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Träfflista för sökning "LAR1:lu srt2:(2010-2011);pers:(Messing Maria)"

Sökning: LAR1:lu > (2010-2011) > Messing Maria

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2.
  • Borgström, Magnus, et al. (författare)
  • Fabrication and characterization of AlP-GaP core-shell nanowires
  • 2011
  • Ingår i: Journal of Crystal Growth. - Elsevier Science BV. - 0022-0248. ; 324:1, s. 290-295
  • Tidskriftsartikel (refereegranskat)abstract
    • We report on the particle assisted synthesis of core-shell AlP-GaP nanowires by use of metal-organic vapor phase epitaxy. The core-shell approach is chosen such as to stabilize the AlP which is highly sensitive to water. The nanowires were investigated by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and Raman spectroscopy. These nanowires have an indirect band-gap and form a type II staggered heterojunction. By designed capping of the AlP cores by GaP, we find the nanowires to be stable for more than a year. (C) 2011 Elsevier B.V. All rights reserved.
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3.
  • Borschel, Christian, et al. (författare)
  • A New Route toward Semiconductor Nanospintronics : Highly Mn-Doped GaAs Nanowires Realized by Ion-Implantation under Dynamic Annealing Conditions
  • 2011
  • Ingår i: Nano letters (Print). - Washington : American Chemical Society (ACS). - 1530-6984. ; 11:9, s. 3935-3940
  • Tidskriftsartikel (refereegranskat)abstract
    • We report on highly Mn-doped GaAs nanowires (NWs) of high crystalline quality fabricated by ion beam implantation, a technique that allows doping concentrations beyond the equilibrium solubility limit. We studied two approaches for the preparation of Mn-doped GaAs NWs: First, ion implantation at room temperature with subsequent annealing resulted in polycrystalline NWs and phase segregation of MnAs and GaAs. The second approach was ion implantation at elevated temperatures. In this case, the single-crystallinity of the GaAs NWs was maintained, and crystalline, highly Mn-doped GaAs NWs were obtained. The electrical resistance of such NWs dropped with increasing temperature (activation energy about 70 meV). Corresponding magnetoresistance measurements showed a decrease at low temperatures, indicating paramagnetism. Our findings suggest possibilities for future applications where dense arrays of GaMnAs nanowires may be used as a new kind of magnetic material system.
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  • Dick, Kimberly, et al. (författare)
  • Parameter space mapping of InAs nanowire crystal structure
  • 2011
  • Ingår i: Journal of Vacuum Science & Technology B. - AVS Science & Technology of Materials, Interfaces, and Processing. - 1071-1023. ; 29:4, s. 04D103
  • Tidskriftsartikel (refereegranskat)abstract
    • Crystal structure and defects have been shown to have a strong impact on III-V nanowire properties. Recently, it was demonstrated that the issue of random stacking and polytypism in semiconductor nanowires can often be controlled using accessible growth parameters (such as temperature, diameter, and V/III ratio). In addition, it has been shown that crystal phase can be tuned selectively between cubic zinc blende and hexagonal wurtzite within individual nanowires of III-V materials such as InAs. In order for such results to be generally applied to different growth setups, it is necessary to fully explore and understand the trends governing crystal phase dependencies on all accessible growth parameters, including how they relate to each other. In this study, the authors have systematically investigated the influence of temperature, diameter, V/III ratio, and total mass flow on the crystal structure of InAs nanowires grown by metal-organic vapor phase epitaxy over a broad parameter range. The authors observed that each of these accessible parameters can affect the resulting crystal structure, and that the trends for each parameter are affected by the magnitude of the others. The authors also noted that most of the parameter dependencies are nonlinear and, in fact, exhibit threshold values at which structure changes discontinuously. By optimizing each of the growth parameters, it is shown that pure ZB or pure WZ phase can be achieved for several different sets of growth conditions. The roles of nucleation kinetics, thermodynamics, and precursor chemistry are also discussed to compare the results to current nanowire growth models. The results in this work should facilitate comparison of data and transfer of knowledge between different growth systems and techniques, which, in turn, should lead to greater understanding of polytypism in nanowires and greater control and freedom in nanowire crystal phase engineering. (C) 2011 American Vacuum Society. DOI: 10.1116/1.3593457
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6.
  • Dick Thelander, Kimberly, et al. (författare)
  • Control of III-V nanowire crystal structure by growth parameter tuning
  • 2010
  • Ingår i: Semiconductor Science and Technology. - IOP Publishing Ltd. - 0268-1242. ; 25:2, s. 024009
  • Tidskriftsartikel (refereegranskat)abstract
    • In this work we investigate the variation of the crystal structure of gold-seeded III-V nanowires with growth parameters, in order to gain a cohesive understanding of these effects. We investigate six III-V materials: GaAs, InAs, GaP, InP, GaSb and InSb, over a variation of growth conditions. All six of these materials exhibit a cubic zinc blende structure in bulk, but twin planes and stacking faults, as well as a hexagonal wurtzite structure, are commonly observed in nanowires. Parameters which may affect the crystal structure include growth temperature and pressure, precursor molar fraction and V/III ratio, nanowire diameter and surface density, and impurity atoms. We will focus on temperature, precursor molar fraction and V/III ratio. Our observations are compared to previous reports in the literature of the III-V nanowire crystal structure, and interpreted in terms of existing models. We propose that changes in the crystal structure with growth parameters are directly related to changes in the stable side facets.
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8.
  • Favre-Nicolin, V., et al. (författare)
  • Analysis of strain and stacking faults in single nanowires using Bragg coherent diffraction imaging
  • 2010
  • Ingår i: New Journal of Physics. - IOP Publishing Ltd. - 1367-2630. ; 12, s. 035013
  • Tidskriftsartikel (refereegranskat)abstract
    • Coherent diffraction imaging (CDI) on Bragg reflections is a promising technique for the study of three-dimensional (3D) composition and strain fields in nanostructures, which can be recovered directly from the coherent diffraction data recorded on single objects. In this paper, we report results obtained for single homogeneous and heterogeneous nanowires with a diameter smaller than 100 nm, for which we used CDI to retrieve information about deformation and faults existing in these wires. We also discuss the influence of stacking faults, which can create artefacts during the reconstruction of the nanowire shape and deformation.
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10.
  • Happonen, Matti, et al. (författare)
  • The comparison of particle oxidation and surface structure of diesel soot particles between fossil fuel and novel renewable diesel fuel
  • 2010
  • Ingår i: Fuel. - Elsevier Science Ltd. - 0016-2361. ; 89:12, s. 4008-4013
  • Tidskriftsartikel (refereegranskat)abstract
    • Conventional fossil diesel fuel and renewable diesel fuel based on hydrotreated vegetable oils (HVO) were compared regarding the oxidation characteristics of the generated soot particulate. The comparison was performed by utilizing a high-temperature oxidation tandem differential mobility analyser in which monodisperse soot aerosol was first selected and then heated in a high-temperature furnace. The particle size reduction caused by oxidation during the furnace treatment was then measured as a function of furnace temperature. The results indicate that soot oxidation is very similar between the studied fuels. This is supported by the obtained HR-TEM images and EELS-spectra which were practically indistinguishable between different fuels and engine conditions. The similar oxidation properties and surface structure between fossil and HVO-based diesel fuels imply that the oxidative aftertreatment devices designed for fossil diesel should work well also with the studied renewable diesel fuel. (C) 2010 Elsevier Ltd. All rights reserved.
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