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  • 1.
    Ahlberg, Patrik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Hinnemo, Malkolm
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Song, Man
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Gao, Xindong
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Olsson, Jörgen
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Zhang, Shi-Li
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Zhang, Zhi-Bin
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    A two-in-one process for reliable graphene transistors processed with photolithography2015In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 107, no 20, article id 203104Article in journal (Refereed)
    Abstract [en]

    Research on graphene field-effect transistors (GFETs) has mainly relied on devices fabricated using electron-beam lithography for pattern generation, a method that has known problems with polymer contaminants. GFETs fabricated via photo-lithography suffer even worse from other chemical contaminations, which may lead to strong unintentional doping of the graphene. In this letter, we report on a scalable fabrication process for reliable GFETs based on ordinary photo-lithography by eliminating the aforementioned issues. The key to making this GFET processing compatible with silicon technology lies in a two-in-one process where a gate dielectric is deposited by means of atomic layer deposition. During this deposition step, contaminants, likely unintentionally introduced during the graphene transfer and patterning, are effectively removed. The resulting GFETs exhibit current-voltage characteristics representative to that of intrinsic non-doped graphene. Fundamental aspects pertaining to the surface engineering employed in this work are investigated in the light of chemical analysis in combination with electrical characterization.

  • 2. Ahmed, S.
    et al.
    Nawaz, R.
    Syed, W. A.
    Taiq, R.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Amirov, K.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Larsson, U.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Annealing characteristics of electrically isolated InGaAsP devices2007In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 91, no 6, p. 062112-Article in journal (Refereed)
    Abstract [en]

    The authors report on the effects of fluorine implants on the sheet resistivity of n-type InGaAsP layers grown lattice matched to InP by metal organic molecular beam epitaxy. Projected range matched fluorine ions are implanted at multiple energies and single MeV energy at room temperature (RT) and 77 K in both cases. Hall and resistivity measurements are carried out for the van der Pauw samples and the evolution of sheet resistivity (R-s) as a function of annealing temperature was studied in both cases. Fluorine multienergy implantation at 77 K produces higher as-implanted resistivity layers of similar to 10(7) Omega/square compared to RT implants. It is further observed that RT and 77 K implants recover to their preimplanted sheet resistivity values as soon as they are annealed at temperatures higher than 500 degrees C. Substrate temperature and collision cascade density due to multiple energy implants are found to play an important role to optimize the isolation process.

  • 3.
    Aijaz, Asim
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Kubart, Tomas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Ion induced stress relaxation in dense sputter-deposited DLC thin films2017In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 111, no 5, article id 051902Article in journal (Refereed)
    Abstract [en]

    Deposition of high-density and low-stress hydrogen-free diamond like carbon (DLC) thin films is demonstrated using a pulsed ionized sputtering process. This process is based on high power impulse magnetron sputtering, and high C ionization is achieved using Ne as the sputtering gas. The intrinsic compressive stress and its evolution with respect to ion energy and ion flux are explained in terms of the compressive stress based subplantation model for DLC growth by Davis. The highest mass density was similar to 2.7 g/cm(3), and the compressive stresses did not exceed similar to 2.5 GPa. The resulting film stresses are substantially lower than those achieved for the films exhibiting similar mass densities grown by filtered cathodic vacuum arc and pulsed laser deposition methods. This unique combination of high mass density and low compressive stress is attributed to the ion induced stress relaxation during the pulse-off time which corresponds to the post thermal spike relaxation timescales. We therefore propose that the temporal ion flux variations determine the magnitude of the compressive stress observed in our films. Published by AIP Publishing.

  • 4. Andersson, D. A.
    et al.
    Simak, S. I.
    Skorodumova, Natalia V.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Abrikosov, I. A.
    Johansson, Börje
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Redox properties of CeO2-MO2 (M=Ti, Zr, Hf, or Th) solid solutions from first principles calculations2007In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 90, no 3, p. 031909-Article in journal (Refereed)
    Abstract [en]

    The authors have used density functional theory calculations to investigate how the redox thermodynamics and kinetics of CeO2 are influenced by forming solid solutions with TiO2, ZrO2, HfO2, and ThO2. Reduction is facilitated by dissolving TiO2 (largest improvement), HfO2, or ZrO2 (least improvement), while ThO2 makes reduction slightly more difficult. The migration barrier is much lower in the neighborhood of a Ti (largest decrease), Hf, or Zr (least decrease), while the binding energy of solute ions and vacancies increases in the same sequence. They rationalize the properties of ceria solid solutions in terms of defect cluster relaxations.

  • 5. Andersson, R
    et al.
    Baglin, J
    Dempsey, J
    Hammer, W
    d'Heurle, F
    Petersson, CS
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Nucleation controlled thin film interactions: Three silicides1979In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 35, p. 285-Article in journal (Refereed)
  • 6.
    Anversa, Jonas
    et al.
    Univ Fed Santa Maria, Dept Fis, BR-97105900 Santa Maria, RS, Brazil.;Fac Meridional, Escola Engn Civil, BR-99070220 Passo Fundo, RS, Brazil..
    Chakraborty, Sudip
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Piquini, Paulo
    Univ Fed Santa Maria, Dept Fis, BR-97105900 Santa Maria, RS, Brazil..
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Royal Inst Technol KTH, Dept Mat & Engn, Appl Mat Phys, S-10044 Stockholm, Sweden..
    High pressure driven superconducting critical temperature tuning in Sb2Se3 topological insulator2016In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 108, no 21, article id 212601Article in journal (Refereed)
    Abstract [en]

    In this letter, we are reporting the change of superconducting critical temperature in Sb2Se3 topological insulator under the influence of an external hydrostatic pressure based on first principles electronic structure calculations coupled with Migdal-Eliashberg model. Experimentally, it was shown previously that Sb2Se3 was undergoing through a transition to a superconducting phase when subjected to a compressive pressure. Our results show that the critical temperature increases up to 6.15K under the pressure unto 40GPa and, subsequently, drops down until 70 GPa. Throughout this pressure range, the system is preserving the initial Pnma symmetry without any structural transformation. Our results suggest that the possible relevant mechanism behind the superconductivity in Sb2Se3 is primarily the electron-phonon coupling. Published by AIP Publishing.

  • 7.
    Araujo, C. Moyses
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Kapilashrami, Mukes
    Jun, Xu
    Jayakumar, O. D.
    Nagar, Sandeep
    Wu, Yan
    Århammar, Cecilia
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Johansson, Börje
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Belova, Lyubov
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Gehring, Gillian A.
    Rao, K. V.
    Room temperature ferromagnetism in pristine MgO thin films2010In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 96, no 23, p. 232505-Article in journal (Refereed)
    Abstract [en]

    Robust ferromagnetic ordering at, and well above room temperature is observed in pure transparent MgO thin films (<170 nm thick) deposited by three different techniques. Careful study of the wide scan x-ray photoelectron spectroscopy rule out the possible presence of any magnetic contaminants. In the magnetron sputtered films, we observe magnetic phase transitions as a function of film thickness. The maximum saturation magnetization of 5.7 emu/cm(3) is measured on a 170 nm thick film. The films above 500 nm are found to be diamagnetic. Ab initio calculations suggest that the ferromagnetism is mediated by cation vacancies.

  • 8.
    Araujo, Carlos Moyses
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Condensed Matter Theory.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Condensed Matter Theory.
    Osorio Guillén, Jorge Mario
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Condensed Matter Theory.
    Jena, P
    Role of titanium in hydrogen desorption in crystalline sodium alanate2005In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 86, no 25, article id 251913Article in journal (Refereed)
    Abstract [en]

    The role of Ti in improving the thermodynamics of hydrogen desorption in crystalline sodium alanate (NaAlH4) has been investigated by using the density functional theory. The total energy calculations reveal that Ti prefers to occupy the Na site over that of the Al site when the atomic energies are used as the reference. However, the use of the cohesive energies of Al, Na, and Ti leads to the Al site being the least unfavourable site. Irrespective of whether Ti occupies the Na or the Al site, the energy necessary to remove a hydrogen atom from Ti substituted sodium alanate is significantly lowered from that of the pure alanate. The understanding gained here may help in designing hydrogen storage materials suitable for industrial applications.

  • 9.
    Araújo, C. Moysés
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Condensed Matter Theory.
    Scheicher, Ralph H.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Condensed Matter Theory.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Condensed Matter Theory.
    Thermodynamic analysis of hydrogen sorption reactions in Li-Mg-N-H systems2008In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 92, no 2, p. 021907-Article in journal (Refereed)
    Abstract [en]

    We report a comprehensive first-principles study of the thermodynamics of the hydrogen release reaction from xLiH-yMg(NH2)(2) mixtures involving the composition ratios (x=2, y=1), (x=8, y=3), and (x=12, y=3), with special emphasis on the effect of the different intermediate steps. For all three mixing ratios of LiH/Mg(NH2)(2) we find that the hydrogen release is initiated by the same reaction with an enthalpy of 46.1 kJ/mol of H-2 in excellent agreement with recent experimental results. Additionally, we also investigated the substitution of LiH by MgH2 as reaction partner of Mg(NH2)(2) in the fully hydrogenated state.

  • 10.
    Araújo, C. Moysés
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Scheicher, Ralph H.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Jena, Puru
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    On the structural and energetic properties of the hydrogen absorber Li2Mg(NH)22007In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 91, no 9, p. 091924-Article in journal (Refereed)
    Abstract [en]

    The authors have performed density functional theory based calculations of several possible conformations for the crystal structure of Li2Mg(NH)2 and they confirm the α phase, resolved from both x-ray and neutron diffraction data, as the ground-state configuration. It is also found that although the N-H bond is stronger in Li2Mg(NH)2 than in Li2NH, hydrogen release from Li2Mg(NH)2/LiH mixture displays more favorable thermodynamics than that from the Li2NH/LiH mixture. The insights gained from this seemingly counterintuitive result should prove helpful in the search for promising hydrogen storage materials.

  • 11.
    Arnalds, Unnar B.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Ahlberg, Martina
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Brewer, Matthew S.
    Kapaklis, Vassilios
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Papaioannou, Evangelos Th.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Karimipour, Masoud
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Korelis, Panagiotis
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Stein, Aaron
    Olafsson, Sveinn
    Hase, Thomas P. A.
    Hjörvarsson, Björgvin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Thermal transitions in nano-patterned XY-magnets2014In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 105, no 4, p. 042409-Article in journal (Refereed)
    Abstract [en]

    We have fabricated ultra-thin disc shaped islands wherein shape anisotropy confines the moment to the island plane, creating XY-like superspins. At low temperatures, the superspins are blocked, and, as the temperature is increased, they undergo a transition into a superparamagnetic state. The onset of this dynamic superspin state scales with the diameter of the islands, and it persists up to a temperature governed by the intrinsic ordering temperature of the island material defining a range in temperature in which dynamic behavior of the magnetic islands can be obtained.

  • 12.
    Arnalds, Unnar
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Farhan, Alan
    Paul Scherrer Institut.
    Chopdekar, Rajesh
    Paul Scherrer Institut.
    Kapaklis, Vassilios
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Balan, Ana
    Paul Scherrer Institut.
    Papaioannou, Evangelos
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Ahlberg, Martina
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Nolting, Frithjof
    Paul Scherrer Institut.
    Heyderman, Laura
    Paul Scherrer Institut.
    Hjörvarsson, Björgvin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Thermalized ground state of artificial kagome spin ice building blocks2012In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 101, no 11, p. 112404-Article in journal (Other academic)
    Abstract [en]

    We present a direct magnetic imaging study on the thermal macrospin ordering of artificial kagome spin ice building blocks. Using photoemission electron microscopy, employing x-ray magnetic circular dichroism, we are able to resolve the single domain magnetic nature of the macrospins and determine the states of the combined building block structures. The nano-patterning and material selection allows thermally activated magnetization reversal for the macrospins to occur. The ordering of the macrospins is dominated by the ground state, consistent with a thermal ground state ordering. This work paves the way for the realization of extended artificial spin ice structures exhibiting experimentally accessible thermal behavior

  • 13. Baglin, J
    et al.
    d'Heurle, F
    Petersson, CS
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    An alterntive marker experiment in the formation of Mo and W silicides1978In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 33, p. 289-Article in journal (Refereed)
  • 14. Baglin, J
    et al.
    d'Heurle, F
    Petersson, CS
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    The formation of silicides from thin films of some rare-earth metals1980In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 36, p. 594-Article in journal (Refereed)
  • 15.
    Barankova, Hana
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity. BB Plasma Design AB, SE-75643 Uppsala, Sweden..
    Bardos, Ladislav
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity. BB Plasma Design AB, SE-75643 Uppsala, Sweden..
    Bardos, A.
    BB Plasma Design AB, SE-75643 Uppsala, Sweden..
    Magnetized hollow cathode activated magnetron2015In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 107, no 15, article id 153501Article in journal (Refereed)
    Abstract [en]

    Planar magnetron in which the target is coupled with a magnetized hollow cathode is presented. Detailed principles of such arrangements are explained. The hollow cathode activated magnetron produces intense and stable plasmas in a wider interval of the working gas pressures as compared to the conventional magnetrons at the same power. The developed arrangements enhance sputtering from the magnetron target by the high-density hollow cathode plasma and increase the number of sputtered/evaporated species. Results of the test experiments of these arrangements on a commercial planar magnetron with the Ti target are presented and their capabilities discussed.

  • 16. Bardos, Ladislav
    et al.
    Berg, Sören
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Blom, Hans-Olof
    Superhigh-rate plasma jet etching of silicon1989In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 55, no 16, p. 1615-1617Article in journal (Refereed)
  • 17.
    Bayrak Pehlivan, I.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Runnerstrom, E. L.
    The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA, USA och Dept of Materials Science and Engineering, University of California, Berkeley, CA, USA.
    Li, Shuyi
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Milliron, D. J.
    The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
    Granqvist, Claes-Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    A polymer electrolyte with high luminous transmittance and low solar throughput: Polyethyleneimine-lithium bis(trifluoromethylsulfonyl) imide with In2O3:Sn nanocrystals2012In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 100, no 24, p. 241902-Article in journal (Refereed)
    Abstract [en]

    Chemically prepared similar to 13-nm-diameter nanocrystals of In2O3:Sn were included in a polyethyleneiminelithium bis(trifluoromethylsulfonyl) imide electrolyte and yielded high haze-free luminous transmittance and strong near-infrared absorption without deteriorated ionic conductivity. The optical properties could be reconciled with effective medium theory, representing the In2O3:Sn as a free electron plasma with tin ions screened according to the random phase approximation corrected for electron exchange. This type of polymer electrolyte is of large interest for opto-ionic devices such as laminated electrochromic smart windows.

  • 18.
    Berggren, Lars
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar A
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics. Fasta tillståndets fysik.
    Optical Charge Transfer Absorption in Lithium-intercalated Tungsten Oxide Thin Films2006In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, no 88, p. 081906-Article in journal (Refereed)
    Abstract [en]

    Amorphous tungsten oxide exhibits electrochromism when intercalated with protons or lithium ions.Thin films of the material were prepared by dc magnetron sputtering and subsequentlyelectrochemically intercalated with lithium. The optical absorption in the wavelength range300 to 2500 nm was measured for a number of lithium concentrations. All the spectra can be fittedby a superposition of three Gaussian peaks, representing the three possible electronic transitionsbetween W6+, W5+, and W4+ sites. The variation of the peak strength with lithium concentration isconsistent with the predictions of a statistical theory.

  • 19. Bleskov, I. D.
    et al.
    Smirnova, A
    Vekilov, Kh
    Korzhavyi, A
    Johansson, Börje
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Katsnelson, M
    Vitos, Levente
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Abrikosov, A
    Isaev, E. I.
    Ab initio calculations of elastic properties of Ru1-xNixAl superalloys2009In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 94, no 16, p. 161901-Article in journal (Refereed)
    Abstract [en]

    Ab initio total energy calculations based on the exact muffin-tin orbitals method, combined with the coherent potential approximation, have been used to study the thermodynamical and elastic properties of substitutional refractory Ru1-xNixAl alloys. We have found that the elastic constants C-' and C-11 exhibit pronounced peculiarities near the concentration of about 40 at. % Ni, which we ascribe to electronic topological transitions. Our suggestion is supported by the Fermi surface calculations in the whole concentration range. Results of our calculations show that one can design Ru-Ni-Al alloys substituting Ru by Ni (up to 40 at. %) with almost invariable elastic constants and reduced density.

  • 20.
    Blomqvist, Andreas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Araújo, C. Moysés
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Jena, Puru
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Dehydrogenation from 3d-transition-metal-doped NaAlH4: Prediction of catalysts2007In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 90, no 14, p. 141904-Article in journal (Refereed)
    Abstract [en]

    A fundamental understanding of the role of catalysts in improving the kinetics and thermodynamics of hydrogen sorption in NaAlH4 is the key for using this material in hydrogen storage. The authors present a systematic theoretical study of energies needed to desorb hydrogen in 3d transition metal (Sc-Cu)-doped NaAlH4. They show that Cr and Fe atoms can be far more effective catalysts than Ti in desorbing hydrogen. The role of the 3d metal atoms in improving the thermodynamics of dehydrogenation is attributed to a significant shortening of the bond length with neighboring Al atoms.

  • 21.
    Bostrom, Cecilia
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Ekergård, Boel
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Leijon, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Electric resonance-rectifier circuit for renewable energy conversion2012In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 100, no 4, p. 043511-Article in journal (Refereed)
    Abstract [en]

    Variable speed generators are used more frequently for converting the energy from renewable energy sources to electric energy. The power production form a variable speed generator is dependent on the electrical damping of the generator. In this paper, a resonance circuit connected to a direct driven linear generator used for wave energy utilization is investigated. At resonance, the electrical damping in the generator increases which results in an increased power production. The results show that resonance can be achieved with the suggested circuit.

  • 22.
    Brohede, Ulrika
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Strömme, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Percolating ion transport in binary mixtures with high dielectric loss2006In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 88, article id 214103Article in journal (Refereed)
    Abstract [en]

    We investigate the ion transportpercolationproperties of a binary system of an ion conductor (NaCl) and an insulator (ethyl cellulose) for which the ac component of the conductivity is non-negligible over the entire measured frequency range. We find that the dc conductivity, extracted from a well-defined range of frequencies, can be described by a low percolation threshold, ϕc=0.06 three-dimensional conducting network. The low ϕc was explained by the water-layer-assisted ion conduction in micrometer-sized ethyl cellulose channels between NaCl grains. The present findings provide valuable knowledge for the analysis and design of a broad class of ion conducting functional materials.

  • 23. Carlegrim, Elin
    et al.
    Kanciurzewska, Anna
    Nordblad, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Fahlman, Mats
    Air-stable organic-based semiconducting room temperature thin film magnet for spintronics applications2008In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 92, no 16, p. 163308-Article in journal (Refereed)
    Abstract [en]

    Herein, we report on a preparation method of vanadium tetracyanoethylene, V(TCNE)(x), an organic-based semiconducting room temperature thin film magnet. Previously, this compound has been reported to be extremely air sensitive but this preparation method leads to V(TCNE)(x), which can retain its magnetic ordering at least several weeks in air. The electronic structure has been studied by photoelectron spectroscopy and the magnetic properties by superconducting quantum interference device. The properties mentioned above, in combination with complete spin polarization, makes this air-stable V(TCNE)(x) a very promising material for spintronic devices.

  • 24.
    Chang, Bo
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Zhou, Quan
    Aalto University, Finland.
    Ras, Robin
    Aalto University, Finland.
    Shah, Ali
    Aalto University, Finland.
    Wu, Zhigang
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Hjort, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Sliding droplets on hydrophilic/superhydrophobic patterned surfaces for liquid deposition2016In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 108, no 15, article id 154102Article in journal (Refereed)
    Abstract [en]

    A facile gravity-induced sliding droplets method is reported for deposition of nanoliter sized droplets on hydrophilic/superhydrophobic patterned surface. The deposition process is parallel where multiple different liquids can be deposited simultaneously. The process is also high-throughput, having a great potential to be scaled up by increasing the size of the substrate.

  • 25.
    Chen, Si
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Jokilaakso, Nima
    Björk, Per
    Eriksson Karlström, Amelie
    Zhan, Shi-Li
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    A two-terminal silicon nanoribbon field-effect pH sensor2010In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 97, no 26, p. 264102-Article in journal (Refereed)
    Abstract [en]

    This paper reports on a two-terminal silicon nanoribbon (SiNR) field-effect pH sensor operated in electrolyte. Observed experimentally and confirmed by modeling, the sensor is activated by self-gating with a gate bias set by the potential difference of the two terminals. The effect of this gate bias on the SiNR conductance is modulated by the potential drop over the electrical double layer (EDL) established on the SiNR surface, similarly to the threshold voltage modulation by EDL in a three-terminal SiNR field-effect transistor with an independent gate electrode. The potential drop over EDL is determined by the pH value of the electrolyte.

  • 26.
    Chen, Si
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Zhang, Zhi-Bin
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Ma, Laipeng
    Shenyang National Laboratory, Kina.
    Ahlberg, Patrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Gao, Xindong
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Qiu, Zhijun
    Fudan University, Kina.
    Wu, Dongping
    Fudan University, Kina.
    Ren, Wencai
    Institute of Metal Research, CAS, China.
    Cheng, Hui-Ming
    Institute of Metal Research, CAS, China.
    Zhang, Shili
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    A graphene field-effect capacitor sensor in electrolyte2012In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 101, no 15, p. 154106-Article in journal (Refereed)
    Abstract [en]

    The unique electronic properties of graphene are exploited for field-effect sensing in both capacitor and transistor modes when operating the sensor device in electrolyte. The device is fabricated using large-area graphene thin films prepared by means of layer-by-layer stacking. Although essentially the same device, its operation in the capacitor mode is found to yield more information than in the transistor mode. The capacitor sensor can simultaneously detect the variations of surface potential and electrical-double-layer capacitance at the graphene/electrolyte interface when altering the ion concentration. The capacitor-mode operation further facilitates studies of the molecular binding-adsorption kinetics by monitoring the capacitance transient

  • 27.
    Cheng, Kai
    et al.
    Dalian Univ Technol, Minist Educ, Key Lab Mat Modificat Laser Ion & Electron Beams, Dalian 116024, Peoples R China.
    Guo, Yu
    Dalian Univ Technol, Minist Educ, Key Lab Mat Modificat Laser Ion & Electron Beams, Dalian 116024, Peoples R China.
    Han, Nannan
    Dalian Univ Technol, Minist Educ, Key Lab Mat Modificat Laser Ion & Electron Beams, Dalian 116024, Peoples R China.
    Jiang, Xue
    Dalian Univ Technol, Minist Educ, Key Lab Mat Modificat Laser Ion & Electron Beams, Dalian 116024, Peoples R China.
    Zhang, Junfeng
    Shanxi Normal Univ, Sch Phys & Informat Engn, Linfen 041000, Peoples R China.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Su, Yan
    Dalian Univ Technol, Minist Educ, Key Lab Mat Modificat Laser Ion & Electron Beams, Dalian 116024, Peoples R China.
    Zhao, Jijun
    Dalian Univ Technol, Minist Educ, Key Lab Mat Modificat Laser Ion & Electron Beams, Dalian 116024, Peoples R China.
    2D lateral heterostructures of group-III monochalcogenide: Potential photovoltaic applications2018In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 112, no 14, article id 143902Article in journal (Refereed)
    Abstract [en]

    Solar photovoltaics provides a practical and sustainable solution to the increasing global energy demand. Using first-principles calculations, we investigate the energetics and electronic properties of two-dimensional lateral heterostructures by group-III monochalcogenides and explore their potential applications in photovoltaics. The band structures and formation energies from supercell calculations demonstrate that these heterostructures retain semiconducting behavior and might be synthesized in laboratory using the chemical vapor deposition technique. According to the computed band offsets, most of the heterojunctions belong to type II band alignment, which can prevent the recombination of electron-hole pairs. Besides, the electronic properties of these lateral heterostructures can be effectively tailored by the number of layers, leading to a high theoretical power conversion efficiency over 20%.

  • 28.
    Cheng, Shi
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microwave and Terahertz Technology.
    Rydberg, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microwave and Terahertz Technology.
    Hjort, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Wu, Zhigang
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Liquid metal stretchable unbalanced loop antenna2009In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 94, no 14, p. 144103-Article in journal (Refereed)
    Abstract [en]

    We present a 2.4 GHz unbalanced loop antenna that can be stretched along multiple dimensions simultaneously. It was realized by incorporating room temperature liquid metal alloy into microstructured channels in an elastic material. The demonstrated prototype exhibits a stretchability of up to 40% along two orthogonal orientations as well as foldability and twistability. Port impedance and radiation characteristics of the nonstretched and stretched antenna were studied numerically and experimentally. Measured results indicate a radiation efficiency of more than 80%.

  • 29. Da, Zhang
    et al.
    Xingdong, Gao
    Si, Chen
    Hans, Norström
    Ulf, Smith
    Paul, Solomon
    Shili, Zhang
    Zhen, Zhang
    An ion-gated bipolar amplifier for ion sensing with enhanced signal and improved noise performance2014In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118Article in journal (Refereed)
  • 30. Dantas, N. Souza
    et al.
    de Almeida, J. S.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Condensed Matter Theory.
    Ahuja, R.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Condensed Matter Theory.
    Persson, C.
    da Silva, A. Ferreira
    Novel semiconducting materials for optoelectronic applications: Al1-xTlxN alloys2008In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 92, no 12, p. 121914-Article in journal (Refereed)
    Abstract [en]

    We proprose the ternary semiconducting Al1-xTlxN alloys as new material for optoelectronic applications. Ab initio calculations have been performed to study structural, electronic, and optical properties of the theoretically designed thallium-aluminum based nitride alloys. We found that the lattice constants vary linearly with thallium composition whereas the band gap and absorption edge span from ultraviolet to infrared energy region by increasing thallium content which make the predicted material interesting for infrared optical devices among other technological applications.

  • 31.
    de Almeida, J. S.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Kim, D. Y.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Ortiz, C.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Klintenberg, Mattias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    On the dynamical stability and metallic behavior of YH3 under pressure2009In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 94, no 25, p. 251913-Article in journal (Refereed)
    Abstract [en]

    Wereport on the behavior of structural and electronic properties ofyttrium trihydride under pressure using first principles calculations. We showthat YH3 undergoes a structural transformation and its high pressurephase is dynamically stable under pressure since the peak atthe imaginary frequencies of the phonon density of states, whichaccount for the structural instability disappears at high pressure. Additionally,our GW calculations indicate a metallization of the high pressurecubic phase of YH3.

  • 32. de Sousa Pires, Jorge
    et al.
    Ali, MP
    Crowder, B
    d'Heurle, F
    Petersson, CS
    Stolt, Lars
    Tove, PA
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Measurement of the rectifying barrier heights of the various iridium silicides with n-silicon1979In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 35, p. 202-Article in journal (Refereed)
  • 33. de Sousa Pires, Jorge
    et al.
    d'Heurle, F
    Norde, Herman
    Petersson, CS
    Tove, PA
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Measurement of the rectrifying barrier heights of various rhodium silicides with n-silicon1980In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 36Article in journal (Refereed)
  • 34. De Toro, J. A.
    et al.
    Lee, S. S.
    Salazar, D.
    Cheong, J. L.
    Normile, P. S.
    Muniz, P.
    Riveiro, J. M.
    Hillenkamp, M.
    Tournus, F.
    Tamion, A.
    Nordblad, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    A nanoparticle replica of the spin-glass state2013In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 102, no 18, p. 183104-Article in journal (Refereed)
    Abstract [en]

    A simple single-phase material, a random close-packed (volume fraction 67%) ensemble of highly monodisperse bare maghemite (gamma-Fe2O3) nanoparticles, is shown to exhibit ideal superspin-glass behavior (mimicking that of model spin-glasses), namely, an unprecedentedly sharp onset of the absorption component of the ac susceptibility, narrow memory dips in the zero-field-cooled magnetization and a spin-glass characteristic field-dependence of the magnetic susceptibility. This ideal behavior is attributed to the remarkably narrow dispersion in particle size and to the highly dense and spatially homogeneous configuration ensured by the random close-packed arrangement. This material is argued to constitute the closest nanoparticle analogue to a conventional (atomic) magnetic state found to date. 

  • 35. Dreiser, Jan
    et al.
    Westerström, Rasmus
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Piamonteze, Cinthia
    Nolting, Frithjof
    Rusponi, Stefano
    Brune, Harald
    Yang, Shangfeng
    Popov, Alexey
    Dunsch, Lothar
    Greber, Thomas
    X-ray induced demagnetization of single-molecule magnets2014In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 105, no 3, p. 032411-Article in journal (Refereed)
    Abstract [en]

    Low-temperature x-ray magnetic circular dichroism measurements on the endohedral single-molecule magnet DySc2N@C-80 at the Dy M-4,M-5 edges reveal a shrinking of the opening of the observed hysteresis with increasing x-ray flux. Time-dependent measurements show that the exposure of the molecules to x-rays resonant with the Dy M-5 edge accelerates the relaxation of magnetization more than off-resonant x-rays. The results cannot be explained by a homogeneous temperature rise due to x-ray absorption. Moreover, the observed large demagnetization cross sections indicate that the resonant absorption of one x-ray photon induces the demagnetization of many molecules.

  • 36.
    Farmand, Maryam
    et al.
    Lawrence Berkeley Natl Lab, Adv Light Source, Berkeley, CA 94720 USA..
    Celestre, Richard
    Lawrence Berkeley Natl Lab, Adv Light Source, Berkeley, CA 94720 USA..
    Denes, Peter
    Lawrence Berkeley Natl Lab, Adv Light Source, Berkeley, CA 94720 USA..
    Kilcoyne, A. L. David
    Lawrence Berkeley Natl Lab, Adv Light Source, Berkeley, CA 94720 USA..
    Marchesini, Stefano
    Lawrence Berkeley Natl Lab, Adv Light Source, Berkeley, CA 94720 USA..
    Padmore, Howard
    Lawrence Berkeley Natl Lab, Adv Light Source, Berkeley, CA 94720 USA..
    Tyliszczak, Tolek
    Lawrence Berkeley Natl Lab, Adv Light Source, Berkeley, CA 94720 USA..
    Warwick, Tony
    Lawrence Berkeley Natl Lab, Adv Light Source, Berkeley, CA 94720 USA..
    Shi, Xiaowen
    Lawrence Berkeley Natl Lab, Adv Light Source, Berkeley, CA 94720 USA.;Univ Oregon, Dept Phys, Eugene, OR 97401 USA..
    Lee, James
    Lawrence Berkeley Natl Lab, Adv Light Source, Berkeley, CA 94720 USA.;Univ Oregon, Dept Phys, Eugene, OR 97401 USA..
    Yu, Young-Sang
    Lawrence Berkeley Natl Lab, Adv Light Source, Berkeley, CA 94720 USA.;Univ Illinois, Dept Chem, Chicago, IL 60607 USA..
    Cabana, Jordi
    Univ Illinois, Dept Chem, Chicago, IL 60607 USA..
    Joseph, John
    Lawrence Berkeley Natl Lab, Div Engn, Berkeley, CA 94720 USA..
    Krishnan, Harinarayan
    Lawrence Berkeley Natl Lab, Computat Res Div, Berkeley, CA 94720 USA..
    Perciano, Talita
    Lawrence Berkeley Natl Lab, Computat Res Div, Berkeley, CA 94720 USA..
    Maia, Filipe R.N.C.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Molecular biophysics.
    Shapiro, David A.
    Lawrence Berkeley Natl Lab, Adv Light Source, Berkeley, CA 94720 USA..
    Near-edge X-ray refraction fine structure microscopy2017In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 110, no 6, article id 063101Article in journal (Refereed)
    Abstract [en]

    We demonstrate a method for obtaining increased spatial resolution and specificity in nanoscale chemical composition maps through the use of full refractive reference spectra in soft x-ray spectro- microscopy. Using soft x-ray ptychography, we measure both the absorption and refraction of x-rays through pristine reference materials as a function of photon energy and use these reference spectra as the basis for decomposing spatially resolved spectra from a heterogeneous sample, thereby quantifying the composition at high resolution. While conventional instruments are limited to absorption contrast, our novel refraction based method takes advantage of the strongly energy dependent scattering cross-section and can see nearly five-fold improved spatial resolution on resonance.

  • 37. Ferhat, M
    et al.
    Zaoui, A
    Ahuja, R
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Magnetism and band gap narrowing in Cu-doped ZnO2009In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 94, no 14, p. 142502-Article in journal (Refereed)
    Abstract [en]

    First-principles calculations based on density functional theory are performed to study the magnetic, electronic, and optical properties of ZnO doped with 6.25%, 12.5%, and 18.75% of Cu. The Cu dopants are found spin polarized, and a net magnetic moment of 0.57 mu(B) is found for Cu at a composition of 6.25%. The calculations confirm an appreciable band gap reduction in ZnO in agreement with recent experimental results. The analysis of the partial density of states reveals that ferromagnetism and narrowing of ZnO band gap are due principally to the strong p-d mixing of O and Cu.

  • 38.
    Fornell, Anna
    et al.
    Lund Univ, Dept Biomed Engn, Lund, Sweden..
    Cushing, Kevin
    Lund Univ, Dept Biomed Engn, Lund, Sweden..
    Nilsson, Johan
    Lund Univ, Dept Biomed Engn, Lund, Sweden..
    Tenje, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology. Uppsala University, Science for Life Laboratory, SciLifeLab. Lund Univ, Dept Biomed Engn, Lund, Sweden.
    Binary particle separation in droplet microfluidics using acoustophoresis2018In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 112, no 6, article id 063701Article in journal (Refereed)
    Abstract [en]

    We show a method for separation of two particle species with different acoustic contrasts originally encapsulated in the same droplet in a continuous two-phase system. This was realized by using bulk acoustic standing waves in a 380 mu m wide silicon-glass microfluidic channel. Polystyrene particles (positive acoustic contrast particles) and in-house synthesized polydimethylsiloxane (PDMS) particles (negative acoustic contrast particles) were encapsulated inside water-in-oil droplets either individually or in a mixture. At acoustic actuation of the system at the fundamental resonance frequency, the polystyrene particles were moved to the center of the droplet (pressure node), while the PDMS particles were moved to the sides of the droplet (pressure anti-nodes). The acoustic particle manipulation step was combined in series with a trifurcation droplet splitter, and as the original droplet passed through the splitter and was divided into three daughter droplets, the polystyrene particles were directed into the center daughter droplet, while the PDMS particles were directed into the two side daughter droplets. The presented method expands the droplet microfluidics tool-box and offers new possibilities to perform binary particle separation in droplet microfluidic systems.

  • 39. Fu, Yu
    et al.
    Barsukov, I.
    Meckenstock, R.
    Lindner, J.
    Raanaei, H.
    Hjörvarsson, Björgvin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Farle, M.
    Mechanism of tailored magnetic anisotropy in amorphous Co68Fe24Zr8 thin films2014In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 104, no 7, p. 072409-Article in journal (Refereed)
    Abstract [en]

    The mechanism of tailored magnetic anisotropy in amorphous Co68Fe24Zr8 thin films was investigated by ferromagnetic resonance (FMR) on samples deposited without an applied magnetic field, with an out-of-plane field and an in-plane field. Analysis of FMR spectra profiles, high frequency susceptibility calculations, and statistical simulations using a distribution of local uniaxial magnetic anisotropy reveal the presence of atomic configurations with local uniaxial anisotropy, of which the direction can be tailored while the magnitude remains at an intrinsically constant value of 3.0(2) kJ/m(3). The in-plane growth field remarkably sharpens the anisotropy distribution and increases the sample homogeneity. The results benefit designing multilayer spintronic devices based on highly homogeneous amorphous layers with tailored magnetic anisotropy.

  • 40. Ganguli, Nirmal
    et al.
    Dasgupta, Indra
    Sanyal, Biplab
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    The making of ferromagnetic Fe doped ZnO nanoclusters2009In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 94, no 19, p. 192503-Article in journal (Refereed)
    Abstract [en]

    In this letter, the authors present a study of the energetics and magnetic interactions in Fe doped ZnO clusters by ab initio density functional calculations. The results indicate that defects under suitable conditions can induce ferromagnetic interactions between the dopant Fe atoms whereas antiferromagnetic coupling dominates in a neutral defect-free cluster. The calculations also reveal an unusual ionic state of the dopant Fe atom residing at the surface of the cluster, a feature that is important to render the cluster ferromagnetic.

  • 41. Ghosh, S.
    et al.
    Sanyal, Biplab
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Das, G. P.
    Density functional calculations of hole induced long ranged ferromagnetic ordering in Mn doped Cd28Se28 nanocluster2010In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 96, no 5, p. 052506-Article in journal (Refereed)
    Abstract [en]

    We have investigated the possibility of long ranged ferromagnetic ordering in Mn doped Cd28Se28 nanocluster using density functional approach. Following the band repulsion theory we have explained that magnetic coupling between Mn atoms substituted in Cd sites is antiferromagnetic and short ranged. However, long ranged ferromagnetic coupling is possible via additional hole doping which leads to the spin splitting of the valence band. In this class of magnetic nanoclusters, additional hole doping induces spin polarization of host states at large distance. This property can lead to molecular magnets with tunable magnetic properties.

  • 42. Glans, P. -A
    et al.
    Learmonth, T.
    Smith, K. E.
    Ferro, S.
    De Battisti, A.
    Mattesini, M.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Guo, J. -H
    Electronic structure of boron doped diamond: An x-ray spectroscopic study2013In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 102, no 16, p. 162103-Article in journal (Refereed)
    Abstract [en]

    The valence and conduction band electronic structure of boron-doped diamond has been measured using soft x-ray emission and absorption spectroscopy. The experimental results reveal p-type doping in the diamond film through the appearance of states in the band-gap. Structure distortion was observed around the doping center, while the long range order of the diamond structure remains. A chemically shifted C 1s level explains why one of the absorption features seems to appear below the valence band maximum. An excitonic feature was observed in the boron-doped diamond, similar to that observed in pure diamond, indicating that the exciton binding energy remains the same upon B-doping. 

  • 43. Gonzalez-Borrero, P. P.
    et al.
    Sato, F.
    Medina, A. N.
    Baesso, M. L.
    Bento, A. C.
    Baldissera, G.
    Persson, C.
    Niklasson, Gunnar A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, Claes Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    da Silva, A. Ferreira
    Optical band-gap determination of nanostructured WO3 film2010In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 96, no 6, p. 061909-Article in journal (Refereed)
    Abstract [en]

    The optical band-gap energy of a nanostructured tungsten trioxide film is determined using the photoacoustic spectroscopy method under continuous light excitation. The mechanism of the photoacoustic signal generation is discussed. The band-gap energy is also computed by other methods. The absorption coefficient as well as the band-gap energy of three different crystal structures of tungsten trioxide is calculated by a first-principles Green's function approach using the projector augmented wave method. The theoretical study indicates that the cubic crystal structure shows good agreement with the experimental data.

  • 44.
    Grechnev, Alexei
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Li, Sa
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Wilhelmsson, Ola
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Layered compound Nb3SiC2 predicted from first-principles theory2004In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 85, no 15, p. 3071-3073Article in journal (Refereed)
    Abstract [en]

    A previously unobserved ternary carbide, Nb3SiC2, belonging to the family of the so-called Mn+1AXn or MAX phases is predicted from first-principles calculations. It has a theoretical bulk modulus of 296 Gpa, wich is much higher than that of Ti3SiC2. The new phase is metastable with a formation energy of +0.02 eV/atom. We suggest that the phase may possibly be synthesized using thin film technology. The chemical binding of Nb3SiC2 is investigated using the balanced crystal orbital overlap population indicator and it is found to be dominated by the formation of Nb4D-C 2p covalent bonds.

  • 45.
    Gråsjö, Johan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Welch, Ken
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Strömme, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Determining the static dielectric permittivity of ion conducting materials2008In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 93, no 9, p. 092901-1Article in journal (Refereed)
    Abstract [en]

    A method is derived for the determination of the static dielectric permittivity of ion conducting materials when this parameter is obscured by electrode polarization in as-recorded low frequency dielectric spectra. The method requires permittivity measurements at two different electrode separations, and is applicable when the electric fields created by charge separation near the electrode surfaces do not induce nonlinear effects in the frequency region where electrode polarization begins to affect the dielectric response. The performance of the method is illustrated by the analysis of an ion conducting cellulose gel biosynthesized by the Acetobacter. xylinum bacterium. The method opens up possibilities to obtain more detailed information about dynamic processes in ion conducting materials from dielectric spectroscopy.

  • 46. Gütay, Levent
    et al.
    Regesch, David
    Larsen, Jes K
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Aida, Yasuhiro
    Depredurand, Valérie
    Siebentritt, Susanne
    Influence of copper excess on the absorber quality of CuInSe22011In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 99, no 15, p. 151912-Article in journal (Refereed)
  • 47. Haferman, H.
    et al.
    Brucas, R.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Soroka, Inna
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Katsnelson, M. I.
    Iusan, Diana
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Sanyal, B.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Hjörvarsson, Björgvin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Competing anisotropies in bcc Fe81Ni19/Co(001) superlattices2009In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 94, no 7, p. 073102-073102-3Article in journal (Refereed)
    Abstract [en]

    Amagnetization reorientation transition has been observed in Fe81Ni19/Co(001) superlattices bymeans of magneto-optical Kerr effect and magnetic force microscopy measurements.The transition is driven by the variation of the interfacedensity. First-principles calculations are combined with a linear stability analysisof the Landau–Lifshitz equation to clarify the mechanism that drivesthe transition. We are able to identify it as beingdriven by competing interface in-plane and uniaxial bulk out-of-plane anisotropies.The origin of the bulk anisotropy is attributed to tetragonaldistortions experimentally observed in these superlattices.

  • 48.
    Hammersberg, Johan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Majdi, Saman
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Kovi, Kiran Kumar
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Suntornwipat, Nattakarn
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Gabrysch, Markus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Twitchen, D. J.
    Isberg, Jan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Stability of polarized states for diamond valleytronics2014In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 104, no 23, p. 232105-Article in journal (Refereed)
    Abstract [en]

    The stability of valley polarized electron states is crucial for the development of valleytronics. A long relaxation time of the valley polarization is required to enable operations to be performed on the polarized states. Here, we investigate the stability of valley polarized states in diamond, expressed as relaxation time. We have found that the stability of the states can be extremely long when we consider the electron-phonon scattering processes allowed by symmetry considerations. We determine electron-phonon coupling constants by Time-of-Flight measurements and Monte Carlo simulations and use these data to map out the relaxation time temperature dependency. The relaxation time for diamond can be microseconds or longer below 100 K and 100 V/cm due to the strong covalent bond, which is highly encouraging for future use in valleytronic applications. (C) 2014 AIP Publishing LLC.

  • 49. Hau-Riege, S. P.
    et al.
    London, R. A.
    Bionta, R. M.
    McKernan, M. A.
    Baker, S. L.
    Krzywinski, J.
    Sobierajski, R.
    Nietubyc, R.
    Pelka, J. B.
    Jurek, M.
    Juha, L.
    Chalupsky, J.
    Cihelka, J.
    Hajkova, V.
    Velyhan, A.
    Krasa, J.
    Kuba, J.
    Tiedtke, K.
    Toleikis, S.
    Tschentscher, Th.
    Wabnitz, H.
    Bergh, Magnus
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology.
    Caleman, Carl
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology.
    Sokolowski-Tinten, K.
    Stojanovic, N.
    Zastrau, U.
    Damage threshold of inorganic solids under free-electron-laser irradiation at 32.5 nm wavelength2007In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 90, no 17, p. 173128-Article in journal (Refereed)
    Abstract [en]

    Samples of B4C, amorphous C, chemical-vapor-deposition-diamond C, Si, and SiC were exposed to single 25 fs long pulses of 32.5 nm free-electron-laser radiation at fluences of up to 2.2 J/cm(2). The samples were chosen as candidate materials for x-ray free-electron-laser optics. It was found that the threshold for surface damage is on the order of the fluence required for thermal melting. For larger fluences, the crater depths correspond to temperatures on the order of the critical temperature, suggesting that the craters are formed by two-phase vaporization.

  • 50. Hau-Riege, S. P.
    et al.
    London, R. A.
    Bionta, R. M.
    Ryutov, D.
    Soufli, R.
    Bajt, S.
    McKernan, M. A.
    Baker, S. L.
    Krzywinski, J.
    Sobierajski, R.
    Nietubyc, R.
    Klinger, D.
    Pelka, J. B.
    Jurek, M.
    Juha, L.
    Chalupsky, J.
    Cihelka, J.
    Hajkova, V.
    Velyhan, A.
    Krasa, J.
    Tiedtke, K.
    Toleikis, S.
    Wabnitz, H.
    Bergh, M.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Molecular biophysics.
    Caleman, C.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Molecular biophysics.
    Timneanu, N.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Molecular biophysics.
    Wavelength dependence of the damage threshold of inorganic materials under extreme-ultraviolet free-electron-laser irradiation2009In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 95, no 11, p. 111104-111104-3Article in journal (Refereed)
    Abstract [en]

    We exposed bulk SiC and films of SiC and B4C to single 25 fs long free-electron-laser pulses with wavelengths between 13.5 and 32 nm. The materials are candidates for x-ray free-electron laser optics. We found that the threshold for surface-damage of the bulk SiC samples exceeds the fluence required for thermal melting at all wavelengths. The damage threshold of the film sample shows a strong wavelength dependence. For wavelengths of 13.5 and 21.7 nm, the damage threshold is equal to or exceeds the melting threshold, whereas at 32 nm the damage threshold falls below the melting threshold.

12345 1 - 50 of 201
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