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  • 51.
    Paschoal Jr., Waldomiro
    et al.
    Högskolan i Halmstad, Sektionen för Informationsvetenskap, Data– och Elektroteknik (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
    Högskolan i Halmstad, Sektionen för Informationsvetenskap, Data– och Elektroteknik (IDE), Halmstad Embedded and Intelligent Systems Research (EIS).
    Hopping Conduction in Mn Ion-Implanted GaAs Nanowires2012Ingår i: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 12, nr 9, s. 4838-4842Artikel i tidskrift (Refereegranskat)
    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.

  • 52.
    Persson, A. I. H.
    et al.
    Department of Physics, Lund University, Lund, Sweden.
    Enquist, H.
    MAX IV Laboratory, Lund University, Lund, Sweden.
    Jurgilaitis, A.
    MAX IV Laboratory, Lund University, Lund, Sweden.
    Andreasson, Björn Pererik
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS). Department of Physics, Lund University, Lund, Sweden.
    Larsson, J.
    Department of Physics & MAX IV Laboratory, Lund University, Lund, Sweden.
    Real-time observation of coherent acoustic phonons generated by an acoustically mismatched optoacoustic transducer using x-ray diffraction2015Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 118, nr 18, artikel-id 185308Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The spectrum of laser-generated acoustic phonons in indium antimonide coated with a thin nickel film has been studied using time-resolved x-ray diffraction. Strain pulses that can be considered to be built up from coherent phonons were generated in the nickel film by absorption of short laser pulses. Acoustic reflections at the Ni-InSb interface leads to interference that strongly modifies the resulting phonon spectrum. The study was performed with high momentum transfer resolution together with high time resolution. This was achieved by using a third-generation synchrotron radiation source that provided a high-brightness beam and an ultrafast x-ray streak camera to obtain a temporal resolution of 10 ps. We also carried out simulations, using commercial finite element software packages and on-line dynamic diffraction tools. Using these tools, it is possible to calculate the time-resolved x-ray reflectivity from these complicated strain shapes. The acoustic pulses have a peak strain amplitude close to 1%, and we investigated the possibility to use this device as an x-ray switch. At a bright source optimized for hard x-ray generation, the low reflectivity may be an acceptable trade-off to obtain a pulse duration that is more than an order of magnitude shorter. © 2015 Author(s).

  • 53.
    Pettersson, Håkan
    Högskolan i Halmstad, Sektionen för Informationsvetenskap, Data– och Elektroteknik (IDE), Halmstad Embedded and Intelligent Systems Research (EIS), Tillämpad matematik och fysik (MPE-lab). Nanometer Structure Consortium, Lund University.
    Nanoscale devices for future opto-and magnetoelectronics2008Konferensbidrag (Refereegranskat)
  • 54.
    Pettersson, Håkan
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS), Tillämpad matematik och fysik (MPE-lab).
    Nanowire Infrared Photodetectors2016Konferensbidrag (Refereegranskat)
    Abstract [en]

    Over the last two decades there has been a dramatic increase in research activities related to semiconductor nanowires (NWs) due to their exciting prospects for implementation of novel high-performance electronics and photonics compatible with main-stream silicon technology.  In this talk, I will give an overview of our research efforts on infrared photodetectors based on InP/InAsP semiconductor NWs. I will discuss growth, processing and characterization of both single NW devices and large square millimeter array devices comprising millions of NWs connected in parallel. The electrical data generally display excellent rectifying behavior with small leakage currents. From optical measurements, combined with modeling, we conclude that the photocurrent generation depends strongly on the geometry and doping of the NW devices. Properly designed, the absorption of IR radiation in array devices can be significantly enhanced by nanophotonic resonances induced by the geometry and spatially matched to the position of the embedded p-n junctions in the NWs yielding high-efficiency photovoltaics. We have also carried out in-depth studies of InP NW arrays with multiple enclosed axial InAsP quantum wells for broadband and thermal imaging applications. Finally, I will discuss our recent research efforts targeting single InP/InAsP NW avalanche photodetectors with separate absorption and multiplication regions. The presented photodetectors can potentially be grown on cheap silicon substrates due to the small footprint of the NWs. Successfully developed, novel low-cost and high-performance detector families for optical communication, thermal imaging and solar cell applications can be realized.

  • 55.
    Pettersson, Håkan
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS), Tillämpad matematik och fysik (MPE-lab).
    Nanowire-based Infrared Photodetectors2015Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this talk, I will discuss electrical and optical properties of infrared photodetectors/solar cells based on  square millimeter ensembles (> 1 million) of vertically processed InP/InAsP semiconductor nanowires grown on InP substrates.

    To investigate current generation processes in InP p+-i-n photodetectors/solar cells, we fabricated a sample series where the p+-segment length was varied, as well as optimized solar cells with 9.3 % efficiency with similar design. The electrical data generally display excellent rectifying behavior with small leakage currents. From spectrally resolved photocurrent measurements, we conclude that the photocurrent generation process depends strongly on the p+-segment length. Without p+-segment, photogenerated carriers funneled from the substrate into the NWs contribute significantly to the photocurrent. Adding a p+-segment decouples the substrate and shifts the depletion region, and collection of photogenerated carriers, to the nanowires, in agreement with sophisticated theoretical modeling. In optimized solar cells, clear spectral signatures of interband transitions in the ZB and WZ InP layers of the mixed-phase i-segments are observed. Complementary measurements of the dependence of the photocurrent on angle of incidence and polarization, as well as electroluminescence, support our interpretations.

    I will also discuss large area photoconductors based on n-i-n InP nanowires with axial InAsP quantum wells embedded in the i-region. Spectrally resolved photocurrent measurements and photoluminescence measurements reveal clear interband transitions both in the InP segments and InAsP quantum wells. By increasing the number of incorporated quantum wells, one important goal is to enhance the contribution from intersubband transitions in the quantum wells thereby facilitating detectors/focal plane arrays with a broad detection window from near-infrared to long-wavelength infrared regions.

    Finally, I will briefly mention efforts targeting large area p+-n-n-  InP/InAsP avalanche nanowire photodiodes with low electric field in the low-bandgap InAsP segment and high electric field in the InP multiplication region. Besides clear interband photocurrent signals from the InP and InAsP regions, a strong bias-dependent blueshifted photocurrent peak appears at forward bias offering an interesting novel tunability of the spectral window.

    The presented nanowire-based photodetectors can potentially be grown on silicon substrates due to the small footprint of the nanowires. Successfully developed, novel detector families of low-cost, high performance broadband detectors for optical communication, thermal imaging and solar cell applications can thus be realized.

  • 56.
    Pettersson, Håkan
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS), Tillämpad matematik och fysik (MPE-lab).
    Nanowire-based infrared photodetectors2014Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this talk, I will discuss electrical and optical properties of infrared photodetectors/solar cells based on square millimeter ensembles (> 1 million) of vertically processed InP/InAsP semiconductor nanowires grown on InP substrates.

       To investigate current generation processes in InP p+-i-n photodetectors/solar cells, we fabricated a sample series where the p+-segment length was varied, as well as optimized solar cells with 9.3 % efficiency with similar design. The electrical data generally display excellent rectifying behavior with small leakage currents. From spectrally resolved photocurrent measurements, we conclude that the photocurrent generation process depends strongly on the p+-segment length. Without p+-segment, photogenerated carriers funneled from the substrate into the NWs contribute significantly to the photocurrent. Adding a p+-segment decouples the substrate and shifts the depletion region, and collection of photogenerated carriers, to the nanowires, in agreement with sophisticated theoretical modeling. In optimized solar cells, clear spectral signatures of interband transitions in the ZB and WZ InP layers of the mixed-phase i-segments are observed. Complementary measurements of the dependence of the photocurrent on angle of incidence and polarization, as well as electroluminescence, support our interpretations.

        I will also discuss large area photoconductors based on n+-i- n+ InP NWs with embedded InAsP QWs grown in axial geometry on InP substrates. Spectrally resolved photocurrent measurements and photoluminescence measurements reveal clear interband transitions both in the InP segments and InAsP quantum wells. By increasing the number of incorporated quantum wells in the nanowires, the contribution from intersubband transitions in the quantum wells can be enhanced thereby facilitating detectors/focal plane arrays with a broad detection window from near-infrared to long-wavelength infrared regions.

    Finally, I will briefly mention efforts targeting large area p+-n-n-  InP/InAsP avalanche nanowire photodiodes with low electric field in the low-bandgap InAsP segment and high electric field in the InP multiplication region. Besides clear interband photocurrent signals from the InP and InAsP regions, a strong bias-dependent blueshifted photocurrent peak appears at forward bias offering an interesting novel tunability of the spectral window.

    The presented nanowire-based photodetectors can potentially be grown on silicon substrates due to the small footprint of the nanowires. Successfully developed, novel detector families of low-cost, high performance broadband detectors for optical communication, thermal imaging and solar cell applications can thus be realized.

  • 57.
    Pettersson, Håkan
    Lund University, Lund, Sweden.
    Physics and Technology of Nanowire Infrared Photodetectors2016Ingår i: EMN Photodetectors Meeting, 2016Konferensbidrag (Refereegranskat)
    Abstract [en]

    Over the last two decades there has been a dramatic increase in research activities related to semiconductor nanowires (NWs) due to their exciting prospects for implementation of novel high-performance electronics and photonics compatible with main-stream silicon technology.  In this talk, I will give an overview of our research efforts on infrared photodetectors based on InP/InAsP semiconductor NWs. I will discuss growth, processing and characterization of both single NW devices and large square millimeter array devices comprising millions of NWs connected in parallel. The electrical data generally display excellent rectifying behavior with small leakage currents. From optical measurements, combined with modeling, we conclude that the photocurrent generation depends strongly on the geometry and doping of the NW devices. Properly designed, the absorption of IR radiation in array devices can be significantly enhanced by nanophotonic resonances induced by the geometry and spatially matched to the position of the embedded p-n junctions in the NWs yielding high-efficiency photovoltaics. We have also carried out in-depth studies of InP NW arrays with multiple enclosed axial InAsP quantum wells for broadband and thermal imaging applications. Finally, I will discuss our recent research efforts targeting single InP/InAsP NW avalanche photodetectors with separate absorption and multiplication regions. The presented photodetectors can potentially be grown on cheap silicon substrates due to the small footprint of the NWs. Successfully developed, novel low-cost and high-performance detector families for optical communication, thermal imaging and solar cell applications can be realized.

  • 58.
    Pettersson, Håkan
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS), Tillämpad matematik och fysik (MPE-lab). Lund University, Lund, Sweden.
    Physics and Technology of Nanowire Photodetectors2017Ingår i: 2017 Technical Summaries: OPTP, 2017, s. 279-279Konferensbidrag (Refereegranskat)
    Abstract [en]

    Over the last two decades there has been a dramatic increase in research activities related to semiconductor nanowires (NWs) due to their exciting prospects for implementation of novel high-performance electronics and photonics compatible with main-stream silicon technology.  In this talk, I will give an overview of our research efforts on infrared photodetectors based on InP/InAsP semiconductor NWs. I will discuss growth, processing and characterization of both single NW devices and large square millimeter array devices comprising millions of NWs connected in parallel. The electrical data generally display excellent rectifying behavior with small leakage currents. From optical measurements, combined with modeling, we conclude that the photocurrent generation depends strongly on the geometry and doping of the NW devices. Properly designed, the absorption of IR radiation in array devices can be significantly enhanced by nanophotonic resonances induced by the geometry and spatially matched to the position of the embedded p-n junctions in the NWs yielding high-efficiency photovoltaics. We have also carried out in-depth studies of InP NW arrays with multiple enclosed axial InAsP quantum wells for broadband and thermal imaging applications. Finally, I will discuss our recent research efforts targeting single InP/InAsP NW avalanche photodetectors with separate absorption and multiplication regions. The presented photodetectors can potentially be grown on cheap silicon substrates due to the small footprint of the NWs. Successfully developed, novel low-cost and high-performance detector families for optical communication, thermal imaging and solar cell applications can be realized.

  • 59.
    Pettersson, Håkan
    et al.
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS), Tillämpad matematik och fysik (MPE-lab).
    Bordag, Michael
    Leipzig University, Leipzig, Germany.
    Ribayrol, Aline
    Lund University, Lund, Sweden.
    Conache, Gabriela
    Lund University, Lund, Sweden.
    Fröberg, Linus
    Lund University, Lund, Sweden.
    Samuelson, Lars
    Lund University, Lund, Sweden.
    Montelius, Lars
    Lund University, Lund, Sweden.
    Shear stress measurements on InAs nanowires by AFM manipulation2007Ingår i: Bulletin of the American Physical Society, ISSN 0003-0503, Vol. 52, nr 1Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, we report on a novel approach to measure shear stress between elastic nanowires and a SiO2 surface. The method is based on the fact that the curvature of an elastically deformed nanowire pinned to a flat surface contains information about the maximal static friction force, i.e., the shear stress between the wire and the surface. At rest, the deformed wire is kept in equilibrium by counterbalancing static friction forces and restoring elastic forces. In the present work, InAs nanowires are bent in a controlled manner using the tip of an atomic force microscope (AFM). After the manipulation, the curvature of the most bent state can be determined from AFM micrographs. Assuming bulk values for the Young’s modulus, the shear stress can be obtained from straight- forward analyses according to standard theory of elasticity. 

  • 60.
    Pettersson, Håkan
    et al.
    Högskolan i Halmstad, Sektionen för Informationsvetenskap, Data– och Elektroteknik (IDE), Halmstad Embedded and Intelligent Systems Research (EIS), Tillämpad matematik och fysik (MPE-lab).
    Conache, Gabriela
    Högskolan i Halmstad, Sektionen för Informationsvetenskap, Data– och Elektroteknik (IDE), Halmstad Embedded and Intelligent Systems Research (EIS), Tillämpad matematik och fysik (MPE-lab).
    Gray, Struan M.
    Lund University, Lund, Sweden.
    Bordag, Michael
    Leipzig University, Leipzig, Germany.
    Ribayrol, Aline
    Solid State Physics, Lund University, Lund, Sweden.
    Fröberg, Linus
    Solid State Physics, Lund University, Lund, Sweden.
    Samuelson, Lars
    Solid State Physics, Lund University, Lund, Sweden.
    Montelius, Lars
    Solid State Physics, Lund University, Lund, Sweden.
    Friction measurements on InAs NWs by AFM manipulation2008Konferensbidrag (Refereegranskat)
    Abstract [en]

    We discuss a new approach to measure the friction force between elastically deformed nanowires and a surface. The wires are bent, using an AFM, into an equilibrium shape determined by elastic restoring forces within the wire and friction between the wire and the surface. From measurements of the radius of curvature of the bent wires, elasticity theory allows the friction force per unit length to be calculated. We have studied friction properties of InAs nanowires deposited on SiO2, silanized SiO2 and Si3N4 substrates. The wires were typically from 0.5 to a few microns long, with diameters varying between 20 and 80 nm. Manipulation is done in a `Retrace Lift' mode, where feedback is turned off for the reverse scan and the tip follows a nominal path. The effective manipulation force during the reverse scan can be changed by varying an offset in the height of the tip over the surface. We will report on interesting static- and sliding friction experiments with nanowires on the different substrates, including how the friction force per unit length varies with the diameter of the wires.

  • 61.
    Pettersson, Håkan
    et al.
    Högskolan i Halmstad, Sektionen för Informationsvetenskap, Data– och Elektroteknik (IDE), Halmstad Embedded and Intelligent Systems Research (EIS), Tillämpad matematik och fysik (MPE-lab).
    Liu, Ruisheng S.
    Högskolan i Halmstad, Sektionen för Informationsvetenskap, Data– och Elektroteknik (IDE), Halmstad Embedded and Intelligent Systems Research (EIS), Tillämpad matematik och fysik (MPE-lab).
    Suyatin, Dmitry
    Avdelningen för Fasta Tillståndets Fysik (FTF), Lunds Universitet.
    Samuelson, Lars
    Avdelningen för Fasta Tillståndets Fysik (FTF), Lunds Universitet.
    Assembling ferromagnetic single-electron transistors by atomic force microscopy2008Ingår i: Nanostructures in electronics and photonics / [ed] Rahman, Faiz, Singapore: Pan Stanford Publishing, 2008, s. 29-40Kapitel i bok, del av antologi (Refereegranskat)
  • 62.
    Pettersson, Håkan
    et al.
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS). Solid State Physics and the Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Liu, Ruisheng S.
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS), Tillämpad matematik och fysik (MPE-lab). Solid State Physics and the Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Suyatin, Dmitry
    Solid State Physics and the Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Samuelson, Lars
    Solid State Physics and the Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Assembling ferromagnetic single-electron transistors with atomic force microscopy2008Ingår i: Nanostructures in Electronics and Photonics / [ed] Faiz Rahman, London: Pan Stanford Publishing, 2008, s. 29-40Kapitel i bok, del av antologi (Övrigt vetenskapligt)
    Abstract [en]

    Ferromagnetic Single Electron Transistors (F-SETs) comprise ferromagnetic electrodes connected to a ferromagnetic- or non-magnetic central island via tunnel barriers. These devices are important for studies of spin-transport physics in confined structures. Here we describe the development of a novel type of AFMassembled nano-scale F-SETs suitable for spin-transport investigations at temperatures above 4.2 K. The ingenious fabrication technique means that their electrical characteristics can be tuned in real-time during the fabrication sequence by re-positioning the central island with Ångström precision. © 2008 by Pan Stanford Publishing Pte. Ltd. All rights reserved.

  • 63.
    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(+) photodetectors2012Ingår i: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 23, nr 13, artikel-id 135201Artikel i tidskrift (Refereegranskat)
    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.

  • 64.
    Pham, Thien Viet
    et al.
    Energy Research Institute at NTU (ERIatN), Singapore, Singapore.
    Rao, Manohar
    Energy Research Institute at NTU (ERIatN), Singapore, Singapore.
    Andreasson, Björn Pererik
    Energy Research Institute at NTU (ERIatN), Singapore, Singapore.
    Peng, Yuan
    School of Material Science and Engineering, Nanyang Technological University, Singapore, Singapore.
    Wang, Junling
    School of Material Science and Engineering, Nanyang Technological University, Singapore, Singapore.
    Jinesh, K. B.
    Energy Research Institute at NTU (ERIatN), Singapore, Singapore.
    Photocarrier generation in CuxO thin films deposited by radio frequency sputtering2013Ingår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 102, nr 3, s. Article number: 032101-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Copper oxides (CuxO) thin films were deposited using radio frequency (RF) sputtering on glass substrates. By tuning the argon (Ar) partial pressure during deposition, cuprous oxide (Cu2O), cupric oxide (CuO), or their mixed phase could be achieved. Drastic variations in the Hall mobility, hole density, and resistivity of the samples were observed due to the presence of different phases in the films. Kelvin probe studies indicate that the photo-generated carriers have lower recombination rate in pure Cu 2O phase. This was further validated by transient absorption measurements, where the estimated carrier lifetime for Cu2O was much larger that other phases. © 2013 American Institute of Physics.

  • 65.
    Sauer, Vincent T. K.
    et al.
    National Institute for Nanotechnology, Edmonton, Alberta, Canada & University of Alberta, Edmonton, Alberta, Canada.
    Diao, Zhu
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS), Tillämpad matematik och fysik (MPE-lab). National Institute for Nanotechnology, Edmonton, Alberta, Canada & University of Alberta, Edmonton, Alberta, Canada.
    Westwood-Bachman, Jocelyn N.
    National Institute for Nanotechnology, Edmonton, Alberta, Canada & University of Alberta, Edmonton, Alberta, Canada.
    Freeman, Mark R.
    National Institute for Nanotechnology, Edmonton, Alberta, Canada & University of Alberta, Edmonton, Alberta, Canada.
    Hiebert, Wayne K.
    National Institute for Nanotechnology, Edmonton, Alberta, Canada & University of Alberta, Edmonton, Alberta, Canada.
    Single laser modulated drive and detection of a nano-optomechanical cantilever2017Ingår i: AIP Advances, ISSN 2158-3226, E-ISSN 2158-3226, Vol. 7, nr 1, artikel-id 015115Artikel i tidskrift (Refereegranskat)
  • 66.
    Shang, Xianjung
    et al.
    State Key Laboratory for Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing, China.
    Yu, Ying
    State Key Laboratory for Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing, China.
    Li, Mifeng
    State Key Laboratory for Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing, China.
    Wang, Lijuan
    State Key Laboratory for Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing, China.
    Zha, Guowei
    State Key Laboratory for Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing, China.
    Ni, Haiqiao
    State Key Laboratory for Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing, China.
    Pettersson, Håkan
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS), Tillämpad matematik och fysik (MPE-lab).
    Fu, Ying
    Science for Life Laboratory, Department of Applied Physics, Royal Institute of Technology, Stockholm, Sweden.
    Niu, Zhichuan
    State Key Laboratory for Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing, China.
    Effect of tunable dot charging on photoresponse spectra of GaAs p-i-n diode with InAs quantum dots2015Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 118, nr 24, s. 244503-1-244503-9, artikel-id 244503Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Quantum dots (QDs)-embedded photodiodes have demonstrated great potential on detectors. A modulation of QD charging opens intriguing possibilities for adaptive sensing with bias-tunable detector characteristics. Here, we report on a p-i-n GaAs photodiode with InAs QDs whose charging is tunable due to unintentional Be diffusion and trap-assisted tunneling of holes, from bias- and temperature (T)-dependent photocurrent spectroscopy. For the sub-bandgap spectra, the T-dependent relative intensities "QD-s/WL" and "WL/GaAs" (WL: wetting layer) reflect a dominant tunneling under -0.9 V (trap-assisted tunneling from the top QDs) and a dominant thermal escape under -0.2 ~ 0.5 V (from the bottom QDs since the top ones are charged and inactive for optical absorption) from QD s-state, a dominant tunneling from WL and an enhanced QD charging at > 190 K (related to trap level ionization). For the above-bandgap spectra, the degradation of the spectral profile (especially that near GaAs bandedge) as the bias and T tune (especially under -0.2 ~ 0.2 V and at > 190 K) can be well explained by the enhanced photoelectron capture in QDs with tunable charging; the dominant spectral profile with no degradation under 0.5 V is due to a saturated electron capture in charged QDs (i.e. charging neutralization). QD level simulation and schematic bandstructures help to understand these effects. © 2015 AIP Publishing LLC

  • 67.
    Sizhen, Lan
    et al.
    Högskolan i Halmstad, Sektionen för Informationsvetenskap, Data– och Elektroteknik (IDE).
    Lian, Shen
    Högskolan i Halmstad, Sektionen för Informationsvetenskap, Data– och Elektroteknik (IDE).
    Microwave Components Based on Magnetic Wires2010Självständigt arbete på avancerad nivå (magisterexamen), 40 poäng / 60 hpStudentuppsats (Examensarbete)
    Abstract [en]

    With  the  continuous  advances  in  microwave  technology,  microwave  components  and  related magnetic materials become more important in industrial environment. In order to further develop the microwave components, it is of interest to find new kinds of technologies and materials. Here, we  introduce  a  new  kind  of  material  --  amorphous  metallic  wires  which  could  be  used  in microwave  components,  and  use  these  wires  to  design  new  kinds  of  attenuators.  Based  on  the fundamental  magnetic  properties  of  amorphous  wires  and  transmission  line  theory,  we  design  a series of experiments focusing on these wires, and analyze all the experimental results.    Experimental  results  show  that  incident  and  reflected  signals  produce  interference  and  generate standing  waves  along  the  wire.  At  given  frequency,  the  insertion  attenuation  S21 [dB]  of  an amorphous wire increases monotonically with dc bias current. The glass cover will influence the  magnetic  domain  structure  in  amorphous  metallic  wires.  Therefore,  it  will  affect  the circumference  permeability  and  change  the  signal  attenuation.  It  is  necessary  to  achieve  the impedance  matching  by  coupling  to  an  inductor  and  a  capacitor  in  the  circuit.  The  impedance matching  makes  the  load  impedance  close  to  the  characteristic  impedance  of  transmission  line. The magnetic wire-based attenuator designed in this thesis work are characterized and compared to conventional pin-diode attenuator.

  • 68.
    Smylie, M. P.
    et al.
    Materials Science Division, Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, IL 60439, United States.
    Willa, K.
    Materials Science Division, Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, IL 60439, United States.
    Bao, J. -K
    Materials Science Division, Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, IL 60439, United States.
    Ryan, K.
    Department of Physics, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States.
    Islam, Z.
    Advanced Photon Source, Argonne National Laboratory, 9700 S. Cass Avenue, Lemont, IL 60439, United States.
    Claus, H.
    Materials Science Division, Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, IL 60439, United States.
    Simsek, Y.
    Materials Science Division, Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, IL 60439, United States.
    Diao, Zhu
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS), Tillämpad matematik och fysik (MPE-lab).
    Rydh, A.
    Department of Physics, Stockholm University, Stockholm, SE-106 91, Sweden.
    Koshelev, A. E.
    Materials Science Division, Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, IL 60439, United States.
    Kwok, W. -K
    Materials Science Division, Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, IL 60439, United States.
    Chung, D. Y.
    Materials Science Division, Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, IL 60439, United States.
    Kanatzidis, M. G.
    Materials Science Division, Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, IL 60439, United States.
    Welp, U.
    Materials Science Division, Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, IL 60439, United States.
    Anisotropic superconductivity and magnetism in single-crystal RbEuFe4As42018Ingår i: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 98, nr 10, artikel-id 104503Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We investigate the anisotropic superconducting and magnetic properties of single-crystal RbEuFe4As4 using magnetotransport and magnetization measurements. We determine a magnetic ordering temperature of the Eu moments of Tm=15K and a superconducting transition temperature of Tc=36.8K. The superconducting phase diagram is characterized by high upper critical field slopes of -70 and -42 kG/K for in-plane and out-of-plane fields, respectively, and a surprisingly low superconducting anisotropy of Γ=1.7. Ginzburg-Landau parameters of κc∌67 and κab∌108 indicate extreme type-II behavior. These superconducting properties are in line with those commonly seen in optimally doped Fe-based superconductors. In contrast, Eu magnetism is quasi-two dimensional (2D), as evidenced by highly anisotropic in-plane and out-of-plane exchange constants of 0.6 K and <0.04 K. A consequence of the quasi-2D nature of the Eu magnetism are strong magnetic fluctuation effects, a large suppression of the magnetic ordering temperature as compared to the Curie-Weiss temperature, and a kinklike anomaly in the specific heat devoid of any singularity. Magnetization curves reveal a clear magnetic easy-plane anisotropy with in-plane and out-of-plane saturation fields of 2 and 4 kG. © 2018 American Physical Society.

  • 69.
    Stepanova, K. V.
    et al.
    Petrozavodsk State University, Petrozavodsk, Russia.
    Yakovleva, N. M.
    Petrozavodsk State University, Petrozavodsk, Russia.
    Kokatev, Alexander N.
    Petrozavodsk State University, Petrozavodsk, Russia.
    Pettersson, Håkan
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS), Tillämpad matematik och fysik (MPE-lab).
    Influence of annealing on the structure of nanoporous oxide films on the surface of titanium‒aluminum powder alloy2016Ingår i: Journal of Surface Investigation. X-ray, Synchrotron and Neutron Techniques, ISSN 1027-4510, Vol. 10, nr 5, s. 933-941Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Oxide films obtained during anodization of Ti‒40% Al sintered powder samples in fluorine-containing electrolytes are investigated. With scanning electron microscopy and X-ray phase analysis, it is demonstrated that an X-ray amorphous nanoporous anodic oxide film is formed on the surface of the powder microparticles under optimal anodization conditions. After annealing at T = 1093 K in air and vacuum (10‒2 Pa), the oxide films are revealed to crystallize with its regular porous structure retained. The composition of the polycrystalline anodic-oxide films annealed in air is a mixture involving TiO2 (anatase and rutile) and α- and γ-Al2O3 phases and Ti2O3 and Al2TiO5 traces. The vacuum annealing process makes it possible to identify TiO2, in which anatase is the main phase, α- and γ-Al2O3, and Ti2O3 and TiO traces. However, rutile is not revealed. The presented results indicate that the application of the anodic nanostructuring of Ti‒40% Al powders is promising for the obtainment of new photocatalytic active nanomaterials. © 2016, Pleiades Publishing, Ltd.

  • 70.
    Trägårdh, Johanna
    et al.
    Solid State Physics, Lund University, Lund, Sweden.
    Persson, Ann
    Solid State Physics, Lund University, Lund, Sweden.
    Hessman, Dan
    Solid State Physics, 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).
    Landin, Lars
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS), Tillämpad matematik och fysik (MPE-lab).
    Samuelson, Lars
    Solid State Physics, Lund University, Lund, Sweden.
    Photocurrent Spectroscopy on Single Heterostructure Nanowires2005Ingår i: Symposium EE: Progress in Semiconductor Materials V-Novel Materials and Electronic and Optoelectronic Applications, 2005, s. 753-753Konferensbidrag (Refereegranskat)
  • 71.
    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
    Högskolan i Halmstad, Akademin för informationsteknologi, 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
    Högskolan i Halmstad, Akademin för informationsteknologi, 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 Nanowires2012Ingår i: Journal of Nanotechnology, ISSN 1687-9503, E-ISSN 1687-9511, Vol. 2012, artikel-id 480813Artikel i tidskrift (Refereegranskat)
    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.

  • 72.
    Zalden, Peter
    et al.
    Stanford PULSE Institute, SLAC National Accelerator Laboratory, Menlo Park, USA & Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, USA & European XFEL, Schenefeld, Germany.
    Quirin, Florian
    Faculty of Physics and Center for Nanointegration Duisburg-Essen (CENIDE), University of Duisburg-Essen, Duisburg, Germany.
    Schumacher, Mathias
    Institut für Theoretische Festkörperphysik, JARA-FIT and JARA-HPC, RWTH Aachen University, Aachen, Germany.
    Siegel, Jan
    Instituto de Optica, Consejo Superior de Investigaciones Científicas, Madrid, Spain.
    Wei, Shuai
    I. Physikalisches Institut and JARA-FIT, RWTH Aachen, Aachen, Germany.
    Koc, Azize
    Faculty of Physics and Center for Nanointegration Duisburg-Essen (CENIDE), University of Duisburg-Essen, Duisburg, Germany & Institut für Physik und Astronomie, Universität Potsdam, Potsdam, Germany.
    Nicoul, Matthieu
    Faculty of Physics and Center for Nanointegration Duisburg-Essen (CENIDE), University of Duisburg-Essen, Duisburg, Germany.
    Trigo, Mariano
    Stanford PULSE Institute, SLAC National Accelerator Laboratory, Menlo Park, USA & Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, USA.
    Andreasson, Björn Pererik
    Department of Physics, Lund University, Lund, Sweden.
    Enquist, Henrik
    Department of Physics, Lund University, Lund, Sweden.
    Shu, Michael
    Department of Applied Physics, Stanford University, Stanford, USA.
    Pardini, Tommaso
    Lawrence Livermore National Laboratory, Livermore, USA.
    Chollet, Matthieu
    Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, USA.
    Zhu, Diling
    Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, USA.
    Lemke, Henrik
    Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, USA & Paul Scherrer Institute, Villigen, Switzerland.
    Ronneberger, Ider
    Institut für Theoretische Festkörperphysik, JARA-FIT and JARA-HPC, RWTH Aachen University, Aachen, Germany.
    Larsson, Jörgen
    Department of Physics, Lund University, Lund, Sweden.
    Lindenberg, Aaron
    Stanford PULSE Institute, SLAC National Accelerator Laboratory, Menlo Park, USA & Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, USA & Department of Materials Science and Engineering, Stanford University, Stanford, USA.
    Fischer, Henry
    Institut Laue-Langevin, Grenoble, France.
    Hau-Riege, Stefan
    Lawrence Livermore National Laboratory, Livermore, USA.
    Reis, David
    Stanford PULSE Institute, SLAC National Accelerator Laboratory, Menlo Park, USA & Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, USA.
    Mazzarello, Riccardo
    Institut für Theoretische Festkörperphysik, JARA-FIT and JARA-HPC, RWTH Aachen University, Aachen, Germany.
    Wuttig, Matthias
    I. Physikalisches Institut and JARA-FIT, RWTH Aachen, Aachen, Germany & PGI 10 (Green IT), Forschungszentrum Jülich, Jülich, Germany.
    Sokolowski-Tinten, Klaus
    Faculty of Physics and Center for Nanointegration Duisburg-Essen (CENIDE), University of Duisburg-Essen, Duisburg, Germany.
    Femtosecond x-ray diffraction reveals a liquid–liquid phase transition in phase-change materials2019Ingår i: Science, ISSN 0036-8075, E-ISSN 1095-9203, Vol. 364, nr 6445, s. 1062-1067Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In phase-change memory devices, a material is cycled between glassy and crystalline states. The highly temperature-dependent kinetics of its crystallization process enables application in memory technology, but the transition has not been resolved on an atomic scale. Using femtosecond x-ray diffraction and ab initio computer simulations, we determined the time-dependent pair-correlation function of phase-change materials throughout the melt-quenching and crystallization process. We found a liquid–liquid phase transition in the phase-change materials Ag4In3Sb67Te26 and Ge15Sb85 at 660 and 610 kelvin, respectively. The transition is predominantly caused by the onset of Peierls distortions, the amplitude of which correlates with an increase of the apparent activation energy of diffusivity. This reveals a relationship between atomic structure and kinetics, enabling a systematic optimization of the memory-switching kinetics. © 2019 American Association for the Advancement of Science.

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