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  • 1.
    Aghaeipour, Mahtab
    Lund University, Lund, Sweden.
    Tailoring the Optical Response of III-V Nanowire Arrays2017Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Semiconductor nanowires show a great deal of promise for applications in a wide range of important fields, including photovoltaics, biomedicine, and information technology. Developing these exciting applications is strongly dependent on understanding the fundamental properties of nanowires, such as their optical resonances and absorption spectra. In this thesis we explore optical absorption spectra of arrays of vertical III-V nanowires with a special emphasis on structures optimized to enhance absorption in the solar spectrum. First, we analyze experimentally determined absorption spectra of both indium phosphide (InP) and gallium phosphide (GaP) nanowire arrays. The study provides an intuitive understanding of how the observed absorption resonances in the nanowires may be tuned as a function of their geometrical parameters and crystal structure. As a consequence, the spectral position of absorption resonances can be precisely controlled through the nanowire diameter. However, the results highlight how the blue-shift in the optical absorption resonances as the diameter of the nanowires decreases comes to a halt at low diameters. The stop point is related to the behavior of the refractive indices of the nanowires. The wavelength of the stop is different for nanowire polytypes of similar dimensions due to differences in their refractive indices. We then present a theoretical argument that it is important to consider symmetry properties when tailoring the optical modes excited in the nanowires for enhanced absorption. We show that absorption spectra may be enhanced compared to vertical nanowires at normal incidence by tilting the nanowires with normal incidence light, or by using off-normal incidence with vertical nanowires. This is because additional optical modes inside the nanowires are excited when the symmetry is broken. Looking forward to omnidirectional applications, we consider branched nanowires as a way to enhance the absorption spectra at normal incidence by taking advantage of simultaneous excitation of the spectrally different optical modes in the branches and the stems. Third, we describe in theoretical terms how integrating distributed Bragg reflectors (DBRs) with the nanowires can improve absorption spectra compared to conventional nanowires. DBRs provide a way to employ light trapping mechanisms which increases the optical path length of the excited modes and thereby improves the absorption of the excited modes. At normal incidence, DBR-nanowires improve the absorption efficiency to 78%, compared to 72% for conventional nanowires. We show that the efficiency is increased to 85% for an off-normal incident angle of 50˚. Overall, our results show that studies of optical resonances in nanowires that take the light-matter interaction into account provide opportunities to develop novel optical and optoelectronic functionalities in nanoscience and nanotechnology.

  • 2.
    Aghaeipour, Mahtab
    et al.
    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). Lund University, Lund, Sweden.
    Enhanced broadband absorption in nanowire arrays with integrated Bragg reflectors2018Inngår i: Nanophotonics, E-ISSN 2192-8614, Vol. 7, nr 5, s. 819-825Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A near-unity unselective absorption spectrum is desirable for high-performance photovoltaics. Nanowire arrays are promising candidates for efficient solar cells due to nanophotonic absorption resonances in the solar spectrum. The absorption spectra, however, display undesired dips between the resonance peaks. To achieve improved unselective broadband absorption, we propose to enclose distributed Bragg reflectors (DBRs) in the bottom and top parts of indium phosphide (InP) nanowires, respectively. We theoretically show that by enclosing only two periods of In0.56Ga0.44As/InPDBRs, an unselective 78% absorption efficiency (72% for nanowires without DBRs)is obtained at normal incidence in the spectral range from 300 nm to 920 nm. Under oblique light incidence, the absorption efficiency is enhanced up to about 85% at an incidence angle of 50º. By increasing the number of DBR periods from two to five, the absorption efficiency is further enhanced up to 95% at normal incidence. In this work we calculated optical spectra for InP nanowires, but the results are expected to be valid for other direct band gap III-V semiconductor materials. We believe that our proposed idea of integrating DBRs in nanowires offers great potential for high-performance photovoltaic applications. ©2018 Håkan Pettersson et al., published by De Gruyter, Berlin/Boston.

  • 3.
    Aghaeipour, Mahtab
    et al.
    Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Pettersson, Håkan
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS).
    Enhanced optical absorption in nanowires over a desire range of wavelengths2017Inngår i: MOC2017 : technical digest of the Twenty-Second Microoptics Conference: November 19-22, 2017, Institute of Industrial Science, The University of Tokyo, Japan, 2017, Vol. 2017-November, s. 360-361Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Engineering optical absorption in nanowires, over a desire range of wavelengths is of importance to design high-performance nanowire-based photovoltaics. To this end, we integrate the nanowires with distributed Bragg reflectors to enhance absorption spectra of the nanowires and relate the consequent enhancement to increasing the optical path lengths of the modes. © 2017 The Japan Society of Applied Physics.

  • 4.
    Aghaeipour, Mahtab
    et al.
    Lund University, Lund, Sweden.
    Pistol, Mats-Erik
    Lund University, Lund, Sweden.
    Pettersson, Håkan
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS). Lund University, Lund, Sweden.
    Comparative study of absorption efficiency of inclined and vertical InP nanowires2017Inngår i: Physics, Simulation, and Photonic Engineering of Photovoltaic Devices VI / [ed] A. Freundlich, L. Lombez, M. Sugiyama, Bellingham, WA: SPIE - International Society for Optical Engineering, 2017, Vol. 10099, artikkel-id UNSP 100990SKonferansepaper (Fagfellevurdert)
    Abstract [en]

    Geometrically designed III-V nanowire arrays are promising candidates for optoelectronics due to their possibility to excite nanophotonic resonances in absorption spectra. Strong absorption resonances can be obtained by proper tailoring of nanowire diameter, length and pitch. Such enhancement of the light absorption is, however, accompanied by undesired resonance dips at specific wavelengths. In this work, we theoretically show that tilting of the nanowires mitigates the absorption dips by exciting strong Mie resonances. In particular, we derive a theoretical optimum inclination angle of about 30 degrees at which the inclined nanowires gain 8% in absorption efficiency compared to vertically standing nanowires in a spectral region matching the intensity distribution of the sun. The enhancement is due to engineering the excited modes inside the nanowires regarding the symmetry properties of the nanowire/light system without increasing the absorbing material. We expect our results to be important for nanowire-based photovoltaic applications. © 2017 SPIE.

  • 5.
    Aghaeipour, Mahtab
    et al.
    Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Pistol, Mats-Erik
    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.
    Considering Symmetry Properties of InP Nanowire/Light Incidence Systems to Gain Broadband Absorption2017Inngår i: IEEE Photonics Journal, ISSN 1097-5764, E-ISSN 1943-0655, Vol. 9, nr 3, artikkel-id 4501310Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Geometrically designed III-V nanowire arrays are promising candidates for disruptive optoelectronics due to the possibility of obtaining a strongly enhanced absorption resulting from nanophotonic resonance effects. With normally incident light on such vertical nanowire arrays, the absorption spectra exhibit peaks that originate from excitation of HE1m waveguide modes in the constituent nanowires. However, the absorption spectra typically show dips between the absorption peaks. Conventionally, such weak absorption has been counteracted by either making the nanowires longer or by decreasing the pitch of the array, both alternatives effectively increasing the volume of absorbing material in the array. Here, we first study two approaches for compensating the absorption dips by exciting additional Mie resonances: 1) oblique light incidence on vertical InP nanowire arrays and 2) normal light incidence on inclined InP nanowire arrays. We then show that branched nanowires offer a novel route to achieve broadband absorption by taking advantage of simultaneous excitations of Mie resonances in the branches and guided HE1m modes in the stem. Finite element method calculations show that the absorption efficiency is enhanced from 0.72 for vertical nanowires to 0.78 for branched nanowires under normal light incidence. Our work provides new insight for the development of novel efficient photovoltaics with high efficiency and reduced active material volume.

  • 6.
    Ahmed, Rizwan
    et al.
    Högskolan i Halmstad, Sektionen för Informationsvetenskap, Data– och Elektroteknik (IDE).
    Abbas, Shahid
    Högskolan i Halmstad, Sektionen för Informationsvetenskap, Data– och Elektroteknik (IDE).
    Electrical and Optical Characteristics of InP Nanowires based p-i-n Photodetectors2010Independent thesis Advanced level (degree of Master (One Year)), 10 poäng / 15 hpOppgave
    Abstract [en]

    Photodetectors are a kind of semiconductor devices that convert incoming light to an electrical signal. Photodetectors are classified based on their different structure, fabrication technology, applications and different sensitivity. Infrared photodetectors are widely used in many applications such as night vision, thermal cameras, remote temperature sensing, and medical diagnosis etc.

     

    All detectors have material inside that is sensitive to incoming light. It will absorb the photons and, if the incoming photons have enough energy, electrons will be excited to higher energy levels and if these electrons are free to move, under the effect of an external electric field, a photocurrent is generated.

     

    In this project Fourier Transform Infrared (FT-IR) Spectroscopy is used to investigate a new kind of photodiodes that are based on self-assembled semiconductor nanowires (NWs) which are grown directly on the substrate without any epi-layer. The spectrally resolved photocurrent (at different applied biases) and IV curves (in darkness and illumination) for different temperatures have been studied respectively. Polarization effects (at low and high Temperatures) have been investigated.  The experiments are conducted for different samples with high concentration of NWs as well as with lower concentration of NWs in the temperature range from 78 K (-195ºC) to 300 (27ºC). These photodiodes are designed to work in near infrared (NIR) spectral range.

     

    The results show that the NW photodetectors indeed are promising devices with fairly high break down voltage, change of photocurrent spectra with polarized light, low and constant reverse saturation current (Is). The impact of different polarized light on photocurrent spectra has been investigated and an attempt has been made to clarify the observed double peak of InP photocurrent spectrum. Our investigations also include a comparison to a conventional planar InP p-i-n photodetector.

     

  • 7.
    Andreasson, Björn Pererik
    et al.
    Swiss Light Source, Paul Scherrer Institut, Villigen, Switzerland.
    Janousch, M.
    Swiss Light Source, Paul Scherrer Institut, Villigen, Switzerland.
    Staub, U.
    Swiss Light Source, Paul Scherrer Institut, Villigen, Switzerland.
    Meijer, G. I.
    IBM Research, Zurich Research Laboratory, Rüschlikon, Switzerland.
    Spatial distribution of oxygen vacancies in Cr-doped SrTiO3 during an electric-field-driven insulator-to-metal transition2009Inngår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 94, nr 1, s. Article number: 013513-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Spatially resolved x-ray fluorescence maps are presented that show the introduction and the evolution of oxygen vacancies in chromium-doped strontium titanate during an electric-field-driven insulator-to-metal transition. The vacancies are introduced at the anode and diffuse through the crystal toward the cathode. The spatial distribution of vacancies is explained by a model describing the electrical breakdown as a percolation process. Strong differences in the vacancy distribution were found when the transition took place in air and in a hydrogen-enriched atmosphere. In air, the vacancies disappeared from the surface, whereas in the reducing hydrogen atmosphere, they remained at the surface. © 2009 American Institute of Physics.

  • 8.
    Andreasson, Björn Pererik
    et al.
    Swiss Light Source, Paul Scherrer Institut, Villigen, Switzerland.
    Janousch, M.
    Swiss Light Source, Paul Scherrer Institut, Villigen, Switzerland.
    Staub, U.
    Swiss Light Source, Paul Scherrer Institut, Villigen, Switzerland.
    Meijer, G. I.
    IBM Research, Zurich Research Laboratory, Rüschlikon, Switzerland.
    Delley, B.
    Swiss Light Source, Paul Scherrer Institut, Villigen, Switzerland.
    Resistive switching in Cr-doped SrTiO3: An X-ray absorption spectroscopy study2007Inngår i: Materials Science & Engineering: B. Solid-state Materials for Advanced Technology, ISSN 0921-5107, E-ISSN 1873-4944, Vol. 144, nr 1-3, s. 60-63Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    X-ray absorption spectroscopy was used to study the microscopic origin of conductance and resistive switching in chromium-doped strontium titanate (Cr:SrTiO3). Differences in the X-ray absorption near edge spectroscopy (XANES) at the Cr K-edge indicate that the valence of Cr changes from 3+ to 4+ underneath the anode of our sample device after the application of an electric field. Spatially resolved X-ray fluorescence microscopy (μ-XRF) maps show that the Cr4+ region retracts from the anode-Cr:SrTiO3 interface after a conducting state has been achieved. This interface region is studied with extended X-ray absorption fine structure (EXAFS) and the results are compared with structural parameters obtained from density functional theory (DFT) calculations. They confirm that oxygen vacancies which are localized at the octahedron with a Cr at its center are introduced at the interface. It is proposed that the switching state is not due to a valence change of chromium but caused by changes of oxygen vacancies at the interface. © 2007 Elsevier B.V. All rights reserved.

  • 9.
    Andreasson, Björn Pererik
    et al.
    Swiss Light Source, Paul Scherrer Institut, Villigen, Switzerland.
    Janousch, M.
    Swiss Light Source, Paul Scherrer Institut, Villigen, Switzerland.
    Staub, U.
    Swiss Light Source, Paul Scherrer Institut, Villigen, Switzerland.
    Meijer, G. I.
    IBM Research, Zurich Research Laboratory, Rüschlikon, Switzerland.
    Ramar, A.
    École Polytechnique Fédérale de Lausanne (EPFL), Centre de Recherche en Physique des Plasmas, Association Euratom-Confédération Suisse, Villigen, Switzerland & Center for Electron Nanoscopy, Technical University of Denmark, Lyngby, Denmark.
    Krbanjevic, J.
    École Polytechnique Fédérale de Lausanne (EPFL), Centre de Recherche en Physique des Plasmas, Association Euratom-Confédération Suisse, Villigen, Switzerland.
    Schaeublin, R.
    École Polytechnique Fédérale de Lausanne (EPFL), Centre de Recherche en Physique des Plasmas, Association Euratom-Confédération Suisse, Villigen, Switzerland.
    Origin of oxygen vacancies in resistive switching memory devices2009Inngår i: Journal of Physics, Conference Series, ISSN 1742-6588, E-ISSN 1742-6596, Vol. 190, s. Article number: 012074-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The resistive switching state in Cr-doped SrTiO3 was induced by applying an electric field. This was done in ambient air and in an atmosphere of H2/Ar. The distribution of the thereby introduced oxygen vacancies was studied by spatially resolved X-ray fluorescence images. It was concluded that the oxygen vacancies were introduced in the interface between the SrTiO3 and the positively biased electrode. © 2009 IOP Publishing Ltd.

  • 10.
    Andreasson, Björn Pererik
    et al.
    Swiss Light Source, Paul Scherrer Institut, Villigen, Switzerland.
    Janousch, M.
    Swiss Light Source, Paul Scherrer Institut, Villigen, Switzerland.
    Staub, U.
    Swiss Light Source, Paul Scherrer Institut, Villigen, Switzerland.
    Todorova, T.
    Condensed Matter Theory Group, Paul Scherrer Institut, Villigen, Switzerland.
    Delley, B.
    Condensed Matter Theory Group, Paul Scherrer Institut, Villigen, Switzerland.
    Meijer, G. I.
    IBM Research, Zurich Research Laboratory, Rüschlikon, Switzerland.
    Pomjakushina, E.
    Laboratory for Developments and Methods, Paul Scherrer Institut, Villigen, Switzerland.
    Detecting oxygen vacancies in SrTiO3 by 3d transition-metal tracer ions2009Inngår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 80, nr 21, s. Article number: 212103-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    X-ray absorption experiments on 3d transition-metal tracer ions in SrTiO3 are presented. The absorption spectra of the tracer-ion changed upon reduction in the SrTiO3. This change is due to an oxygen vacancy created at the tracer-ion site. This finding is supported by density-functional theory calculations, which prove that the oxygen vacancies preferentially are created at the tracer-ion sites. Using the chemical sensitivity of x-ray absorption spectroscopy, tracer ions can be used to detect oxygen vacancies in SrTiO3 and possibly in other oxide systems. © 2009 The American Physical Society.

  • 11.
    Anokhina, Ksenia
    et al.
    Avd. f. Fasta Tillståndets Fysik, Lunds Universitet, Lund, Sweden.
    Graczyk, Mariousz
    Avd. f. Fasta Tillståndets Fysik, Lunds Universitet, Lund, Sweden.
    Kvennefors, Anders
    Avd. f. Fasta Tillståndets Fysik, Lunds Universitet, Lund, Sweden.
    Montelius, Lars
    Avd. f. Fasta Tillståndets Fysik, Lunds Universitet, Lund, Sweden.
    Maximov, Ivan
    Avd. f. Fasta Tillståndets Fysik, Lunds Universitet, Lund, Sweden.
    Pettersson, Håkan
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS), Tillämpad matematik och fysik (MPE-lab).
    Metal-assisted chemical etching of Si for fabrication of nanoimprint stamps2011Konferansepaper (Fagfellevurdert)
  • 12.
    Berg, Alexander
    et al.
    Lund University, Lund, Sweden.
    Yazdi, Sadegh
    Technical University of Denmark, Lyngby, Denmark.
    Nowzari, Ali
    Lund University, Lund, Sweden.
    Storm, Kristian
    Lund University, Lund, Sweden.
    Jain, Vishal
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS), Tillämpad matematik och fysik (MPE-lab). Lund University, Lund, Sweden.
    Vainorius, Neimantas
    Lund University, Lund, Sweden.
    Samuelson, Lars
    Lund University, Lund, Sweden.
    Wagner, Jakob B.
    Technical University of Denmark, Lyngby, Denmark.
    Borgström, Magnus T.
    Lund University, Lund, Sweden.
    Radial Nanowire Light-Emitting Diodes in the (AlxGa1-x)yIn1-yP Material System2016Inngår i: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 16, nr 1, s. 656-662Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Nanowires have the potential to play an important role for next-generation light-emitting diodes. In this work, we present a growth scheme for radial nanowire quantum-well structures in the AlGaInP material system using a GaInP nanowire core as a template for radial growth with GaInP as the active layer for emission and AlGaInP as charge carrier barriers. The different layers were analyzed by X-ray diffraction to ensure lattice-matched radial structures. Furthermore, we evaluated the material composition and heterojunction interface sharpness by scanning transmission electron microscopy energy dispersive X-ray spectroscopy. The electro-optical properties were investigated by injection luminescence measurements. The presented results can be a valuable track toward radial nanowire light-emitting diodes in the AlGaInP material system in the red/orange/yellow color spectrum. © 2015 American Chemical Society.

  • 13.
    Bordag, Michael
    et al.
    Leipzig University, Institute for Theoretical Physics, Leipzig, Germany.
    Jede, Ralf
    Raith GmbH, Dortmund, Germany.
    Montelius, Lars
    Lunds University, Physics Department, Lund, Sweden.
    Pettersson, Håkan
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS), Tillämpad matematik och fysik (MPE-lab).
    Riu, Jordi
    University Rovira i Vergili, Taragona, Spain.
    Schmucker, Ulrich
    University Rovira i Vergili, Taragona, Spain.
    Zubtsov, Michael
    Fraunhofer Institute for Factory Automation, Magdeburg, Germany.
    Parallel nano-assembly directed by short-range field forces2006Inngår i: Proceedings of the 1st IEEE International Conference on Nano/Micro Engineered and Molecular Systems, Piscataway, United States: IEEE Press, 2006, s. 620-622, artikkel-id 4135031Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We present the ECs Sixth Framework Programme PARNASS project, which stands for 'Parallel nano assembling directed by short-range field forces' and represents a radical innovative approach to fabricating large volumes of hybrid nano electronic devices. The project combines in a synergy the 'top-down' and 'bottom-up' methods addressing one of the challenging physical and engineering problems of the very high accuracy over a large area. An array of specially designed nano-scale force field sources has to be a key part of this innovative approach to large-scale nano manufacturing. © 2006 IEEE.

  • 14.
    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
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS), Tillämpad matematik och fysik (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 Conditions2011Konferansepaper (Fagfellevurdert)
  • 15.
    Conache, Gabriela
    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).
    Gray, Struan M.
    Avd. f. Fasta Tillståndets Fysik, Lunds Universitet, Sweden.
    Ribayrol, Aline
    Avd. f. Fasta Tillståndets Fysik, Lunds Universitet, Sweden.
    Fröberg, Linus
    Avd. f. Fasta Tillståndets Fysik, Lunds Universitet, Sweden.
    Samuelson, Lars
    Avd. f. Fasta Tillståndets Fysik, Lunds Universitet, Sweden.
    Montelius, Lars
    Avd. f. Fasta Tillståndets Fysik, Lunds Universitet, Sweden.
    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).
    Comparative friction measurements of InAs nanowires on three substrates2010Inngår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 108, nr 9, s. 094307-094307-5Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have investigated friction between InAs nanowires and three different substrates: SiO2, fluorosilanized SiO2, and Si3N4. The nanowires were pushed laterally with the tip of an atomic force microscope and the friction force per unit length for both static and sliding friction was deduced from the equilibrium shape of the bent wires. On all three substrates, thick wires showed a difference between sliding and static friction of up to three orders of magnitude. Furthermore, all substrates display a transition to stick-slip motion for nanowires with a diameter of less than about 40 nm. Hydrophobic and hydrophilic substrates display similar friction behavior suggesting that a condensed water layer does not strongly influence our results. The patterns and trends in the friction data are similar for all three substrates, which indicates that they are more fundamental in character and not specific to a single substrate. ©2010 American Institute of Physics.

  • 16.
    Conache, Gabriela
    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). Lund University, Solid State Physics/Nanometer Consortium, Box 118, S-221 00, Lund, Sweden.
    Gray, Struan M.
    Lund University, Solid State Physics/Nanometer Consortium, Box 118, S-221 00, Lund, Sweden.
    Ribayrol, Aline
    Lund University, Solid State Physics/Nanometer Consortium, Box 118, S-221 00, Lund, Sweden.
    Fröberg, Linus
    Lund University, Solid State Physics/Nanometer Consortium, Box 118, S-221 00, Lund, Sweden.
    Samuelson, Lars
    Lund University, Solid State Physics/Nanometer Consortium, Box 118, S-221 00, Lund, Sweden.
    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).
    Montelius, Lars
    Lund University, Solid State Physics/Nanometer Consortium, Box 118, S-221 00, Lund, Sweden.
    Nanowire friction with an applied bias2009Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Recently, we have shown how the friction acting on nanowires pushed across a surface by an AFM tip can be determined by measuring the radius of curvature of the bent wire aŸer manipulation. This technique allows us to study the friction properties of an extended mesoscale contact. Our main focus has been to determine whether such contacts behave like macroscopic objects, in which dišerences between the 'true' and 'apparent' contact areas play a key role and friction varies linearly with the applied normal force, or whether they are more like atomic-scale point contacts, wheremore fundamental processes dominate and friction oŸen is independent of the normal force. In this work we show how the friction between InAs nanowires and an insulating silicon nitride layer on a conductive silicon substrate varies when a DC voltage is applied to the AFM tip during manipulation. e tip charges the capacitor formed by the wire and the grounded silicon back contact, giving rise to attractive Coulomb forces and thus increasing the contact pressure between the wire and the silicon nitride. In this way we can vary the normal force on the sliding surfaces using a single wire, with a constant structure and contact geometry. Using nanowires of about 40-50 nm diameter and a few microns in length we have applied tip voltages in the range +12 to -12 V. Simplemodeling indicates that these voltages su›ce to give similar levels of band-lling and depletion to when the same wires are used in working wrap-gate or back-gate devices. A monotonic increase of the sliding friction with the voltage applied on the tip was observed. is implies that the friction increases with the normal force and that this mesoscopic system behaves more like a macroscopic contact, despite the nanometer size of the contact in the direction of motion.

  • 17.
    Conache, Gabriela
    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).
    Ribayrol, Aline
    Avd. f. Fasta Tillståndets Fysik, Lunds Universitet, Sweden.
    Fröberg, Linus
    Avd. f. Fasta Tillståndets Fysik, Lunds Universitet, Sweden.
    Borgström, Magnus T.
    Avd. f. Fasta Tillståndets Fysik, Lunds Universitet, Sweden.
    Samuelson, Lars
    Avd. f. Fasta Tillståndets Fysik, Lunds Universitet, Sweden.
    Montelius, Lars
    Avd. f. Fasta Tillståndets Fysik, Lunds Universitet, Sweden.
    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).
    Gray, Struan M.
    Avd. f. Fasta Tillståndets Fysik, Lunds Universitet, Sweden.
    Bias-controlled friction of InAs nanowires on a silicon nitride layer studied by atomic force microscopy2010Inngår i: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 82, nr 3Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    By studying how nanowires lying on a surface bend when pushed by an atomic force microscopy tip we are able to measure the friction between them and the substrate. Here, we show how the friction between InAs nanowires and an insulating silicon nitride layer varies when a dc voltage is applied to the tip during manipulation. The bias charges the capacitor formed by the wire and the grounded silicon back contact. Electrostatic forces increase the contact pressure and allow us to tune the friction between the wire and the silicon nitride surface. Using nanowires of about 40-70 nm diameter and a few microns in length we have applied biases in the range +12 to -12 V. A monotonic increase of the sliding friction with voltage was observed. This increase in friction with the normal force implies that the mesoscopic nanowire-surface system behaves like a macroscopic contact, despite the nanometer size of the contact in the direction of motion. The demonstrated bias-controlled friction has potential applications in MEMS/NEMS devices.

  • 18.
    Diao, Zhu
    et al.
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS), Tillämpad matematik och fysik (MPE-lab).
    Sauer, Vincent T. K.
    National Institute for Nanotechnology, Alberta, Canada; Department of Biological Sciences & Department of Electrical and Computer Engineering, University of Alberta, Alberta, Canada.
    Hiebert, Wayne K.
    National Institute for Nanotechnology, Alberta, Canada & Department of Physics, University of Alberta, Alberta, Canada.
    Integrated On-Chip Nano-Optomechanical Systems2017Inngår i: International Journal of High Speed Electronics and Systems, ISSN 0129-1564, Vol. 26, nr 1-2, artikkel-id 1740005Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Recent developments in integrated on-chip nano-optomechanical systems are reviewed. Silicon-based nano-optomechanical devices are fabricated by a two-step process, where the first step is a foundry-enabled photonic circuits patterning and the second step involves in-house mechanical device release. We show theoretically that the enhanced responsivity of near-field optical transduction of mechanical displacement in on-chip nano-optomechanical systems originates from the finesse of the optical cavity to which the mechanical device couples. An enhancement in responsivity of more than two orders of magnitude has been observed when compared side-by-side with free-space interferometry readout. We further demonstrate two approaches to facilitate large-scale device integration, namely, wavelength-division multiplexing and frequency-division multiplexing. They are capable of significantly simplifying the design complexity for addressing individual nano-optomechanical devices embedded in a large array. © 2017 World Scientific Publishing Company.

  • 19.
    Gooth, Johannes
    et al.
    Institute of Nanostructure and Solid State Physics, Universität Hamburg, Hamburg, Germany & IBM Research-Zurich, Rüschlikon, Switzerland.
    Zierold, Robert
    Institute of Nanostructure and Solid State Physics, Universität Hamburg, Hamburg, Germany.
    Sergelius, Philip
    Institute of Nanostructure and Solid State Physics, Universität Hamburg, Hamburg, Germany.
    Hamdou, Bacel
    Institute of Nanostructure and Solid State Physics, Universität Hamburg, Hamburg, Germany.
    Garcia, Javier
    Institute for Metallic Materials, IFW Dresden, Dresden, Germany.
    Damm, Christine
    Institute for Metallic Materials, IFW Dresden, Dresden, Germany.
    Rellinghaus, Bernd
    Institute for Metallic Materials, IFW Dresden, Dresden, Germany.
    Pettersson, Håkan
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS), Tillämpad matematik och fysik (MPE-lab). Division of Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Pertsova, Anna
    Department of Physics and Electrical Engineering, Linnaeus University, Kalmar, Sweden.
    Canali, Carlo
    Department of Physics and Electrical Engineering, Linnaeus University, Kalmar, Sweden.
    Borg, Mattias
    IBM Research-Zurich, Rüschlikon, Switzerland.
    Nielsch, Kornelius
    Institute of Nanostructure and Solid State Physics, Universität Hamburg, Hamburg, Germany & Institute for Metallic Materials, IFW Dresden, Dresden, Germany.
    Local Magnetic Suppression of Topological Surface States in Bi2Te3 Nanowires2016Inngår i: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 10, nr 7, s. 7180-7188Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Locally induced, magnetic order on the surface of a topological insulator nanowire could enable room-temperature topological quantum devices. Here we report on the realization of selective magnetic control over topological surface states on a single facet of a rectangular Bi2Te3 nanowire via a magnetic insulating Fe3O4 substrate. Low-temperature magnetotransport studies provide evidence for local time-reversal symmetry breaking and for enhanced gapping of the interfacial 1D energy spectrum by perpendicular magnetic-field components, leaving the remaining nanowire facets unaffected. Our results open up great opportunities for development of dissipation-less electronics and spintronics. © 2016 American Chemical Society.

  • 20.
    Hajji, Maryam
    Högskolan i Halmstad, Sektionen för Informationsvetenskap, Data– och Elektroteknik (IDE).
    A comparative study of Nanowire-based InP and Planar ITO/InP Photodetectors2011Independent thesis Advanced level (degree of Master (One Year)), 15 poäng / 22,5 hpOppgave
    Abstract [en]

    Photodetectors are a kind of semiconductor devices that convert incoming light to an electrical signal. Photodetectors have different applications in sensors and fiber optic communication systems, and medical diagnosis etc.

    In this project  Fourier Transform Infrared (FTIR) Spectroscopy is used to investigate a new version  of photodiodes for near-infrared radiation that is based on self-assembled semiconductor nanowires (NWs) which are grown directly on the substrate without any epi-layer. The spectrally resolved photocurrent (at different applied biases) and IV curves (in darkness and illumination) for different temperatures have been studied, respectively.

    The thesis work also includes a comparison to a planar photodetector based on Indium Tin Oxide (ITO) deposited directly on an InP substrate.

     

     

  • 21.
    Hussain, Laiq
    et al.
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS).
    Pettersson, Håkan
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS), Tillämpad matematik och fysik (MPE-lab).
    Wang, Q.
    Acreo Swedish ICT AB, Kista, 16425, Sweden.
    Karim, A.
    Acreo Swedish ICT AB, Kista, 16425, Sweden.
    Anderson, J.
    Acreo Swedish ICT AB, Kista, 16425, Sweden.
    Jafari, Mehrdad
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS), Tillämpad matematik och fysik (MPE-lab).
    Song, J.
    Center for Opto-Electronic Convergence Systems, Korea Institute of Science and Technology, Seoul, 02792, South Korea.
    Choi, W. J.
    Center for Opto-Electronic Convergence Systems, Korea Institute of Science and Technology, Seoul, 02792, South Korea.
    Han, I. K.
    Center for Opto-Electronic Convergence Systems, Korea Institute of Science and Technology, Seoul, 02792, South Korea.
    Lim, J. Y.
    Center for Opto-Electronic Convergence Systems, Korea Institute of Science and Technology, Seoul, 02792, South Korea.
    SWIR-LWIR Photoluminescence from Sb-based Epilayers Grown on GaAs Substrates by using MBE2018Inngår i: Journal of the Korean Physical Society, ISSN 0374-4884, E-ISSN 1976-8524, Vol. 73, nr 11, s. 1604-1611Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Utilizing Sb-based bulk epilayers on large-scale low-cost substrates such as GaAs for fabricating infrared (IR) photodetectors is presently attracting significant attention worldwide. For this study, three sample series of GaAsxSb1−x, In1−xGaxSb, and InAsxSb1−x with different compositions were grown on semi-insulating GaAs substrates by using molecular beam epitaxy (MBE) and appropriate InAs quantum dots (QDs) as a defect-reduction buffer layer. Photoluminescence (PL) signals from these samples were observed over a wide IR wavelength range from 2 ÎŒm to 12 ÎŒm in agreement with the expected bandgap, including bowing effects. In particular, interband PL signals from InAsxSb1−x and In1−xGaxSb samples even at room temperature show promising potential for IR photodetector applications. © 2018, The Author(s).

  • 22.
    Höglund, Linda
    et al.
    Acreo AB, Kista, Sweden.
    Holtz, Per-Olof
    Department of Physics, Chemistry and Biology (IFM), Linköping University, Linköping, Sweden.
    Asplund, Carl
    IRnova, Kista, Sweden.
    Wang, Qin
    Acreo AB, Kista, Sweden.
    Almqvist, Susanne
    Acreo AB, Kista, Sweden.
    Malm, Hedda
    IRnova, Kista, Sweden.
    Pettersson, Håkan
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS), Tillämpad matematik och fysik (MPE-lab).
    Andersson, Jan Yngve
    Acreo AB, Kista, Sweden.
    Dual source optical pumping experiments revealing the origin of low temperature photocurrent peaks in quantum dots-in-a-well infrared photodetectors2008Konferansepaper (Fagfellevurdert)
  • 23.
    Höglund, Linda
    et al.
    Acreo AB, Kista, Sweden & Linköping University, Linköping, Sweden.
    Holtz, Per-Olof
    Linköping University, Linköping, Sweden.
    Asplund, Carl
    IRnova, Kista, Sweden.
    Wang, Qin
    Acreo AB, Kista, Sweden.
    Almqvist, Susanne
    Acreo AB, Kista, Sweden.
    Petrini, Erik
    Acreo AB, Kista, Sweden.
    Andersson, Jan Y.
    Acreo AB, Kista, Sweden.
    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.
    Tuning of the detection wavelength in quantum dots-in-a-well infrared photodetectors2008Inngår i: Proceedings of SPIE, 6940, Infrared Technology and Applications XXXIV, 694002, 2008, Vol. 6940, nr 1-2, artikkel-id 694002Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this study, bias mediated tuning of the detection wavelength within the infrared wavelength region is demonstrated for quantum dots-in-a-well (DWELL) infrared photodetectors. In DWELL structures, intersubband transitions in the conduction band occur from a discrete state in the quantum dot to a subband inthe quantum well. Compared to "conventional" quantum dot infrared photodetectors, where the transitions take place between different discrete bands in thequantum dots, new possibilities to tune the detection wavelength window are opened up, partly by varying the quantum dot energy levels and partly by adjusting the width and composition of the quantum well. In the DWELL structure used, an asymmetric positioning of the InAs quantum dot layer in a 8 nm wide In0.15Ga0.85As/GaAs QW has been applied which enables tuning of the peak detection wavelength within the long wavelength infrared (LWIR; 8 - 14 gm) region. When the applied bias was reversed, a wavelength shift from 8.5 to 9.5 mu m was observed for the peak position in the spectral response. For another DWELL structure, with a well width of 2 nm, the tuning range of the detector could be shifted from the medium wavelength infrared (MWIR; 3-5 mu m) region to the LWIR region. With small changes in the applied bias, the peak detection wavelength could be shifted from 5.1 to 8 mu m. These tuning properties ofDWELL structures could be essential for applications such as modulators and two-colour infrared detection. © (2008) COPYRIGHT SPIE--The International Society for Optical Engineering.

  • 24.
    Höglund, Linda
    et al.
    Acreo AB, Kista, Sweden.
    Holtz, Per-Olof
    IFM, Linköping University, Linköping, Sweden.
    Asplund, Carl
    IRnova AB, Kista, Sweden.
    Wang, Qin
    Acreo AB, Kista, Sweden.
    Almqvist, Susanne
    Acreo AB, Kista, Sweden.
    Petrini, Erik
    Acreo AB, Kista, Sweden.
    Pettersson, Håkan
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS), Tillämpad matematik och fysik (MPE-lab).
    Andersson, Jan Y.
    Acreo AB, Kista, Sweden.
    Voltage mediated tuning of the detection wavelength in quantum dots-in-a-well infrared photodetectors2008Konferansepaper (Fagfellevurdert)
  • 25.
    Höglund, Linda
    et al.
    Industrial Nano- and Microtechnology, Acreo AB, Kista, Sweden.
    Holtz, Per-Olof
    Department of Physics, Chemistry and Biology (LFM), Linköping University, Linköping, Sweden.
    Ouattara, L.
    Synchrotron Radiation Research, Lund University, Lund, Sweden.
    Asplund, Carl
    IRnova, Kista, Sweden.
    Wang, Qin
    Industrial Nano- and Microtechnology, Acreo AB, Kista, Sweden.
    Almqvist, Susanne
    Industrial Nano- and Microtechnology, Acreo AB, Kista, Sweden.
    Petrini, Erik
    Industrial Nano- and Microtechnology, Acreo AB, Kista, Sweden.
    Malm, Hedda
    IRnova, Kista, Sweden.
    Borglind, J.
    Industrial Nano- and Microtechnology, Acreo AB, Kista, Sweden.
    Smuk, S.
    Industrial Nano- and Microtechnology, Acreo AB, Kista, Sweden.
    Mikkelsen, A.
    Synchrotron Radiation Research, Lund University, Lund, Sweden.
    Lundgren, E.
    Synchrotron Radiation Research, 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 the Nanometer Consortium, Lund University, Lund, Sweden.
    Andersson, Jan Y.
    Industrial Nano- and Microtechnology, Acreo AB, Kista, Sweden.
    Quantum dots-in-a-well infrared photodetectors for long wavelength infrared detection2006Inngår i: Proceedings of SPIE: The International Society for Optical Engineering / [ed] James G. Grate, Francois Kajzar & Mikael lindgren, Bellingham, Wash.: SPIE - International Society for Optical Engineering, 2006, s. U51-U63Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We report on a quantum dots-in-a-well infrared photodetector (DWELL QDIP) grown by metal organic vapor phase epitaxy. The DWELL QDIP consisted of ten stacked InAs/In0.5Ga0.85As/GaAs QD layers embedded between n-doped contact layers. The density of the QDs was about 9 × 10 10 cm-2 per QD layer. The energy level structure of the DWELL was revealed by optical measurements of interband transitions, and from a comparison with this energy level scheme the origin of the photocurrent peaks could be identified. The main intersubband transition contributing to the photocurrent was associated with the quantum dot ground state to the quantum well excited state transition. The performance of the DWELL QDIPs was evaluated regarding responsivity and dark current for temperatures between 15 K and 77 K. The photocurrent spectrum was dominated by a LWIR peak, with a peak wavelength at 8.4 μm and a full width at half maximum (FWHM) of 1.1 μm. At an operating temperature of 65 K, the peak responsivity was 30 mA/W at an applied bias of 4 V and the dark current was 1.2×10-5 A/cm2. Wavelength tuning from 8.4 μm to 9.5 μm was demonstrated, by reversing the bias of the detector.

  • 26.
    Höglund, Linda
    et al.
    Acreo AB.
    Karlsson, Fredrik
    IFM, Linköping University.
    Holtz, Per-Olof
    IFM, Linköping University.
    Pettersson, Håkan
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS), Tillämpad matematik och fysik (MPE-lab).
    Pistol, Mats-Erik
    Avd. f. Fasta Tillståndets Fysik, Lunds Universitet.
    Wang, Qin
    Acreo AB.
    Almqvist, Susanne
    Acreo AB.
    Asplund, Carl
    IRnova.
    Malm, Hedda
    IRnova.
    Petrini, Erik
    Acreo AB.
    Andersson, Jan
    Acreo AB.
    Energy level scheme of InAs/InxGa1-xAs/GaAs quantum-dots-in-a-well infrared photodetector structures2010Inngår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 82, nr 3, s. 035314-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A thorough investigation of quantum-dots-in-a-well structures for infrared photodetector applications has been performed employing different experimental techniques. The electronic structure of self-assembled InAs quantum dots embedded in an In0.15Ga0.85As/GaAs quantum well (QW) was deduced from photoluminescence (PL) and PL excitation (PLE) spectroscopy. From polarization-dependent PL it was revealed that the quantum dots hold two electron energy levels and two heavy-hole levels. Tunnel capacitance spectroscopy confirmed an electron energy level separation of about 50 meV, and additionally, that the conduction-band ground state and excited state of the dots are twofold and fourfold degenerates, respectively. Intersubband photocurrent spectroscopy, combined with simultaneous interband pumping of the dots, revealed a dominant transition at 150 meV (8.5 mu m) between the ground state of the quantum dots and the excited state of the QW. Results from detailed full three-dimensional calculations of the electronic structure, including effects of composition intermixing and interdot interactions, confirm the experimentally unravelled energy level scheme of the dots and well.

  • 27.
    Iakovleva, Natalia
    et al.
    Petrozavodsk State University, Russia.
    Kokatev, Alexander
    Petrozavodsk State University.
    Pettersson, Håkan
    Petrozavodsk State University, Russia.
    Savchenko, O.
    Petrozavodsk State University, Russia.
    Iakovlev, A.
    Petrozavodsk State University, Russia.
    Chupakhina, E.
    Petrozavodsk State University, Russia.
    Suomolajnen, K.
    Petrozavodsk State University, Russia.
    Stepanova, K.
    Petrozavodsk State University, Russia.
    Khanina, E.
    Petrozavodsk State University, Russia.
    Self-organized porous anodic oxide matrix and nanocomposite materials on their base2011Konferansepaper (Fagfellevurdert)
  • 28.
    Jafari Jam, Reza
    Lund University, Lund, Sweden.
    Gold Electrodeposition in Semiconductor Nanowire Technology2017Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Semiconductor nanowires are widely considered as promising candidates for next generations of electronics and optoelectronics. Gold seed particles have so far been recognized as the most important catalyst for growth of nanowires. Costs related to substrates, lithography processes and gold consumption most strongly influence the final cost of nanowire-based devices. An optimum gold deposition process can facilitate re-use of substrates, avoid repetitive lithogra-phy processes and reduce the gold consumption in order to reduce the cost of the final device. In this work, we report on nanowire seed definition by gold electrodeposition. Electron microscopy inspection and optical spectroscopy confirm that the subsequently grown III-V nanowires have surface morphology and crystal quality comparable to those of nanowires grown from seed particles defined by conventional thermal evaporation. For seeding of substrates used in a typical growth run, we used around 650 times less gold with a 10 times higher throughput as compared to thermal evaporation. Using selective gold electrodeposition, we demonstrated redeposition of seed particles on a substrate after nanowire peel-off in order to reuse it for multiple growth runs. We also demonstrated the possibility of depositing seed particles in deep holes etched in thick masks to facilitate template-assisted growth of nanowires on (001) substrates.

  • 29.
    Jafari Jam, Reza
    et al.
    Division of Solid State Physics/Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Heurlin, Magnus
    Division of Solid State Physics/Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Jain, Vishal
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS). Division of Solid State Physics/Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Kvennefors, Anders
    Division of Solid State Physics/Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Graczyk, Mariusz
    Division of Solid State Physics/Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Maximov, Ivan
    Division of Solid State Physics/Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Borgström, Magnus T.
    Division of Solid State Physics/Nanometer Structure Consortium, 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). Division of Solid State Physics/Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Samuelson, Lars
    Division of Solid State Physics/Nanometer Structure Consortium, Lund University, Lund, Sweden.
    III-V nanowire synthesis by use of electrodeposited gold particles2015Inngår i: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 15, nr 1, s. 134-138Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Semiconductor nanowires are great candidates for building novel electronic devices. Considering the cost of fabricating such devices, substrate reuse and gold consumption are the main concerns. Here we report on implementation of high throughput gold electrodeposition for selective deposition of metal seed particles in arrays defined by lithography for nanowire synthesis. By use of this method, a reduction in gold consumption by a factor of at least 300 was achieved, as compared to conventional thermal evaporation for the same pattern. Because this method also facilitates substrate reuse, a significantly reduced cost of the final device is expected. We investigate the morphology, crystallography, and optical properties of InP and GaAs nanowires grown from electrodeposited gold seed particles and compare them with the properties of nanowires grown from seed particles defined by thermal evaporation of gold. We find that nanowire synthesis, as well as the material properties of the grown nanowires are comparable and quite independent of the gold deposition technique. On the basis of these results, electrodeposition is proposed as a key technology for large-scale fabrication of nanowire-based devices.

  • 30.
    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 NanoLund, Lund University, Lund, Sweden.
    Heurlin, Magnus
    Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Barrigon, Enrique
    Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Bosco, Lorenzo
    Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Nowzari, Ali
    Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Schroff, Shishi
    Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Boix, Virginia
    Solid State Physics and NanoLund, 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 NanoLund, Lund University, Lund, Sweden.
    Jafari Jam, Reza
    Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Berg, Alexander
    Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Samuelson, Lars
    Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Borgström, Magnus T.
    Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Capasso, Federico
    School of Engineering and Applied Sciences, Harvard University, Cambridge, United States.
    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 NanoLund, Lund University, Lund, Sweden.
    InP/InAsP Nanowire-Based Spatially Separate Absorption and Multiplication Avalanche Photodetectors2017Inngår i: ACS Photonics, E-ISSN 2330-4022, Vol. 4, nr 11, s. 2693-2698Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Avalanche photodetectors (APDs) are key components in optical communication systems due to their increased photocurrent gain and short response time as compared to conventional photodetectors. A detector design where the multiplication region is implemented in a large band gap material is desired to avoid detrimental Zener tunneling leakage currents, a concern otherwise in smaller band gap materials required for absorption at 1.3/1.55 μm. Self-assembled III-V semiconductor nanowires offer key advantages such as enhanced absorption due to optical resonance effects, strain-relaxed heterostructures, and compatibility with mainstream silicon technology. Here, we present electrical and optical characteristics of single InP and InP/InAsP nanowire APD structures. Temperature-dependent breakdown characteristics of p+-n-n+ InP nanowire devices were investigated first. A clear trap-induced shift in breakdown voltage was inferred from I-V measurements. An improved contact formation to the p+-InP segment was observed upon annealing, and its effect on breakdown characteristics was investigated. The band gap in the absorption region was subsequently varied from pure InP to InAsP to realize spatially separate absorption and multiplication APDs in heterostructure nanowires. In contrast to the homojunction APDs, no trap-induced shifts were observed for the heterostructure APDs. A gain of 12 was demonstrated for selective optical excitation of the InAsP segment. Additional electron-beam-induced current measurements were carried out to investigate the effect of local excitation along the nanowire on the I-V characteristics. Simulated band profiles and electric field distributions support our interpretation of the experiments. Our results provide important insight for optimization of avalanche photodetector devices based on III-V nanowires. © 2017 American Chemical Society

  • 31.
    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.  

  • 32.
    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 the Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Heurlin, Magnus
    Solid State Physics and the Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Lindgren, David
    Solid State Physics and the Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Nowzari, Ali
    Solid State Physics and the Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Hussein, Laiq
    Solid State Physics and the Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Wallentin, Jesper
    Solid State Physics and the Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Capasso, Federico
    School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, USA.
    Borgström, Magnus T.
    Solid State Physics and the Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Gustafsson, Anders
    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.
    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 the Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Large area photodetectors based on InP NWs with InAs/InAsP QWs2014Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Focal plane arrays have a widespread use in infrared imaging, which often rely on cryogenic cooling to curtail the dark current level necessary for a reasonable signal-to-noise ratio. Quantum well (QW) infrared photodetectors are uniform over large areas, but suffer from a severe drawback related to the selection rules for intersubband absorption. An interesting alternative is self-assembled III-V nanowires offering a key advantage owing to the enhanced absorption by optical resonance effects and strain relaxation.We present electrical and optical results from large ensembles of n+-i-n+ InP NWs, axially grown on InP substrates with InAs/InAsP QWs embedded within the i-segment, designed for both interband and intersubband detection. The NWs are contacted in a vertical geometry using 50 nm SiO2 as the insulating layer and ITO as the top contact. We first investigate the crystal quality of the InAsP QWs grown in 180 nm diameter NWs, using PL, CL and TEM. To achieve more abrupt InAs/InAsP QWs, we grow 130 nm diameter NWs and deplete the In present in the Au catalysts. The effect of n-doping on the device performance is studied by fabricating two different NW geometries, with and without an n+-segment grown before the nominal i-segment in the NW. In addition, the position of the QWs within the i-segment is varied to further scrutinize effects related to doping and crystal structure. Finally, we report spectrally resolved photocurrent results from the QWs in the near-infrared region and discuss about the further developments needed for intersubband detection.

  • 33.
    Jain, Vishal
    et al.
    Solid State Physics and the Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Heurlin, Magnus
    Solid State Physics and the Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Nowzari, Ali
    Solid State Physics and the Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Lindgren, David
    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.
    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.
    Pettersson, Håkan
    Solid State Physics and the Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Large Area Photodetectors at 1.3/1.55 μm Based on InP/InAsP NWs2014Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Optical communication systems benefit a lot from APDs due to their increased photocurrent gain as compared to conventional photodetectors. An avalanche region in a high bandgap material is especially useful to avoid the tunneling leakage currents in smaller bandgap materials needed for absorption at 1.3/1.55 µm wavelengths. Self-assembled III-V semiconductor nanowires have a key advantage owing to the enhanced absorption due to optical resonance effects and the strain relaxation in NWs, thus facilitating monolithic integration of different heterostructures on cheaper substrates. Here, we present electrical and optical results from large ensembles of InP/InAsP NWs, axially grown on p+ InP substrates. The NW base consists of an InP p-n junction acting as the avalanche region followed by an InP/InAsP absorption region, and ending with a top InP n+-segment. The 130nm diameter NW arrays are contacted in a vertical geometry using SiO2 as the insulating layer and ITO as the top contact. The n-doping in the avalanche region is varied to study it’s influence on the avalanche mechanism. Also the bandgap in the absorption region is varied from pure InP to smaller bandgap InAsP by varying the As content. Clear interband signals from different crystal phases of InP/InAsP are observed in photocurrent spectroscopy. Moreover, the photocurrent spectra are consistent with spatially resolved photoluminescence signals. We also report on polarization and angle dependent photocurrent response of the NW array.

  • 34.
    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 the Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Wallentin, Jesper
    Solid State Physics and the Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Nowzari, Ali
    Solid State Physics and the Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Heurlin, Magnus
    Solid State Physics and the Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Asoli, Damir
    Sol Voltaics AB, Lund, Sweden.
    Borgström, Magnus T.
    Solid State Physics and the Nanometer Structure Consortium, Lund University, 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.
    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 the Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Processing and Characterization of Nanowire Arrays for Photodetectors2015Inngår i: Nano-Structures for Optics and Photonics: Optical Strategies for Enhancing Sensing, Imaging, Communication and Energy Conversion / [ed] Baldassare Di Bartolo, John Collins & Luciano Silvestri, Dordrecht: Springer, 2015, s. 511-512Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We present a fabrication scheme of contacting arrays of vertically standing nanowires (NW) for LEDs (Duan et al. Nature 409:66–69, 2001), photodetectors (Wang et al. Science (NY) 293:1455–1457, 2001) or solar cell applications (Wallentin et al. Science (NY) 339:1057–1060, 2013). Samples were prepared by depositing Au films using nano-imprint lithography (Må rtensson et al. Nano Lett 4:699–702, 2004) which are used as catalysts for NW growth in a low-pressure metal organic vapour phase epitaxy system where III-V precursors and dopant gases are flown at elevated temperatures which lead to the formation of NWs with different segments (Borgström et al. Nano Res 3:264–270, 2010). An insulating SiO2 layer is then deposited and etched from the top segments of the NWs followed by sputtering of a transparent top conducting oxide and opening up 1 × 1 mm2 device areas through a UV lithography step and etching of the top contact from non-device areas. A second UV lithography step was subsequently carried out to open up smaller windows on the ITO squares for bond pad definition, followed by metallization and lift-off; and the substrate is used as back contact. We also report on the electrical and optical properties of near-infrared p+−i−n+ photodetectors/solar cells based on square millimeter ensembles of InP nanowires grown on InP substrates. The study includes a sample series where the p +-segment length was varied between 0 and 250 nm, as well as solar cell samples with 9.3 % efficiency with similar design. The NWs have a complex modulated crystal structure of alternating wurtzite and zincblende segments, a polytypism that depends on dopant type. The electrical data for all samples display excellent rectifying behavior with an ideality factor of about 2 at 300 K. From spectrally resolved photocurrent measurements, we conclude that the photocurrent generation process depends strongly on the p +-segment length. Without p +-segment in the NWs, photogenerated carriers funneled from the substrate into the NWs contribute significantly to the photocurrent. Adding a p +-segment shifts the depletion region up into the i-region of the NWs reducing the substrate contribution to photocurrent while strongly improving the collections of carriers generated in the NWs, in agreement with theoretical modeling (Fig. 48.1). © Springer Science+Business Media Dordrecht 2015.

  • 35.
    Janousch, Markus
    et al.
    Swiss Light Source, Paul Scherrer Institut, Villigen, Switzerland.
    Meijer, G. Ingmar
    IBM Research, Zurich Research Laboratory, Rüschlikon, Switzerland.
    Staub, Urs
    Swiss Light Source, Paul Scherrer Institut, Villigen, Switzerland.
    Delley, Bernard
    Swiss Light Source, Paul Scherrer Institut, Villigen, Switzerland.
    Karg, Siegfried F.
    IBM Research, Zurich Research Laboratory, Rüschlikon, Switzerland.
    Andreasson, Björn Pererik
    Swiss Light Source, Paul Scherrer Institut, Villigen, Switzerland.
    Role of oxygen vacancies in cr-doped SrTiO3 for resistance-change memory2007Inngår i: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 19, nr 17, s. 2232-2235Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A high density of oxygen vacancies has been found in an experiment to determine the path of electrical conduction in Cr-doped SrTiO3 memory cells. The Cr acts as a seed for the localization of oxygen vacancies, leading to a statistically homogeneous distribution of charge carriers within the path. This warrants a controllable doping profile and improved device scaling down to the nanometer scale. The combination of laterally resolved micro-X-ray absorption spectroscopy and thermal imaging concludes that the resistance switching in Cr-doped SrTiO3 originates from an oxygen-vacancy drift to/from the electrode that was used as anode during the conditioning process. The experiments shows that this oxygen vacancy concept is crucial for the entire class of transition-metal-oxide-based bipolar resistance-change memory.

  • 36.
    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
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS). Solid State Physics/The Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Kumar, Sandeep
    Högskolan i Halmstad, Akademin för informationsteknologi, 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
    Högskolan i Halmstad, Akademin för informationsteknologi, 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)2015Inngår i: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 48, nr 7, artikkel-id 079501Artikkel i tidsskrift (Fagfellevurdert)
  • 37.
    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
    Högskolan i Halmstad, Akademin för informationsteknologi. Solid State Physics/The Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Kumar, Sandeep
    Högskolan i Halmstad, Akademin för informationsteknologi. 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
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS), Tillämpad matematik och fysik (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 nanowires2014Inngår i: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 47, nr 39, artikkel-id 394003Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 38.
    Jorlöv, Sofia
    et al.
    Högskolan i Halmstad, Sektionen för ekonomi och teknik (SET), Bio- och miljösystemforskning (BLESS), Biomekanik och biomedicin.
    Hammarström, Jessica
    Högskolan i Halmstad, Sektionen för ekonomi och teknik (SET), Bio- och miljösystemforskning (BLESS), Biomekanik och biomedicin.
    Comparison Study of the Two Pediatric ATDs: Hybrid III 6-Year-Old and Q62011Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    As a new pediatric dummy family, the Q-family, is suggested for the European childsafety regulations (R44) and the updated EuroNCAP, it needed to be tested andcompared to the older pediatric dummy family, Hybrid III, used in testing at Autolivtoday.In this study, tests were performed with the Q6 and the Hybrid III 6-year-old. Bothdummies were subjected to eight sled tests using a EuroNCAP acceleration pulse. The sled represented the interior of a Volvo V70, with integrated booster cushions mounted onto the car body through a rigid fixture. Standard belt were used for all tests, except one where pretensioning was used. Static tests investigated how the chest deflection on Q6 was affected by the shoulder belt geometry. Large difference in belt interaction was observed between the dummies. The beltslipped off the Hybrid III’s shoulder for all tests except one, while the belt on the Qdummy’swas hard to provoke off the shoulder. The overall kinematic behavior, beforethe belt slipped off the Hybrid III’s shoulder, were similar for both dummies. Differences in chest deflection on the Q6, depending on the belt geometry, were observed in both the dynamic and the static tests; a shoulder belt geometry closer to theneck resulted in minor displacement than a mid-shoulder belt geometry. After testing, five different damages were observed on the Q6.

  • 39.
    Jurgilaitis, A.
    et al.
    Department of Physics & MAX IV Laboratory, Lund University, Lund, Sweden.
    Enquist, H.
    MAX IV Laboratory, Lund University, Lund, Sweden.
    Andreasson, Björn Pererik
    Department of Physics, Lund University, Lund, Sweden.
    Persson, A. I. H.
    Department of Physics, Lund University, Lund, Sweden.
    Borg, B. M.
    Department of Electrical and Information Technology, Lund University, Lund, Sweden.
    Caroff, P.
    Department of Electronic Materials Engineering, Research School of Physics and Engineering, The Australian National University, Canberra, Australia.
    Dick, K. A.
    Department of Physics, Lund University, Lund, Sweden & Division of Polymer and Materials Chemistry, Department of Chemistry, Lund University, Lund, Sweden.
    Harb, M.
    Department of Physics & MAX IV Laboratory, Lund University, Lund, Sweden.
    Linke, H.
    Department of Physics, Lund University, Lund, Sweden.
    Nüske, R.
    Department of Physics, Lund University, Lund, Sweden.
    Wernersson, L.-E.
    Department of Electrical and Information Technology, Lund University, Lund, Sweden.
    Larsson, J.
    Department of Physics, Lund University, Lund, Sweden.
    Time-Resolved X-ray Diffraction Investigation of the Modified Phonon Dispersion in InSb Nanowires2014Inngår i: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 14, nr 2, s. 541-546Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The modified phonon dispersion is of importance for understanding the origin of the reduced heat conductivity in nanowires. We have measured the phonon dispersion for 50 nm diameter InSb (111) nanowires using time-resolved X-ray diffraction. By comparing the sound speed of the bulk (3880 m/s) and that of a classical thin rod (3600 m/s) to our measurement (2880 m/s), we conclude that the origin of the reduced sound speed and thereby to the reduced heat conductivity is that the C44 elastic constant is reduced by 35% compared to the bulk material. © 2014 American Chemical Society.

  • 40.
    Karimi, Mohammad
    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 NanoLund, Lund University, Lund, Sweden.
    Heurlin, Magnus
    Solid State Physics and NanoLund, Lund University, Lund, Sweden & Sol Voltaics AB, Lund, Sweden.
    Limpert, Steven
    Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Jain, Vishal
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS), Tillämpad matematik och fysik (MPE-lab). Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Zeng, Xulu
    Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Geijselaers, Irene
    Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Nowzari, Ali
    Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Fu, Ying
    Department of Applied Physics, Royal Institute of Technology (KTH), Solna, Sweden.
    Samuelson, Lars
    Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Linke, Heiner
    Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Borgström, Magnus T.
    Solid State Physics and NanoLund, 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 NanoLund, Lund University, Lund, Sweden.
    Intersubband Quantum Disc-in-Nanowire Photodetectors with Normal-Incidence Response in the Long-Wavelength Infrared2018Inngår i: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 18, nr 1, s. 365-372Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Semiconductor nanowires have great potential for realizing broadband photodetectors monolithically integrated with silicon. However, the spectral range of such detectors has so far been limited to selected regions in the ultraviolet, visible and near-infrared. Here, we report on the first intersubband nanowire heterostructure array photodetectors exhibiting a spectrally resolved photoresponse from the visible to long-wavelength infrared. In particular, the infrared response from 3-20 mm is enabled by intersubband transitions in low-bandgap InAsP quantum discs synthesized axially within InP nanowires. The intriguing optical characteristics, including unexpected sensitivity to normal incident radiation, are explained by excitation of the longitudinal component of optical modes in the photonic crystal formed by the nanostructured portion of the detectors. Our results provide a generalizable insight into how broadband nanowire photodetectors may be designed, and how engineered nanowire heterostructures open up new fascinating opportunities for optoelectronics.

  • 41.
    Karimi, Mohammad
    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 NanoLund, Lund University, Lund, Sweden.
    Jain, Vishal
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS), Tillämpad matematik och fysik (MPE-lab). Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Heurlin, Magnus
    Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Nowzari, Ali
    Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Hussain, Laiq
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS). Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Lindgren, David
    Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Stehr, Jan Eric
    Department of Physics, Chemistry and Biology, Linköping University, Linköping, Sweden.
    Buyanova, Irina A.
    Department of Physics, Chemistry and Biology, Linköping University, Linköping, Sweden.
    Gustafsson, Anders
    Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Samuelson, Lars
    Solid State Physics and NanoLund, Lund University, Lund, Sweden.
    Borgström, Magnus T.
    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.
    Room-temperature InP/InAsP Quantum Discs-in-Nanowire Infrared Photodetectors2017Inngår i: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 17, nr 6, s. 3356-3362Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The possibility to engineer nanowire heterostructures with large bandgap variations is particularly interesting for technologically important broadband photodetector applications. Here we report on a combined study of design, fabrication, and optoelectronic properties of infrared photodetectors comprising four million n+–i–n+ InP nanowires periodically ordered in arrays. The nanowires were grown by metal–organic vapor phase epitaxy on InP substrates, with either a single or 20 InAsP quantum discs embedded in the i-segment. By Zn compensation of the residual n-dopants in the i-segment, the room-temperature dark current is strongly suppressed to a level of pA/NW at 1 V bias. The low dark current is manifested in the spectrally resolved photocurrent measurements, which reveal strong photocurrent contributions from the InAsP quantum discs at room temperature with a threshold wavelength of about 2.0 μm and a bias-tunable responsivity reaching 7 A/W@1.38 μm at 2 V bias. Two different processing schemes were implemented to study the effects of radial self-gating in the nanowires induced by the nanowire/SiOx/ITO wrap-gate geometry. Summarized, our results show that properly designed axial InP/InAsP nanowire heterostructures are promising candidates for broadband photodetectors. © 2017 American Chemical Society.

  • 42.
    Karthik, K. R. G.
    et al.
    School of Materials Science and Engineering, Nanyang Technological University, Singapore, Singapore.
    Andreasson, Björn Pererik
    School of Materials Science and Engineering, Nanyang Technological University, Singapore, Singapore.
    Sun, C.
    School of Materials Science and Engineering, Nanyang Technological University, Singapore, Singapore.
    Pramana, S. S.
    School of Materials Science and Engineering, Nanyang Technological University, Singapore, Singapore.
    Varghese, B.
    Department of Physics, National University of Singapore, Singapore, Singapore.
    Sow, C. H.
    Department of Physics, National University of Singapore, Singapore, Singapore.
    Mathews, N.
    School of Materials Science and Engineering, Nanyang Technological University, Singapore, Singapore.
    Wong, L. H.
    School of Materials Science and Engineering, Nanyang Technological University, Singapore, Singapore.
    Mhaisalkar, S. G.
    School of Materials Science and Engineering, Nanyang Technological University, Singapore, Singapore.
    Physical and Electrical Properties of Single Zn2SnO4 Nanowires2011Inngår i: Electrochemical and solid-state letters, ISSN 1099-0062, E-ISSN 1944-8775, Vol. 14, nr 1, s. K5-K7Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Electrical characterizations of single Zn2SnO4 (ZTO) nanowire devices are presented. These include resistivity, mobility, and photosensing measurements. The resistivity and the mobility of the Zn2SnO4 nanowire were measured to be 5.6 cm and 0.2 cm2/Vs, respectively. These values were found to be strongly dependent on the amount of electron-donating defects and less dependent on the thickness of the nanowires. An increase in the resistivity when changing the ambient atmosphere is observed. This change is caused by defect states lying in the bandgap, as shown by photoluminescence. The results imply the potential of ZTO nanowires as phototransistors and other photosensitive devices. © 2010 The Electrochemical Society.

  • 43.
    Kuiper, Peter
    et al.
    Högskolan i Halmstad. Department of Physics, Uppsala University, Uppsala, Sweden.
    van Elp, J.
    ISA, Institute of Physics and Astronomy, University of Aarhus, Aarhus, Denmark.
    Rice, D. E
    Buttrey, D. J
    Lin, H.-J
    Chen, C. T
    Polarization-dependent nickel 2p x-ray-absorption spectra La2NiO4+δ1998Inngår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 57, nr 3, s. 1552-1557Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present polarization dependent x-ray-absorption spectra at nickel (Formula presented) edges of well-characterized (Formula presented) single crystals. In the stoichiometric compound the splitting between the (Formula presented) and the (Formula presented) orbitals is 0.7 eV, according to a fit of the (Formula presented) multiplet to the spectra. This value is in agreement with an assignment of (Formula presented) excitations of the optical spectrum. The Ni (Formula presented) edges of the doped compound are consistent with the isotropic prepeak observed at the oxygen (Formula presented) edge. Theory does not predict holes on the apex oxygens, but we argue that doping causes a polaronic deformation which reduces the tetragonal distortion of the NiO(Formula presented) octahedra, and delocalizes the hole over all six ligands. © 1998 The American Physical Society.

  • 44.
    Kuiper, Pieter
    et al.
    Högskolan i Halmstad, Akademin för ekonomi, teknik och naturvetenskap. Department of Physics, Uppsala University, Uppsala, Sweden.
    Guo, Jinghua
    Department of Physics, Uppsala University, Uppsala, Sweden.
    Såthe, Conny
    Department of Physics, Uppsala University, Uppsala, Sweden.
    Duda, Laurent Claudius
    Department of Physics, Uppsala University, Uppsala, Sweden & Department of Physics, Boston University, Boston, USA.
    Nordgren, Joseph
    Department of Physics, Uppsala University, Uppsala, Sweden.
    Pothuizen, J. J. M.
    Laboratory of Solid State Physics, Materials Science Center, University of Groningen, Groningen, Netherlands.
    De Groot, Frank M. F.
    Laboratory of Solid State Physics, Materials Science Center, University of Groningen, Groningen, Netherlands.
    Sawatzky, George Albert
    Laboratory of Solid State Physics, Materials Science Center, University of Groningen, Groningen, Netherlands.
    Resonant X-Ray raman spectra of Cu dd excitations in Sr2CuO2Cl21998Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 80, nr 23, s. 5204-5207Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present resonant x-ray Raman scattering results on Sr2CuO2Cl2, a model compound for high- Tc superconductors. We demonstrate that the dd excitations can be observed and show that the polarization dependence can be used to identify the dd excitations. We find the transition from the dx2−y2 ground state to the dxy excited state at 1.35 eV and to the degenerate dxz and dyz excited states at 1.7 eV. From analysis of the polarization dependence we conclude that the d3z2−r2 orbital energy is at 1.5 eV and not in the midinfrared (0.5 eV) as recently suggested. We use recent theoretical arguments to show that the d3z2−r2 excitation is accompanied by a local spin flip resulting in a shift upwards of 0.2 eV due to the exchange interaction with the neighboring spins. ©1998 American Physical Society.

  • 45.
    Liu, Ruisheng
    et al.
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS), Tillämpad matematik och fysik (MPE-lab). Lund University, Lund, Sweden.
    Michalak, Lukasz
    Linnaeus University, Kalmar, Sweden.
    Canali, Carlo
    Linnaeus University, Kalmar, Sweden.
    Samuelson, Lars
    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).
    Tunneling Anisotropic Magnetoresistance in Co/AlOx /Au Tunnel Junctions2008Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We observe spin-valve-like effects in nano-scaled thermally evaporated Co/AlOx/Au tunnel junctions. The tunneling magnetoresistance is anisotropic and depends on the relative orientation of the magnetization direction of the Co electrode with respect to the current direction. We attribute this effect to a two-step magnetization reversal and an anisotropic density of states resulting from spin-orbit interaction. The results of this study points to future applications of novel spintronics devices involving only one ferromagnetic layer.

  • 46.
    Liu, Ruisheng
    et al.
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS), Tillämpad matematik och fysik (MPE-lab).
    Pettersson, Håkan
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS), Tillämpad matematik och fysik (MPE-lab).
    Michalak, Lukasz
    Högskolan i Kalmar, Kalmar, Sweden.
    Canali, C. M.
    Linné Universitetet, Kalmar, Sweden.
    Samuelson, Lars
    Avd. f. Fasta Tillståndets Fysik, Lunds Universitet.
    Ferromagnetic single-electron transistors fabricated by atomic force microscopy2006Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We report on the fabrication and magneto-transport measurements of Ni/Au/Ni ferromagnetic single-electron transistors (F-SETs), fabricated by atomic force microscopy. By positioning a single Au disc (30 nm in diameter) into the gap between the Ni drain and source electrodes (of width 220 nm and 80 nm, respectively) step-by-step with Angstrom precision, and using plasma-processed NiOx as tunneling barriers, we can successfully fabricate F-SETs of high quality and substantial stability. The characteristic time interval of the device between two successive tunneling events is 10ps. The absence of any clear features in the transport related to the applied external magnetic field indicates that no spin-accumulation is maintained in the central Au disc. This interesting result indicates that the spin-relaxation time inside the central island should be shorter than 10ps. Based on these findings, we will discuss possible mechanisms of spin-relaxation in metal nano-structures triggered by spin-orbit interaction.

  • 47.
    Mathews, Nripan
    et al.
    School of Materials Science and Engineering, Nanyang Technological University, Singapore, Singapore.
    Varghese, Binni
    Department of Physics, National University of Singapore, Singapore, Singapore.
    Sun, Cheng
    School of Materials Science and Engineering, Nanyang Technological University, Singapore, Singapore.
    Thavasi, Velmurugan
    NUS Nanoscience and Nanotechnology Initiative, Faculty of Engineering, National University of Singapore, Singapore, Singapore.
    Andreasson, Björn Pererik
    School of Materials Science and Engineering, Nanyang Technological University, Singapore, Singapore.
    Sow, Chornghaur H.
    Department of Physics, National University of Singapore, Singapore, Singapore.
    Ramakrishna, Seeram
    Department of Physics, National University of Singapore, Singapore, Singapore & King Saud University, Riyadh, Saudi Arabia.
    Mhaisalkar, Subodh G.
    School of Materials Science and Engineering, Nanyang Technological University, Singapore, Singapore.
    Oxide nanowire networks and their electronic and optoelectronic characteristics2010Inngår i: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 2, nr 10, s. 1984-1998Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Oxide nanowire networks or oxide nanonets leverage some of the exceptional functionalities of one-dimensional nanomaterials along with the fault tolerance and flexibility of interconnected nanowires to creating exciting opportunities in large-area electronics as well as green energy systems. This paper reviews the electronic and optoelectronic properties of these networks and highlights their potential applications in field-effect transistors, optoelectronic devices, and solar cells. Techniques to grow nanowires and their subsequent integration into networks using contact printing and electrospinning are described. Electrical properties of field-effect transistors fabricated from contact printed nanowire networks are discussed, and means of integration of the nanowire networks of heterogenous materials that enable ambipolar device operation are outlined. Photocurrent properties of these nanowires are described, including the dye sensitization of large-bandgap SnO2 nanowires. The final section deals with the advantages of employing nanowire networks in dye-sensitized solar cells and the dependence of solar cell performance on morphology and surface area. © The Royal Society of Chemistry 2010.

  • 48.
    Nowzari, Ali
    et al.
    Division of Solid State Physics and The Nanometer Structure Consortium, Lund University, Sweden.
    Heurlin, Magnus
    Division of Solid State Physics and The Nanometer Structure Consortium, Lund University, Sweden.
    jain, Vishal
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS), Tillämpad matematik och fysik (MPE-lab). Division of Solid State Physics and The Nanometer Structure Consortium, Lund University, Sweden.
    Storm, Kristian
    Division of Solid State Physics and The Nanometer Structure Consortium, Lund University, Sweden.
    Hosseinnia, Ali
    Division of Solid State Physics and The Nanometer Structure Consortium, Lund University, Sweden.
    Anttu, Nicklas
    Division of Solid State Physics and The Nanometer Structure Consortium, Lund University, Sweden.
    Borgström, Magnus T.
    Division of Solid State Physics and The Nanometer Structure Consortium, Lund University, Sweden.
    Pettersson, Håkan
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS), Tillämpad matematik och fysik (MPE-lab). Division of Solid State Physics and The Nanometer Structure Consortium, Lund University, Sweden.
    Samuelson, Lars
    Division of Solid State Physics and The Nanometer Structure Consortium, Lund University, Sweden.
    A Comparative Study of Absorption in Vertically and Laterally Oriented InP Core–Shell Nanowire Photovoltaic Devices2015Inngår i: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 15, nr 3, s. 1809-1814Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have compared the absorption in InP core-shell nanowire p-i-n junctions in lateral and vertical orientation. Arrays of vertical core-shell nanowires with 400 nm pitch and 280 nm diameter, as well as corresponding lateral single core-shell nanowires, were configured as photovoltaic devices. The photovoltaic characteristics of the samples, measured under 1 sun illumination, showed a higher absorption in lateral single nanowires compared to that in individual vertical nanowires, arranged in arrays with 400 nm pitch. Electromagnetic modeling of the structures confirmed the experimental observations and showed that the absorption in a vertical nanowire in an array depends strongly on the array pitch. The modeling demonstrated that, depending on the array pitch, absorption in a vertical nanowire can be lower or higher than that in a lateral nanowire with equal absorption predicted at a pitch of 510 nm for our nanowire geometry. The technology described in this Letter facilitates quantitative comparison of absorption in laterally and vertically oriented core-shell nanowire p-i-n junctions and can aid in the design, optimization, and performance evaluation of nanowire-based core-shell photovoltaic devices. © 2014 American Chemical Society.

  • 49.
    Park, Min-Su
    et al.
    Center for Optoelectronic Convergence Systems, KIST (Korean Institute of Science and Technology), Seoul, Republic of Korea.
    Jain, Vishal
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS), Tillämpad matematik och fysik (MPE-lab). Lund Univ, Solid State Phys & Nanometer Struct Consortium, Lund, Sweden.
    Lee, E.H.
    Center for Optoelectronic Convergence Systems, KIST (Korean Institute of Science and Technology), Seoul, Republic of Korea.
    Kim, S.H.
    Center for Optoelectronic Convergence Systems, KIST (Korean Institute of Science and Technology), Seoul, Republic of Korea.
    Pettersson, Håkan
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS), Tillämpad matematik och fysik (MPE-lab). Lund Univ, Solid State Phys & Nanometer Struct Consortium, Lund, Sweden.
    Wang, Q
    Acreo Swedish ICT AB, Electrum Lab Nano & Microtechnol Fab, Kista, Sweden.
    Song, JD
    Center for Optoelectronic Convergence Systems, KIST (Korean Institute of Science and Technology), Seoul, Republic of Korea.
    Choi, WJ
    Center for Optoelectronic Convergence Systems, KIST (Korean Institute of Science and Technology), Seoul, Republic of Korea.
    InAs/GaAs p-i-p quantum dots-in-a-well infrared photodetectors operating beyond 200 K2014Inngår i: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 50, nr 23, s. 1731-1733Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    High-temperature operating performance of p-i-p quantum dots-in-awell infrared photodetectors (QDIPs) is successfully demonstrated. The optically active region consists of 10 layers of p-doped selfassembled InAs quantum dots (QDs) asymmetrically positioned in In0.15Ga0.85As quantum wells (QWs). The dark current is suppressed by an incorporated superlattice (SL) structure composed of 10 pairs of AlGaAs/GaAs heterostructure. The very low recorded dark current makes the fabricated p-i-p QDIPs suitable for high-temperature operation. The measured photoresponse reveals broad mid-wave infrared (MWIR) detection up to 200 K. © The Institution of Engineering and Technology 2014

  • 50.
    Paschoal Jr., Waldomiro
    et al.
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS), Tillämpad matematik och fysik (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
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS), Tillämpad matematik och fysik (CAMP). Solid State Physics/The Nanometer Structure Consortium, Lund University, Lund, Sweden.
    Electron transport in Mn+ implanted GaAs nanowires2012Konferansepaper (Fagfellevurdert)
    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.

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