously published work. Additionally, we developed a simple yet quantitative model to rationalize the results on basis of a modification of the density of states (DOS) by the Coulomb potentials of ionized dopants. The DOS was integrated in a three-dimensional (3D) hopping formalism in which parameters such as energetic disorder, intersite distance, energy level difference, and temperature were varied. We compared predictions of our model as well as those of a previously developed model to kinetic Monte Carlo (MC) modeling and found that only the former model accurately reproduces the mobility of MC modeling in a large part of the parameter space. Importantly, both our model and MC simulations are in good agreement with experiments; the crucial ingredient to both is the formation of a deep trap tail in the Gaussian DOS with increasing doping concentration.

    Place, publisher, year, edition, pages
    AMER PHYSICAL SOC, 2016
    National Category
    Other Physics Topics
    Identifiers
    urn:nbn:se:liu:diva-130276 (URN)10.1103/PhysRevB.93.235203 (DOI)000378813800009 ()
    Note

    Funding Agencies|Chinese Scholarship Council (CSC)

    Available from: 2016-08-01 Created: 2016-07-28 Last updated: 2018-08-29
    2. Molecular Doping and Trap Filling in Organic Semiconductor Host-Guest Systems
    Open this publication in new window or tab >>Molecular Doping and Trap Filling in Organic Semiconductor Host-Guest Systems
    Show others...
    2017 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 121, no 14, p. 7767-7775Article in journal (Refereed) Published
    Abstract [en]

    We investigate conductivity and mobility of different hosts mixed with different electron-withdrawing guests in concentrations ranging from ultralow to high. The effect of the guest material on the mobility and conductivity of the host material varies systematically with the guests LUMO energy relative to the host HOMO, in quantitative agreement with a recently developed model. For guests with a LUMO within similar to 0.5 eV of the host HOMO the dominant process governing transport is the competition between the formation of a deep tail in the host DOS and state filling. In other cases, the interaction with the host is dominated by any polar side groups on the guest and changes in the host morphology. For relatively amorphous hosts the latter interaction can lead to a suppression of deep traps, causing a surprising mobility increase by 1-2 orders of magnitude. In order to analyze our data, we developed a simple method to diagnose both the presence and the filling of traps.

    Place, publisher, year, edition, pages
    AMER CHEMICAL SOC, 2017
    National Category
    Condensed Matter Physics
    Identifiers
    urn:nbn:se:liu:diva-137610 (URN)10.1021/acs.jpcc.7b01758 (DOI)000399629000022 ()
    Note

    Funding Agencies|Chinese Scholarship Council (CSC); Knut och Alice Wallenbergs stiftelse (project "Tail of the Sun"); Swedish Research Council; Swedish Research Council Formas; Chalmers Area of Advance Energy

    Available from: 2017-05-22 Created: 2017-05-22 Last updated: 2018-05-14
    3. High Seebeck Coefficient in Mixtures of Conjugated Polymers
    Open this publication in new window or tab >>High Seebeck Coefficient in Mixtures of Conjugated Polymers
    2018 (English)In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 28, no 15, article id 1703280Article in journal (Refereed) Published
    Abstract [en]

    A universal method to obtain record?high electronic Seebeck coefficients is demonstrated while preserving reasonable conductivities in doped blends of organic semiconductors through rational design of the density of states (DOSs). A polymer semiconductor with a shallow highest occupied molecular orbital (HOMO) level?poly(3?hexylthiophene) (P3HT) is mixed with materials with a deeper HOMO (PTB7, TQ1) to form binary blends of the type P3HTx:B1?x (0 ≤ x ≤ 1) that is p?type doped by F4TCNQ. For B = PTB7, a Seebeck coefficient S = 1100 µV K?1 with conductivity σ = 0.3 S m?1 at x = 0.10 is achieved, while for B = TQ1, S = 2000 µV K?1 and σ = 0.03 S m?1 at x = 0.05 is found. Kinetic Monte Carlo simulations with parameters based on experiments show good agreement with the experimental results, confirming the intended mechanism. The simulations are used to derive a design rule for parameter tuning. These results can become relevant for low?power, low?cost applications like (providing power to) autonomous sensors, in which a high Seebeck coefficient translates directly to a proportionally reduced number of legs in the thermogenerator, and hence in reduced fabrication cost and complexity.

    Place, publisher, year, edition, pages
    Wiley-Blackwell, 2018
    Keywords
    conjugated polymers, doping, kinetic Monte Carlo simulations, organic thermoelectrics, Seebeck coefficients
    National Category
    Materials Engineering Physical Sciences
    Identifiers
    urn:nbn:se:liu:diva-147779 (URN)10.1002/adfm.201703280 (DOI)000430101100004 ()
    Conference
    2018/05/14
    Note

    Funding Agencies: Chinese Scholarship Council (CSC)

    Available from: 2018-05-14 Created: 2018-05-14 Last updated: 2018-05-31Bibliographically approved
    4. Range and energetics of charge hopping in organic semiconductors
    Open this publication in new window or tab >>Range and energetics of charge hopping in organic semiconductors
    2017 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 96, no 24, article id 241202Article in journal (Refereed) Published
    Abstract [en]

    The recent upswing in attention for the thermoelectric properties of organic semiconductors (OSCs) adds urgency to the need for a quantitative description of the range and energetics of hopping transport in organic semiconductors under relevant circumstances, i.e., around room temperature (RT). In particular, the degree to which hops beyond the nearest neighbor must be accounted for at RT is still largely unknown. Here, measurements of charge and energy transport in doped OSCs are combined with analytical modeling to reach the univocal conclusion that variable-range hopping is the proper description in a large class of disordered OSC at RT. To obtain quantitative agreement with experiment, one needs to account for the modification of the density of states by ionized dopants. These Coulomb interactions give rise to a deep tail of trap states that is independent of the materials initial energetic disorder. Insertion of this effect into a classical Mott-type variable-range hopping model allows one to give a quantitative description of temperature-dependent conductivity and thermopower measurements on a wide range of disordered OSCs. In particular, the model explains the commonly observed quasiuniversal power-law relation between the Seebeck coefficient and the conductivity.

    Place, publisher, year, edition, pages
    AMER PHYSICAL SOC, 2017
    National Category
    Condensed Matter Physics
    Identifiers
    urn:nbn:se:liu:diva-144143 (URN)10.1103/PhysRevB.96.241202 (DOI)000418616700001 ()
    Note

    Funding Agencies|Chinese Scholarship Council (CSC); Knut och Alice Wallenberg stiftelse

    Available from: 2018-01-10 Created: 2018-01-10 Last updated: 2018-08-29
    5. High Seebeck Coefficient and Power Factor in n-Type Organic Thermoelectrics
    Open this publication in new window or tab >>High Seebeck Coefficient and Power Factor in n-Type Organic Thermoelectrics
    2018 (English)In: ADVANCED ELECTRONIC MATERIALS, ISSN 2199-160X, Vol. 4, no 1, article id 1700501Article in journal (Refereed) Published
    Abstract [en]

    The n-type thermoelectric properties of [6,6]-phenyl-C-61-butyric acid methyl ester (PCBM) are investigated for different solution-based doping methods. A novel inverse-sequential doping method where the semiconductor (PCBM) is deposited on a previously cast dopant 4-(1,3-dimethyl-2,3-dihydro-1H-benzoimidazol-2-yl)-N,N-diphenylaniline film to achieve a very high power factor PF approximate to 35 mu W m(-1) K-2 with a conductivity sigma approximate to 40 S m(-1) is introduced. It is also shown that n-type organic semiconductors obey the -1/4 power law relation between Seebeck coefficient S and sigma that are previously found for p-type materials. An analytical model on basis of variable range hopping unifies these results. The power law for n-type materials is shifted toward higher conductivities by two orders of magnitude with respect to that of p-type, suggesting strongly that n-type organic semiconductors can eventually become superior to their p-type counterparts. Adding a small fraction lower lowest unoccupied molecular orbital material (core-cyanated naphthalene diimide) into PCBM leads to a higher S for inverse-sequential doping but not for bulk doping due to different morphologies.

    Place, publisher, year, edition, pages
    Wiley-VCH Verlagsgesellschaft, 2018
    Keywords
    n-type doping; organic thermoelectrics; power factor; Seebeck coefficient
    National Category
    Other Materials Engineering
    Identifiers
    urn:nbn:se:liu:diva-144566 (URN)10.1002/aelm.201700501 (DOI)000419670400026 ()
    Note

    Funding Agencies|Chinese Scholarship Council (CSC)

    Available from: 2018-01-29 Created: 2018-01-29 Last updated: 2018-05-14
    6. High thermoelectric power factor from multilayer solution-processed organic films
    Open this publication in new window or tab >>High thermoelectric power factor from multilayer solution-processed organic films
    2018 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 112, no 8, article id 083303Article in journal (Refereed) Published
    Abstract [en]

    We investigate the suitability of the "sequential doping" method of organic semiconductors for thermoelectric applications. The method consists of depositing a dopant (F4TCNQ) containing solution on a previously cast semiconductor (P3HT) thin film to achieve high conductivity, while preserving the morphology. For very thin films (similar to 25 nm), we achieve a high power factor around 8 mu W/mK(-2) with a conductivity over 500 S/m. For the increasing film thickness, conductivity and power factor show a decreasing trend, which we attribute to the inability to dope the deeper parts of the film. Since thick films are required to extract significant power from thermoelectric generators, we developed a simple additive technique that allows the deposition of an arbitrary number of layers without significant loss in conductivity or power factor that, for 5 subsequent layers, remain at similar to 300 S/m and similar to 5 mu W/mK(-2), respectively, whereas the power output increases almost one order of magnitude as compared to a single layer. The efficient doping in multilayers is further confirmed by an increased intensity of (bi)polaronic features in the UV-Vis spectra. Published by AIP Publishing.

    Place, publisher, year, edition, pages
    AMER INST PHYSICS, 2018
    National Category
    Materials Chemistry
    Identifiers
    urn:nbn:se:liu:diva-145764 (URN)10.1063/1.5016908 (DOI)000425977500021 ()
    Note

    Funding Agencies|China Scholarship Council (CSC); Knut och Alice Wallenbergs stiftelse (Project "Tail of the Sun")

    Available from: 2018-03-22 Created: 2018-03-22 Last updated: 2018-05-14
    7. Morphology Determines Conductivity and Seebeck Coefficient in Conjugated Polymer Blends
    Open this publication in new window or tab >>Morphology Determines Conductivity and Seebeck Coefficient in Conjugated Polymer Blends
    2018 (English)In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 10, no 11, p. 9638-9644Article in journal (Refereed) Published
    Abstract [en]

    The impact of nanoscale morphology on conductivity and Seebeck coefficient in p-type doped all-polymer blend systems is investigated. For a strongly phase separated system (P3HT:PTB7), we achieve a Seebeck coefficient that peaks at S similar to 1100 mu V/K with conductivity sigma similar to 3 x 10(-3) S/cm for 90% PTB7. In marked contrast, for well-mixed systems (P3HT:PTB7 with 5% diiodooctane (DIO), P3HT:PCPDTBT), we find an almost constant S similar to 140 mu V/K and sigma similar to 1 S/cm despite the energy levels being (virtually) identical in both cases. The results are interpreted in terms of a variable range hopping (VRH) model where a peak in S and a minimum in a arise when the percolation pathway contains both host and guest sites, in which the latter acts as energetic trap. For well-mixed blends of the investigated compositions, VRH enables percolation pathways that only involve isolated guest sites, whereas the large distance between guest clusters in phase separated blends enforces (energetically unfavorable) hops via the host. The experimentally observed trends are in good agreement with the results of atomistic kinetic Monte Carlo simulations accounting for the differences in nanoscale morphology.

    Place, publisher, year, edition, pages
    AMER CHEMICAL SOC, 2018
    Keywords
    Seebeck coefficient; morphology; charge transport; conjugated polymers; kinetic Monte Carlo simulations
    National Category
    Inorganic Chemistry
    Identifiers
    urn:nbn:se:liu:diva-147581 (URN)10.1021/acsami.8b00122 (DOI)000428356800052 ()29488380 (PubMedID)
    Note

    Funding Agencies|China Scholarship Council (CSC)

    Available from: 2018-04-26 Created: 2018-04-26 Last updated: 2018-05-18
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    Doping and Density of States Engineering for Organic Thermoelectrics
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  • 11500.
    Zuo, Guangzheng
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Complex Materials and Devices. Linköping University, Faculty of Science & Engineering.
    Abdalla, Hassan
    Linköping University, Department of Physics, Chemistry and Biology, Complex Materials and Devices. Linköping University, Faculty of Science & Engineering.
    Kemerink, Martijn
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Conjugated Polymer Blends for Organic Thermoelectrics2019In: ADVANCED ELECTRONIC MATERIALS, ISSN 2199-160X, Vol. 5, no 11, article id 1800821Article in journal (Refereed)
    Abstract [en]

    A major attraction of organic conjugated semiconductors is that materials with new, emergent functionality can be designed and made by simple blending, as is extensively used in, e.g., bulk heterojunction organic solar cells. Herein doped blends based on organic semiconductors (OSCs) for thermoelectric applications are critically reviewed. Several experimental strategies to improve thermoelectric performance, measured in terms of power factor (PF) or figure-of-merit ZT, have been demonstrated in recent literature. Specifically, density-of-states design in blends of two OSCs can be used to obtain electronic Seebeck coefficients up to approximate to 2000 mu V K-1. Alternatively, blending with (high-dielectric constant) insulating polymers can improve doping efficiency and thereby conductivity, as well as induce more favorable morphologies that improve conductivity while hardly affecting thermopower. In the PEDOT:polystyrene-sulfonate (PEDOT:PSS) blend system, processing schemes to either improve conductivity via morphology or via (partial) removal of the electronically isolating PSS, or both, have been demonstrated. Although a range of experiments have at least quasi-quantitatively been explained by analytical or numerical models, a comprehensive model for organic thermoelectrics is lacking so far.

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