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  • 1.
    Borschel, Christian
    et al.
    Institute for Solid State Physics, Jena University, Max-Wien-Platz 1, 07743 Jena, Germany.
    Messing, Maria
    Avd. f. Fasta tillståndets fysik, Lunds Universitet.
    Borgström, Magnus T.
    Avd. f. Fasta tillståndets fysik, Lunds Universitet.
    Paschoal, Waldomiro
    Avd. f. Fasta tillståndets fysik, Lunds Universitet / Tillämpad matematik och fysik (MPE-lab), MPE-lab.
    Wallentin, Jesper
    Avd. f. Fasta tillståndets fysik, Lunds Universitet.
    Kumar, Sandeep
    Avd. f. Fasta tillståndets fysik, Lunds Universitet.
    Mergenthaler, Kilian
    Avd. f. Fasta tillståndets fysik, Lunds Universitet.
    Deppert, Knut
    Avd. f. Fasta tillståndets fysik, Lunds Universitet.
    Canali, C. M.
    Högskolan i Kalmar.
    Pettersson, Håkan
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), MPE-lab.
    Samuelson, Lars
    Avd. f. Fasta tillståndets fysik, Lunds Universitet.
    Ronning, Carsten
    Institute for Solid State Physics, Jena University, Max-Wien-Platz 1, 07743 Jena, Germany.
    A New Route toward Semiconductor Nanospintronics: Highly Mn-Doped GaAs Nanowires Realized by Ion-Implantation under Dynamic Annealing Conditions2011In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 11, no 9, p. 3935-3940Article in journal (Refereed)
    Abstract [en]

    We report on highly Mn-doped GaAs nanowires (NWs) of high crystalline quality fabricated by ion beam implantation, a technique that allows doping concentrations beyond the equilibrium solubility limit. We studied two approaches for the preparation of Mn-doped GaAs NWs: First, ion implantation at room temperature with subsequent annealing resulted in polycrystalline NWs and phase segregation of MnAs and GaAs. The second approach was ion implantation at elevated temperatures. In this case, the single-crystallinity of the GaAs NWs was maintained, and crystalline, highly Mn-doped GaAs NWs were obtained. The electrical resistance of such NWs dropped with increasing temperature (activation energy about 70 meV). Corresponding magnetoresistance measurements showed a decrease at low temperatures, indicating paramagnetism. Our findings suggest possibilities for future applications where dense arrays of GaMnAs nanowires may be used as a new kind of magnetic material system.

  • 2.
    Borschel, Christian
    et al.
    Institute for Solid State Physics, University of Jena, Jena, Germany.
    Messing, Maria
    Lund University, Lund, Sweden.
    Mergenthaler, Kilian
    Lund University, Lund, Sweden.
    Borgström, Magnus T.
    Lund University, Lund, Sweden.
    Paschoal, Waldomiro
    Lund University, Lund, Sweden.
    Wallentin, Jesper
    Lund University, Lund, Sweden.
    Kumar, Sandeep
    Lund University, Lund, Sweden.
    Deppert, Knut
    Lund University, Lund, Sweden.
    Canali, Carlo
    Linnaeus University, Kalmar, Sweden.
    Pettersson, Håkan
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), MPE-lab.
    Samuelson, Lars
    Lund University, Lund, Sweden.
    Ronning, Carsten
    Institute for Solid State Physics, University of Jena, Jena, Germany.
    A New Route towards Semiconductor Nanospintronics: Highly Mn-Doped GaAs Nanowires Realized by Ion-Implantation under Dynamic Annealing Conditions2011Conference paper (Refereed)
  • 3.
    Johannes, A.
    et al.
    Institute for Solid State Physics, Friedrich-Schiller-University Jena, Jena, Germany.
    Noack, S.
    Institute for Solid State Physics, Friedrich-Schiller-University Jena, Jena, Germany.
    Paschoal Jr., Waldomiro
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS). Solid State Physics/The Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Kumar, Sandeep
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS). Solid State Physics/The Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Jacobsson, D.
    Solid State Physics/The Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Pettersson, Håkan
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS). Solid State Physics/The Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Samuelson, L.
    Solid State Physics/The Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Dick, K. A.
    Lund University, Lund, Sweden.
    Martinez-Criado, G.
    European Synchrotron Radiation Facility, Grenoble, France.
    Burghammer, M.
    European Synchrotron Radiation Facility, Grenoble, France.
    Ronning, C.
    Institute for Solid State Physics, Friedrich-Schiller-University Jena, Jena, Germany.
    Corrigendum: Enhanced sputtering and incorporation of Mn in implanted GaAs and ZnO nanowires (2014 J. Phys. D: Appl. Phys. 47 394003)2015In: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 48, no 7, article id 079501Article in journal (Refereed)
  • 4.
    Johannes, Andreas
    et al.
    Institute for Solid State Physics, Friedrich-Schiller-University Jena, Jena, Germany.
    Noack, Stefan
    Institute for Solid State Physics, Friedrich-Schiller-University Jena, Jena, Germany.
    Paschoal Jr, Waldomiro
    Halmstad University, School of Information Technology. Solid State Physics/The Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Kumar, Sandeep
    Halmstad University, School of Information Technology. Solid State Physics/The Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Jacobsson, Daniel
    Solid State Physics/The Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Pettersson, Håkan
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), MPE-lab. Solid State Physics/The Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Samuelson, Lars
    Solid State Physics/The Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Dick, Kimberly A.
    Centre for Analysis and Synthesis, Lund University, Lund, Sweden.
    Martinez-Criado, G.
    European Synchrotron Radiation Facility, Grenoble, France.
    Burghammer, M.
    European Synchrotron Radiation Facility, Grenoble, France.
    Ronning, Carsten
    Institute for Solid State Physics, Friedrich-Schiller-University Jena, Jena, Germany.
    Enhanced sputtering and incorporation of Mn in implanted GaAs and ZnO nanowires2014In: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 47, no 39, article id 394003Article in journal (Refereed)
    Abstract [en]

    We simulated and experimentally investigated the sputter yield of ZnO and GaAs nanowires, which were implanted with energetic Mn ions at room temperature. The resulting thinning of the nanowires and the dopant concentration with increasing Mn ion fluency were measured by accurate scanning electron microscopy (SEM) and nano-x-Ray Fluorescence (nanoXRF) quantification, respectively. We observed a clearly enhanced sputter yield for the irradiated nanowires compared to bulk, which is also corroborated by iradina simulations. These show a maximum if the ion range matches the nanowire diameter. As a consequence of the erosion thinning of the nanowire, the incorporation of the Mn dopants is also enhanced and increases non-linearly with increasing ion fluency. © 2014 IOP Publishing Ltd.

  • 5.
    Kumar, Sandeep
    et al.
    Solid State Physics/The Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Paschoal, Waldomiro
    Solid State Physics/The Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Johannes, Andreas
    Institute for Solid State Physics, Jena University, Jena, Germany.
    Jacobsson, Daniel
    Solid State Physics/The Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Borschel, Christian
    Institute for Solid State Physics, Jena University, Jena, Germany.
    Pertsova, Anna
    Linneaus University, Kalmar, Sweden.
    Wang, Chih-Han
    Institute of Physics, Academia Sinica, Taipei, Taiwan.
    Wu, Maw-Kuen
    Institute of Physics, Academia Sinica, Taipei, Taiwan.
    Canali, C. M.
    Linneaus University, Kalmar, Sweden.
    Ronning, Carsten
    Institute for Solid State Physics, Jena University, Jena, Germany.
    Samuelson, Lars
    Solid State Physics/The Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Pettersson, Håkan
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS). Solid State Physics/The Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Magnetic Polarons and Large Negative Magnetoresistance in GaAs Nanowires implanted with Mn Ions2013In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 13, no 11, p. 5079-5084Article in journal (Refereed)
    Abstract [en]

    We report on low-temperature magnetotransport and SQUID measurements on heavily doped Mn-implanted GaAs nanowires. SQUID data recorded at low magnetic fields exhibit clear signs of the onset of a spin-glass phase with a transition temperature of about 16 K. Magnetotransport experiments reveal a corresponding peak in resistance at 16 K and a large negative magnetoresistance, reaching 40% at 1.6 K and 8 T. The negative magnetoresistance decreases at elevated temperatures and vanishes at about 100 K. We interpret our transport data in terms of spin-dependent hopping in a complex magnetic nanowire landscape of magnetic polarons, separated by intermediate regions of Mn impurity spins, forming a paramagnetic/spin-glass phase. Copyright © 2013 American Chemical Society

  • 6.
    Paschoal Jr., Waldomiro
    et al.
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), Applied Mathematics and Physics (CAMP). Solid State Physics/The Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Kumar, Sandeep
    Solid State Physics/The Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Borschel, Christian
    Institute for Solid State Physics, Jena University, Jena, Germany.
    Borgström, Magnus
    Solid State Physics/The Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Ronning, Carsten
    Institute for Solid State Physics, Jena University, Jena, Germany.
    Canali, Carlo
    Division of Physics, School of Computer Science, Physics and Mathematics, Linneaus University, Kalmar, Sweden.
    Samuelson, Lars
    Solid State Physics/The Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Pettersson, Håkan
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), Applied Mathematics and Physics (CAMP). Solid State Physics/The Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Electron transport in Mn+ implanted GaAs nanowires2012Conference paper (Refereed)
    Abstract [en]

    Mn-doped GaAs semiconductors have generated great interest in current research regarding the evolution from a paramagnetic insulator to a ferromagnetic metal governed by a carrier mediated exchange interaction. The interplay between the charge carriers in a semiconductor and the electron spin of incorporated ferromagnetic metals can be utilized for novel spin-sensitive spintronic devices. We have fabricated highly Mn-doped, single-crystalline GaAs nanowires (NWs) by ion implantation at elevated temperatures to facilitate in-situ dynamic annealing. To exploit these nanowires in spintronic applications, a detailed understanding of fundamental charge transport mechanisms is however necessary. It is generally expected that new features, different from any bulk counterparts, will emerge in systems with reduced dimensionality e.g. quasi-1D NWs. Here we report on a detailed study of different charge transport mechanisms and localization-related effects in single Mn-doped GaAs NWs in the temperature range from 300K to 1.6K, and with magnetic fields ranging from 0T to 8T. In general, the resistance of the nanowires increases strongly from a few M* at 300K to several G* at 1.6 K. More specially, the temperature dependence displays several different interesting regimes described by distinctly different models. Furthermore, the current-voltage (I-V) characteristics becomes strongly non-linear as the temperature decreases and shows apparent power-law behavior at low temperatures. In particular, we interpret our transport data in the temperature range from 80K to 275K in terms of a variable range hopping process influenced by Mn-induced disorder in the NWs. Below 50K the magnetotransport data reveals a large negative magnetoresistance (MR) under both paralleland perpendicular magnetic fields. We are presently developing models to explain this large MR signal, including low-temperature transport mechanisms and possible magnetic interaction between Mn ions.

  • 7.
    Paschoal Jr., Waldomiro
    et al.
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), Halmstad Embedded and Intelligent Systems Research (EIS).
    Kumar, Sandeep
    Solid State Physics/The Nanometer Structure Consortium, Lund University, Box 118, SE-221 00 Lund, Sweden.
    Borschel, Christian
    Institute for Solid State Physics, Jena University, Max-Wien-Platz 1, 07743 Jena, Germany.
    Wu, Phillip
    Solid State Physics/The Nanometer Structure Consortium, Lund University, Box 118, SE-221 00 Lund, Sweden.
    Canali, Carlo M.
    Division of Physics, School of Computer Science, Physics and Mathematics, Linneaus University, 39233 Kalmar, Sweden.
    Ronning, Carsten
    Institute for Solid State Physics, Jena University, Max-Wien-Platz 1, 07743 Jena, Germany.
    Samuelson, Lars
    Solid State Physics/The Nanometer Structure Consortium, Lund University, Box 118, SE-221 00 Lund, Sweden.
    Pettersson, Håkan
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), Halmstad Embedded and Intelligent Systems Research (EIS).
    Hopping Conduction in Mn Ion-Implanted GaAs Nanowires2012In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 12, no 9, p. 4838-4842Article in journal (Refereed)
    Abstract [en]

    We report on temperature-dependent charge transport in heavily doped Mn+ implanted GaAs nanowires.The results clearly demonstrate that the transport is governedby temperature-dependent hopping processes, with a crossoverbetween nearest neighbor hopping and Mott variable rangehopping at about 180 K. From detailed analysis, we haveextracted characteristic hopping energies and correspondinghopping lengths. At low temperatures, a strongly nonlinearconductivity is observed which reflects a modified hoppingprocess driven by the high electric field at large bias.

  • 8.
    Paschoal Jr., Waldomiro
    et al.
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), MPE-lab. Solid State Physics/The Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Kumar, Sandeep
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), MPE-lab. Solid State Physics/The Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Jacobsson, Daniel
    Solid State Physics/The Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Johannes, Andreas
    Institute for Solid State Physics, Jena University, Jena, Germany.
    Jain, Vishal
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), MPE-lab. Solid State Physics/The Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Canali, Carlo M.
    Department of Physics and Electrical Engineering, Linneaus University, Kalmar, Sweden.
    Pertsova, Anna
    Department of Physics and Electrical Engineering, Linneaus University, Kalmar, Sweden.
    Ronning, Carsten
    Institute for Solid State Physics, Jena University, Jena, Germany.
    Dick, Kimberly A.
    Solid State Physics/The Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Samuelson, Lars
    Solid State Physics/The Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Pettersson, Håkan
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), MPE-lab.
    Magnetoresistance in Mn ion-implanted GaAs:Zn nanowires2014In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 104, no 15, article id 153112Article in journal (Refereed)
    Abstract [en]

    We have investigated the magnetoresistance (MR) in a series of Zn doped (p-type) GaAs nanowires implanted with different Mn concentrations. The nanowires with the lowest Mn concentration (~0.0001%) exhibit a low resistance of a few kΩ at 300K and a 4% positive MR at 1.6K, which can be well described by invoking a spin-split subband model. In contrast, nanowires with the highest Mn concentration (4%) display a large resistance of several MΩ at 300K and a large negative MR of 85% at 1.6K. The large negative MR is interpreted in terms of spin-dependent hopping in a complex magnetic nanowire landscape of magnetic polarons, separated by intermediate regions of Mn impurity spins. Sweeping the magnetic field back and forth for the 4% sample reveals a hysteresis that indicates the presence of a weak ferromagnetic phase. We propose co-doping with Zn to be a promising way to reach the goal of realizing ferromagnetic Ga1-xMnxAs nanowires for future nanospintronics. © 2014 AIP Publishing LLC.

  • 9.
    Wu, Phillip M.
    et al.
    Division of Solid State Physics and the Nanometer Structure Consortium (NmC at LU), Lund University, P.O. Box 118, 221 00 Lund, Sweden.
    Paschoal Jr., Waldomiro
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS).
    Kumar, Sandeep
    Division of Solid State Physics and the Nanometer Structure Consortium (NmC at LU), Lund University, P.O. Box 118, 221 00 Lund, Sweden.
    Borschel, Christian
    Institute for Solid State Physics, Jena University, Max-Wien-Platz 1, 07743 Jena, Germany.
    Ronning, Carsten
    Institute for Solid State Physics, Jena University, Max-Wien-Platz 1, 07743 Jena, Germany.
    Canali, Carlo M.
    Division of Physics, School of Computer Science, Linnæus University, 39233 Kalmar, Sweden.
    Samuelson, Lars
    Division of Solid State Physics and the Nanometer Structure Consortium (NmC at LU), Lund University, P.O. Box 118, 221 00 Lund, Sweden.
    Pettersson, Håkan
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS).
    Linke, Heiner
    Division of Solid State Physics and the Nanometer Structure Consortium (NmC at LU), Lund University, P.O. Box 118, 221 00 Lund, Sweden.
    Thermoelectric Characterization of Electronic Properties of GaMnAs Nanowires2012In: Journal of Nanotechnology, ISSN 1687-9503, E-ISSN 1687-9511, Vol. 2012, article id 480813Article in journal (Refereed)
    Abstract [en]

    Nanowires with magnetic doping centers are an exciting candidate for the study of spin physics and proof-of-principle spintronics devices. The required heavy doping can be expected to have a significant impact on the nanowires' electron transport properties. Here, we use thermopower and conductance measurements for transport characterization of Ga 0.95Mn 0.05As nanowires over a broad temperature range. We determine the carrier type (holes) and concentration and find a sharp increase of the thermopower below temperatures of 120 K that can be qualitatively described by a hopping conduction model. However, the unusually large thermopower suggests that additional mechanisms must be considered as well. © 2012 Phillip M. Wu et al.

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