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  • 1.
    Chalangar, Ebrahim
    et al.
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS), Tillämpad matematik och fysik (MPE-lab). Linköping University, Norrköping, Sweden.
    Machhadani, Houssaine
    Linköping University, Linköping, Sweden.
    Lim, Seung-Hyuk
    Linköping University, Linköping, Sweden.
    Karlsson, K. Fredrik
    Linköping University, Linköping, Sweden.
    Nur, Omer
    Linköping University, Norrköping, Sweden.
    Willander, Magnus
    Linköping University, Norrköping, Sweden.
    Pettersson, Håkan
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS), Tillämpad matematik och fysik (MPE-lab). Linköping University, Norrköping, Sweden & Lund University, Lund, Sweden.
    Influence of morphology on electrical and optical properties of graphene/Al-doped ZnO-nanorod composites2018Inngår i: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 29, nr 41, artikkel-id 415201Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The development of future 3D-printed electronics relies on the access to highly conductive inexpensive materials that are printable at low temperatures (<100 C). The implementation of available materials for these applications are, however, still limited by issues related to cost and printing quality. Here, we report on the simple hydrothermal growth of novel nanocomposites that are well suited for conductive printing applications. The nanocomposites comprise highly Al-doped ZnO nanorods grown on graphene nanoplatelets (GNPs). The ZnO nanorods play the two major roles of (i) preventing GNPs from agglomerating and (ii) promoting electrical conduction paths between the graphene platelets. The effect of two different ZnO-nanorod morphologies with varying Al-doping concentration on the nanocomposite conductivity and the graphenedispersity are investigated. Time-dependent absorption, photoluminescence and photoconductivity measurements show that growth in high pH solutions promotes a better graphene dispersity, higher doping levels and enhanced bonding between the graphene and the ZnO nanorods. Growth in low pH solutions yields samples characterized by a higher conductivity and a reduced number of surface defects. These samples also exhibit a large persistent photoconductivity attributed to an effective charge separation and transfer from the nanorods to the graphene platelets. Our findings can be used to tailor the conductivity of novel printable composites, or for fabrication of large volumes of inexpensive porous conjugated graphene-semiconductor composites. © 2018 IOP Publishing Ltd.

  • 2.
    Corrêa Jr, Gregório B.
    et al.
    Instituto Federal de Educação, Ciência e Tecnologia do Pará, Abaetetuba, PA, Brazil & Programa de Pós-Graduação em Física, Universidade Federal do Pará, Belém, PA, Brazil & .
    Kumar, Sandeep
    Department of Physics, Central University of Rajasthan, Ajmer, India.
    Paschoal Jr, Waldomiro
    Programa de Pós-Graduação em Física, Universidade Federal do Pará, Belém, PA, Brazil.
    Devi, Chandni
    Department of Physics, Central University of Rajasthan, Ajmer, India.
    Jacobsson, Daniel
    Department of Chemistry, Lund University, Lund, Sweden.
    Johannes, Andreas
    Institut für Festkörperphysik, Friedrich-Schiller-Universität Jena, Jena, Germany.
    Ronning, Carsten
    Institut für Festkörperphysik, Friedrich-Schiller-Universität Jena, Jena, Germany.
    Pettersson, Håkan
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS). Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Paraguassu, Waldeci
    Programa de Pós-Graduação em Física, Universidade Federal do Pará, Belém, PA, Brazil.
    Raman characterization of single-crystalline Ga0.96Mn0.04As:Zn nanowires realized by ion-implantation2019Inngår i: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 30, nr 33, artikkel-id 335202Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Recent progress in the realization of magnetic GaAs nanowires (NWs) doped with Mn has attracted a lot of attention due to their potential application in spintronics. In this work, we present a detailed Raman investigation of the structural properties of Zn doped GaAs (GaAs:Zn) and Mn-implanted GaAs:Zn (Ga0.96Mn0.04As:Zn) NWs. A significant broadening and redshift of the optical TO and LO phonon modes are observed for these NWs compared to as-grown undoped wires, which is attributed to strain induced by the Zn/Mn doping and to the presence of implantation-related defects. Moreover, the LO phonon modes are strongly damped, which is interpreted in terms of a strong LO phonon-plasmon coupling, induced by the free hole concentration. Moreover, we report on two new interesting Raman phonon modes (191 and 252 cm −1) observed in Mn ion-implanted NWs, which we attribute to Eg (TO) and A1g (LO) vibrational modes in a sheet layer of crystalline arsenic present on the surface of the NWs. This conclusion is supported by fitting the observed Raman shifts for the SO phonon modes to a theoretical dispersion function for a GaAs NW capped with a dielectric shell. © 2019 IOP Publishing Ltd.

  • 3.
    Hussain, Laiq
    et al.
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS). Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Karimi, Mohammad
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS). Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Berg, Alexander
    Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Jain, Vishal
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS). Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Borgström, Magnus T.
    Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Gustafsson, Anders
    Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Samuelson, Lars
    Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Pettersson, Håkan
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS). Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Defect-induced infrared electroluminescence from radial GaInP/AlGaInP quantum well nanowire array light- emitting diodes2017Inngår i: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 28, nr 48, artikkel-id 485205Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Radial GaInP/AlGaInP nanowire array light-emitting diodes (LEDs) are promising candidates for novel high-efficiency solid state lighting due to their potentially large strain-free active emission volumes compared to planar LEDs. Moreover, by proper tuning of the diameter of the nanowires, the fraction of emitted light extracted can be significantly enhanced compared to that of planar LEDs. Reports so far on radial growth of nanowire LED structures, however, still point to significant challenges related to obtaining defect-free radial heterostructures. In this work, we present evidence of optically active growth-induced defects in a fairly broad energy range in vertically processed radial GaInP/AlGaInP quantum well nanowire array LEDs using a variety of complementary experimental techniques. In particular, we demonstrate strong infrared electroluminescence in a spectral range centred around 1 eV (1.2 μm) in addition to the expected red light emission from the quantum well. Spatially resolved cathodoluminescence studies reveal a patchy red light emission with clear spectral features along the NWs, most likely induced by variations in QW thickness, composition and barriers. Dark areas are attributed to infrared emission generated by competing defect-assisted radiative transitions, or to trapping mechanisms involving non-radiative recombination processes. Possible origins of the defects are discussed. © 2017 IOP Publishing Ltd

  • 4.
    Jain, Vishal
    et al.
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS), Tillämpad matematik och fysik (MPE-lab). Solid State Physics and Nano, Lund University, Lund, Sweden.
    Heurlin, Magnus
    Solid State Physics and Nano, Lund University, Lund, Sweden.
    Karimi, Mohammad
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS), Tillämpad matematik och fysik (MPE-lab). Solid State Physics and Nano, Lund University, Lund, Sweden.
    Hussain, Laiq
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS), Tillämpad matematik och fysik (MPE-lab). Solid State Physics and Nano, Lund University, Lund, Sweden.
    Aghaeipour, Mahtab
    Solid State Physics and Nano, Lund University, Lund, Sweden.
    Nowzari, Ali
    Solid State Physics and Nano, Lund University, Lund, Sweden.
    Berg, Alexander
    Solid State Physics and Nano, Lund University, Lund, Sweden.
    Nylund, Gustav
    Solid State Physics and Nano, Lund University, Lund, Sweden.
    Capasso, Federico
    Harvard University, Cambridge, United States of America.
    Samuelson, Lars
    Solid State Physics and Nano, Lund University, Lund, Sweden.
    Borgström, Magnus T.
    Solid State Physics and Nano, Lund University, Lund, Sweden.
    Pettersson, Håkan
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS), Tillämpad matematik och fysik (MPE-lab). Solid State Physics and Nano, Lund University, Lund, Sweden.
    Bias-dependent spectral tuning in InP nanowire-based photodetectors2017Inngår i: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 28, nr 11, artikkel-id 114006Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Nanowire array ensembles contacted in a vertical geometry are extensively studied and considered strong candidates for next generations of industrial scale optoelectronics. Key challenges in this development deal with optimization of the doping profile of the nanowires and the interface between nanowires and transparent top contact. Here we report on photodetection characteristics associated with doping profile variations in InP nanowire array photodetectors. Bias-dependent tuning of the spectral shape of the responsivity is observed which is attributed to a Schottky-like contact at the nanowire-ITO interface. Angular dependent responsivity measurements, compared with simulated absorption spectra, support this conclusion. Furthermore, electrical simulations unravel the role of possible self-gating effects in the nanowires induced by the ITO/SiOx wrap-gate geometry. Finally, we discuss possible reasons for the observed low saturation current at large forward biases.  

  • 5.
    Liu, Ruisheng
    et al.
    Högskolan i Halmstad, Sektionen för Informationsvetenskap, Data– och Elektroteknik (IDE), Halmstad Embedded and Intelligent Systems Research (EIS), Tillämpad matematik och fysik (CAMP).
    Suyatin, D.
    Lund University.
    Pettersson, Håkan
    Högskolan i Halmstad, Sektionen för Informationsvetenskap, Data– och Elektroteknik (IDE), Halmstad Embedded and Intelligent Systems Research (EIS), Tillämpad matematik och fysik (CAMP).
    Samuelson, L.
    Lund University.
    Assembling ferromagnetic single-electron transistors by atomic force microscopy2007Inngår i: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 18, nr 5, s. 055302-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We demonstrate the assembly of nanoscale ferromagnetic single-electron transistors using atomic force microscopy for imaging as well as for nanoscale manipulation. A single 30 nm Au disc, forming the central island of the transistor, is manipulated with angstrom precision into the gap between a plasma-oxidized Ni source and drain electrodes. The tunnel resistances can be tuned in real time during the device fabrication by repositioning the Au disc. Transport measurements reveal long-term stable single-electron transistor characteristics at 4.2 K. The well-controlled devices with very small central islands facilitate future in-depth studies of the interplay between Coulomb blockade, spin-dependent tunnelling and spin accumulation in ferromagnetic single-electron transistors at elevated temperatures.

  • 6.
    Pettersson, Håkan
    et al.
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS), Tillämpad matematik och fysik (MPE-lab).
    Zubritskaya, Irina
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS), Tillämpad matematik och fysik (MPE-lab).
    Nghia, Ngo Tuan
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS), Tillämpad matematik och fysik (MPE-lab).
    Wallentin, Jesper
    Solid State Physics and the Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Borgström, Magnus T.
    Solid State Physics and the Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Storm, Kristian
    Solid State Physics and the Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Landin, Lars
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS), Tillämpad matematik och fysik (MPE-lab).
    Wickert, Peter
    Sol Voltaics AB, Ideon Science Park, Lund, Sweden.
    Capasso, Federico
    School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, USA.
    Samuelson, Lars
    Solid State Physics and the Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Electrical and optical properties of InP nanowire ensemble p(+)-i-n(+) photodetectors2012Inngår i: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 23, nr 13, artikkel-id 135201Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report on a comprehensive study of electrical and optical properties of efficient near-infrared p(+)-i-n(+) photodetectors based on large ensembles of self-assembled, vertically aligned i-n(+) InP nanowires monolithically grown on a common p(+) InP substrate without any buffer layer. The nanowires have a polytype modulated crystal structure of wurtzite and zinc blende. The electrical data display excellent rectifying behavior with an ideality factor of about 2.5 at 300 K. The ideality factor scales with 1/T, which possibly reflects deviations from classical transport models due to the mixed crystal phase of the nanowires. The observed dark leakage current is of the order of merely similar to 100 fA/nanowire at 1 V reverse bias. The detectors display a linear increase of the photocurrent with reverse bias up to about 10 pA/nanowire at 5 V. From spectrally resolved measurements, we conclude that the photocurrent is primarily generated by funneling photogenerated carriers from the substrate into the NWs. Contributions from direct excitation of the NWs become increasingly important at low temperatures. The photocurrent decreases with temperature with an activation energy of about 50 meV, which we discuss in terms of a temperature-dependent diffusion length in the substrate and perturbed transport through the mixed-phase nanowires. © 2012 IOP Publishing Ltd.

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