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  • 551.
    Werheit, H.
    et al.
    Univ Duisburg Essen, Expt Phys, D-47048 Duisburg, Germany.
    Flachbart, K.
    Slovak Acad Sci, Inst Expt Phys, Kosice 04001, Slovakia.
    Pristas, G.
    Slovak Acad Sci, Inst Expt Phys, Kosice 04001, Slovakia.
    Lotnyk, D.
    Safarik Univ, Inst Phys, Fac Sci, Kosice 04001, Slovakia.
    Filipov, V.
    IN Frantsevich Inst Problems Mat Sci NASU, UA-03142 Kiev, Ukraine.
    Kuhlmann, U.
    Univ Duisburg Essen, Expt Phys, D-47048 Duisburg, Germany;Pirelli Deutschland GmbH, Hochster Str 48-60, D-64747 Breuberg, Germany.
    Shitsevalova, N.
    IN Frantsevich Inst Problems Mat Sci NASU, UA-03142 Kiev, Ukraine.
    Lundström, Torsten
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Influence of dopants, particularly carbon, on beta-rhombohedral boron2017In: Semiconductor Science and Technology, ISSN 0268-1242, E-ISSN 1361-6641, Vol. 32, no 9, article id 095015Article in journal (Refereed)
    Abstract [en]

    Due to the high affinity of carbon to boron, the preparation of carbon-free boron is problematic. Even high-purity (6N) beta-rhombohedral boron contains 30-60 ppm of C. Hence, carbon affects the boron physical properties published so far more or less significantly. We studied well-defined carbon-doped boron samples based on pure starting material carefully annealed with up to about 1% C, thus assuring homogeneity. We present and discuss their electrical conductivity, optical absorption, luminescence and phonon spectra. Earlier attempts of other authors to determine the conductivity of C-doped boron are revised. Our results allow estimating the effects of oxygen and iron doping on the electrical conductivity using results taken from literature. Discontinuities at low T impair the electronic properties.

  • 552.
    Werwinski, Miroslaw
    et al.
    Polish Acad Sci, Inst Mol Phys, M Smoluchowskiego 17, PL-60179 Poznan, Poland.
    Edstroem, Alexander
    Swiss Fed Inst Technol, Mat Theory, Wolfgang Pauli Str 27, CH-8093 Zurich, Switzerland.
    Rusz, Jan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Hedlund, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Gunnarsson, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Svedlindh, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Cedervall, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Magnetocrystalline anisotropy of Fe5PB2 and its alloys with Co and 5d elements: A combined first-principles and experimental study2018In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 98, no 21, article id 214431Article in journal (Refereed)
    Abstract [en]

    The Fe5PB2 compound offers tunable magnetic properties via the possibility of various combinations of substitutions on the Fe and P sites. Here, we present a combined computational and experimental study of the magnetic properties of (Fe1-xCox)(5)PB2. Computationally, we are able to explore the full concentration range, while the real samples were only obtained for 0 <= x <= 0.7. The calculated magnetic moments, Curie temperatures, and magnetocrystalline anisotropy energies (MAEs) are found to decrease with increasing Co concentration. Co substitution allows for tuning the Curie temperature in a wide range of values, from about six hundred to zero kelvins. As the MAE depends on the electronic structure in the vicinity of the Fermi energy, the geometry of the Fermi surface of Fe5PB2 and the k-resolved contributions to the MAE are discussed. Low-temperature measurements of an effective anisotropy constant for a series of (Fe1-xCox)(5)PB2 samples determined the highest value of 0.94 MJ m(-3) for the terminal Fe5PB2 composition, which then decreases with increasing Co concentration, thus confirming the computational result that Co alloying of Fe5PB2 is not a good strategy to increase the MAE of the system. However, the relativistic version of the fixed spin moment method reveals that a reduction in the magnetic moment of Fe5PB2, by about 25%, produces a fourfold increase of the MAE. Furthermore, calculations for (Fe0.95X0.05)(5)PB2 (X = 5d element) indicate that 5% doping of Fe5PB2 with W or Re should double the MAE. These are results of high interest for, e.g., permanent magnet applications, where a large MAE is crucial.

  • 553.
    Werwinski, Miroslaw
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Polish Acad Sci, Inst Mol Phys, Ul M Smoluchowskiego 17, PL-60179 Poznan, Poland..
    Kontos, Sofia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Gunnarsson, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Svedlindh, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Cedervall, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Höglin, Viktor
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Edström, Alexander
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Rusz, Jan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Magnetic properties of Fe5SiB2 and its alloys with P, S, and Co2016In: PHYSICAL REVIEW B, ISSN 2469-9950, Vol. 93, no 17, article id 174412Article in journal (Refereed)
    Abstract [en]

    Fe5SiB2 has been synthesized and magnetic measurements have been carried out, revealing that M-sat = 0.92 MA/mat T = 300 K. The M versus T curve shows a broad peak around T = 160 K. The anisotropy constant K-1, estimated at T = 300 K, is 0.25 MJ/m(3). Theoretical analysis of Fe5SiB2 system has been carried out and extended to the full range of Fe5Si1-xPxB2, Fe5P1-xSxB2, and (Fe1-xCox)(5)SiB2 compositions. The electronic band structures have been calculated using the full-potential local-orbital minimum-basis scheme (FPLO-14). The calculated total magnetic moments are 9.20, 9.15, 9.59, and 2.42 mu(B) per formula units of Fe5SiB2, Fe5PB2, Fe5SB2, and Co5SiB2, respectively. In agreement with experiment, magnetocrystalline anisotropy energies (MAE's) calculated for T = 0 K change from a negative (easy-plane) anisotropy -0.28 MJ/m(3) for Fe5SiB2 to the positive (easy-axis) anisotropy 0.35 MJ/m(3) for Fe5PB2. Further increase of the number of p electrons in Fe5P1-xSxB2 leads to an increase of MAE up to 0.77 MJ/m(3) for the hypothetical Fe5P0.4S0.6B2 composition. Volume variation and fixed spin moment calculations (FSM) performed for Fe5SiB2 show an inverse relation between MAE and magnetic moment in the region down to about 15% reduction of the spin moment. The alloying of Fe5SiB2 with Co is proposed as a practical realization of magnetic moment reduction, which ought to increase MAE. MAE calculated in virtual crystal approximation (VCA) for a full range of (Fe1-xCox)(5)SiB2 compositions reaches the maximum value of 1.16 MJ/m(3) at Co concentration x = 0.3, with the magnetic moment 7.75 mu(B) per formula unit. Thus, (Fe0.7Co0.3)(5)SiB2 is suggested as a candidate for a rare-earth free permanent magnet. For the stoichiometric Co5SiB2 there is an easy-plane magnetization, with the value of MAE = -0.15 MJ/m(3).

  • 554.
    Widenkvist, Erika
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Yang, Wenzhi
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Physical Organic Chemistry.
    Akhtar, Sultan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences.
    Palmgren, Pål
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Knut, Ronny
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Karis, Olof
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Grennberg, Helena
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Physical Organic Chemistry.
    Graphene Formation by Sonochemical Exfoliation of Bromine-intercalated Graphite.Influence of Solvent Properties on Exfoliation Yield and Deposition OutcomeManuscript (preprint) (Other academic)
  • 555.
    Wikberg, J. M.
    et al.
    Radboud Univ Nijmegen, Inst Mol & Mat, NL-6525 AJ Nijmegen, Netherlands..
    Razdolski, I.
    Radboud Univ Nijmegen, Inst Mol & Mat, NL-6525 AJ Nijmegen, Netherlands..
    Kirilyuk, A.
    Radboud Univ Nijmegen, Inst Mol & Mat, NL-6525 AJ Nijmegen, Netherlands..
    Rasing, Th.
    Radboud Univ Nijmegen, Inst Mol & Mat, NL-6525 AJ Nijmegen, Netherlands..
    Sadowski, J.
    Lund Univ, MAX Lab, SE-22100 Lund, Sweden..
    Ottosson, Mikael
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Wei, Y.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Svedlindh, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Evolving magnetization dynamics in Mn3-xGa2015In: Ultrafast Magnetism I / [ed] Bigot, JY; Hubner, W; Rasing, T; Chantrell, R, 2015, p. 23-25Conference paper (Refereed)
  • 556.
    Williams, Kirk
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Köhler, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Boman, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Fabrication and Mechanical Characterization of LCVD-Deposited Carbon Micro-Springs2006In: Sensors and Actuators A-Physical, ISSN 0924-4247, E-ISSN 1873-3069, Vol. 130-131, p. 358-364Article in journal (Refereed)
    Abstract [en]

    Carbon micro-springs were fabricated using laser-assisted chemical vapor deposition (LCVD) at laser powers and ethylene pressures ranging between 200 and 700 mW and 400 and 900 mbar, respectively. A scanning electron microscope was used to determine geometrical parameters such as wire diameter, outside coil diameter, spacing, and pitch. The spring rates for nine batches of springs – chosen from the extremes and middle of the processing ranges – were determined with values ranging between 0.0294 and 0.0604 mN/ m. With the spring rate values, trends regarding the shear modulus and the modulus elasticity of the carbon material as a function of laser power and precursor pressure were deduced. The shear moduli of the chosen batches had values between 13.6 and 733.5 MPa, and using a Poisson’s ratio value of 0.3 the moduli of elasticity ranged from 0.0353 to 1.9071 MPa.

  • 557.
    Xu, Chao
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Renault, Stevén
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Ebadi, Mahsa
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Wang, Zhaohui
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Björklund, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Guyomard, Dominique
    Univ Nantes, CNRS, UMR 6502, Inst Mat Jean Rouxel IMN, F-44322 Nantes 3, France..
    Brandell, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Edström, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Gustafsson, Torbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    LiTDI: A Highly Efficient Additive for Electrolyte Stabilization in Lithium-Ion Batteries2017In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 29, no 5, p. 2254-2263Article in journal (Refereed)
    Abstract [en]

    The poor stability of LiPF6-based electrolytes has always been a bottleneck for conventional lithium-ion batteries. The presence of inevitable trace amounts of moisture and the operation of batteries at elevated temperatures are particularly detrimental to electrolyte stability. Here, lithium 2trifluoromethy1-4,5-dicyanoimidazole (LiTDI) is investigated as a moisture-scavenging electrolyte additive and can sufficiently suppress the hydrolysis of LiPF6. With 2 wt % LiTDI, no LiPF6 degradation can be detected after storage for 35 days, even though the water level in the electrolyte is enriched by 2000 ppm. An improved thermal stability is also obtained by employing the LiTDI additive, and the moisture-scavenging mechanism is discussed. The beneficial effects of the LiTDI additive on battery performance are demonstrated by the enhanced capacity retention of both the LiNi1/3Mn1/3Co1/3O2 (NMC)/Li and NMC/graphite cells at 55 degrees C. In particular, the increase in cell voltage hysteresis is greatly hindered when LiTDI is presented in the electrolyte. Further development of the LiTDI additive may allow the improvement of elevated-temperature batteries, as well as energy savings by reducing the amount of effort necessary for dehydration of battery components.

  • 558.
    Xu, Xingxing
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Makaraviciute, Asta
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Pettersson, Jean
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Zhang, Shi-Li
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Nyholm, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Zhang, Zhen
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Revisiting the factors influencing gold electrodes prepared using cyclic voltammetry2019In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 283, p. 146-153Article in journal (Refereed)
    Abstract [en]

    Gold is widely used as the electrode material in different chemi- and biosensing applications while cyclic voltammetry (CV) in sulfuric acid solutions is a commonly employed method for gold surface preparation and characterization. However, as shown herein, chloride leakage from the Ag/AgCl/sat. KCl reference electrode and platinum dissolution from the platinum counter electrode can severely compromise the reproducibility and hence the reliability of the prepared gold electrodes. The aim of this work is to obtain a comprehensive understanding of the separate and interdependent effects of the aforementioned factors on the voltammetric behavior of microfabricated polycrystalline gold electrodes. It is shown that the leakage of chloride gives rise to etching of both the gold working and the platinum counter electrodes and that the chloride concentration has a strong influence on the ratio between the obtained gold and platinum concentrations in the electrolyte. The dissolved gold and platinum are then re-deposited on the gold electrode on the cathodic voltammetric scan, changing the structure and properties of the electrode. It is also demonstrated that the changes in the properties of the gold electrode are determined by the ratio between the co-deposited platinum and gold rather than the absolute amount of platinum deposited on the gold electrode. In addition, the chloride and sulfate adsorption behavior on the gold electrode is carefully investigated. It is proposed that redox peaks due to the formation ofthe corresponding Au(I) complexes can be seen in the double layer region of the voltammogram. The results show that the chloride leakage from the reference electrode needs to be carefully controlled and that platinum counter electrodes should be avoided when developing gold sensing electrodes. The present comprehensive understanding of the electrochemical performance of gold electrodes prepared using CV should be of significant importance in conjunction with both fundamental investigations and practical applications.

  • 559.
    Yakimova, R.
    et al.
    Linkoping Univ, Linkoping, Sweden.
    Virojanadara, C.
    Linkoping Univ, Linkoping, Sweden.
    Gogova, D.
    Leibniz Inst Crystal Growth, Berlin, Germany.
    Syväjärvi, M.
    Linkoping Univ, Linkoping, Sweden.
    Siche, Dietmar
    Leibniz Inst Crystal Growth, Berlin, Germany.
    Larsson, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Johansson, Leif I.
    Linkoping Univ, Linkoping, Sweden.
    Analysis of the Formation Conditions for Large Area Epitaxial Graphene on SiC Substrates2009In: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 565, p. 645-648Article in journal (Refereed)
  • 560.
    Yang, Lei
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry. Xian Univ Architecture & Technol, Sch Environm & Municipal Engn, Xian 710055, Shaanxi, Peoples R China.
    Schölin, Rebecka
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Gabrielsson, Erik
    Royal Inst Technol, Sch Chem Sci & Engn, Organ Chem, S-11428 Stockholm, Sweden.
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Sun, Licheng
    Xian Univ Architecture & Technol, Sch Environm & Municipal Engn, Xian 710055, Shaanxi, Peoples R China.
    Hagfeldt, Anders
    Swiss Fed Inst Technol, Dept Chem & Chem Engn, Lab Photomol Sci, Stn 6, CH-1015 Lausanne, Switzerland.
    Edvinsson, Tomas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Johansson, Erik M. J.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Experimental and Theoretical Investigation of the Function of 4-tert-Butyl Pyridine for Interface Energy Level Adjustment in Efficient Solid-State Dye-Sensitized Solar Cells2018In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 10, no 14, p. 11572-11579Article in journal (Refereed)
    Abstract [en]

    4-tert-Butylpyridine (t-BP) is commonly used in solid state dye-sensitized solar cells (ssDSSCs) to increase the photovoltaic performance. In this report, the mechanism how t-BP functions as a favorable additive is investigated comprehensively. ssDSSCs were prepared with different concentrations of t-BP, and a clear increase in efficiency was observed up to a maximum concentration and for higher concentrations the efficiency thereafter decreases. The energy level alignment in the complete devices was measured using hard X-ray photoelectron spectroscopy (HAXPES). The results show that the energy levels of titanium dioxide are shifted further away from the energy levels of spiro-OMeTAD as the t-BP concentration is increased. This explains the higher photovoltage obtained in the devices with higher t-BP concentration. In addition, the electron lifetime was measured for the devices and the electron lifetime was increased when adding t-BP, which can be explained by the recombination blocking effect at the surface of TiO2. The results from the HAXPES measurements agree with those obtained from density functional theory calculations and give an understanding of the mechanism for the improvement, which is an important step for the future development of solar cells including t-BP.

  • 561.
    Zhao, Jie
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Pan, Ruijun
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Sun, Rui
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Wen, Chenyu
    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.
    Wu, Biao
    Nyholm, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Zhang, Zhi-Bin
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    High-Conductivity Reduced-Graphene-Oxide/Copper Aerogel for Energy Storage2019In: Nano Energy, ISSN 2211-2855, E-ISSN 2211-3282, Vol. 60, p. 760-767Article in journal (Refereed)
    Abstract [en]

    This work reports a room-temperature, solution-phase and one-pot method for macro-assembly of a three-dimensional (3D) reduced-graphene-oxide/copper hybrid hydrogel. The hydrogel is subsequently transformed into a highly conductive aerogel via freeze-drying. The aerogel, featuring reduced graphene oxide (rGO) networks decorated with Cu and CuxO nanoparticles (Cu/CuxO@rGO), exhibits a specific surface area of 48 m(2)/g and an apparent electrical conductivity of similar to 33 and similar to 430 S/m prior to and after mechanical compression, respectively. The compressed Cu/CuxO@rGO aerogel delivers a specific capacity of similar to 453 mAh g(-1) at a current density of 1 A/g and similar to 184 mAh g(-1) at 50 A/g in a 3 M KOH aqueous electrolyte evidenced by electrochemical measurements. Galvanostatic cycling tests at 5 A/g demonstrates that the Cu/CuxO@rGO aerogel retains 38% (similar to 129 mAh g(-1)) of the initial capacity (similar to 339 mAh g(-1)) after 500 cycles. The straightforward manufacturing process and the promising electrochemical performances make the Cu/CuxO@rGO aerogel an attractive electrode candidate in energy storage applications.

  • 562.
    Zhao, Shuainan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry. Department of Chemistry - Ångström Laboratory.
    Theoretical Studies of Diamond for Electronic Applications2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Diamond has since many years been applied in electronic fields due to its extraordinary properties. Substitutional dopants and surface functionalization have also been introduced in order to improve the electrochemical properties. However, the basic mechanism at an atomic level, regarding the effects of dopants and terminations, is still under debate. In addition, theoretical modelling has during the last decades been widely used for the interpretation of experimental results, prediction of material properties, and for the guidance of future materials. Therefore, the purpose of this research project has been to theoretically investigate the influence of dopants and adsorbates on electronic and geometrical structures by using density functional theory (DFT) under periodic boundary conditions.

    Both the global and local effects of dopants (boron and phosphorous) and terminations have been studied. The models have included H-, OH-, F-, Oontop-, Obridge- and NH2-terminations on the diamond surfaces. For all terminating species studied, both boron and phosphorous have been found to show a local impact, instead of a global one, on diamond structural geometry and electronic properties. Therefore, the terminating species only affect the DOS of the surface carbon layers. In addition, Oontop-terminated (111) diamond surfaces present reactive surface properties and display metallic conductivity. Moreover, the conductivity of the diamond surface can be dramatically increased by the introduction of a phosphorous dopant in the lattice. The work function of a diamond surface has also been found to be influenced to a large extent by the various adsorbates and the dopant levels.

    Diamond can also be used as a promising substrate for an epitaxial graphene adlayer. The effects of dopants and terminations on the graphene and diamond (111) interfacial systems have been investigated theoretically in great detail. The interfacial interaction is of the Van der Waal type with an interfacial distance around 3 Å. The interactions between graphene and a terminated diamond substrate were found to be relatively weaker than those for a non-terminated diamond substrate (even with dopants). For all interface systems between graphene and diamond, a diamond-supported graphene adlayer without induced defects can still keep its intrinsic high carrier mobility. A minor charge transfer was observed to take place from the graphene adlayer to a non-terminated diamond substrate (with or without dopants) and to Oontop-, OH- or Obridge-terminated diamond substrates. However, for the situation with an H-terminated diamond surface, the electron transfer took place from the diamond surface to graphene. On the contrary, an interfacial system with a non-terminated diamond surface offers a more pronounced charge transfer than that of the terminated diamond substrates. A small finite band gap at the Dirac point was also observed for the Oontop-terminated diamond-supporting graphene adlayer.

     

     

     

    List of papers
    1. A Theoretical Study of the Energetic Stability and Geometry of Terminated and B-Doped Diamond (111) Surfaces
    Open this publication in new window or tab >>A Theoretical Study of the Energetic Stability and Geometry of Terminated and B-Doped Diamond (111) Surfaces
    2014 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 118, no 4, p. 1944-1957Article in journal (Refereed) Published
    Abstract [en]

    The effect of B doping on the surface (111) reactivity has, in the present study, been investigated for various surface terminations, H, OH, Oon-top and F. This type of surface modification has experimentally been proven to be extremely important for, for example, applications based on surface electrochemistry. Density functional theory (DFT) has here been used to study both the local and more global effects of substitutionally positioned B atoms in the upper part of the diamond (111) surface. For this purpose, adsorption energies for the various terminating species have been calculated, and the observed results have been carefully analyzed in order to gain a deeper knowledge about the atomic-level cause of the observed effects. As a result, the B dopant shows a clear, but local, effect for all terminating species investigated. In addition, it is only the radical O-terminating species that show a special and high reactivity on the diamond surface. The other terminating species show a much lower reactivity, which in addition are very similar.

    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:uu:diva-220298 (URN)10.1021/jp409278x (DOI)000330610200023 ()
    Available from: 2014-03-17 Created: 2014-03-12 Last updated: 2017-12-05
    2. A Theoretical Study of the Energetic Stability and Electronic Structure of Terminated and P-doped Diamond (100)-2x1 Surfaces
    Open this publication in new window or tab >>A Theoretical Study of the Energetic Stability and Electronic Structure of Terminated and P-doped Diamond (100)-2x1 Surfaces
    (English)Manuscript (preprint) (Other academic)
    National Category
    Inorganic Chemistry
    Identifiers
    urn:nbn:se:uu:diva-283407 (URN)
    Available from: 2016-04-12 Created: 2016-04-12 Last updated: 2016-06-01Bibliographically approved
    3. First principle study of the attachment of graphene onto non-doped and doped diamond (111)
    Open this publication in new window or tab >>First principle study of the attachment of graphene onto non-doped and doped diamond (111)
    2016 (English)In: Diamond and related materials, ISSN 0925-9635, E-ISSN 1879-0062, Vol. 66, p. 52-60Article in journal (Refereed) Published
    Abstract [en]

    Density function theory (DFT) calculations have in the present study been used to study the adhesion of a graphene monolayer onto a non-, B-, or N-doped diamond (111) surface. Semiempirical dispersion corrections were used to take the Van-der-Waals corrections into consideration. In case of non-doped diamond as a substrate, DFT calculations (based on the local density approximation (LDA)) have shown a strong binding between graphene and the diamond (111) surface at a shorter distance (2.47 Å). The binding energy was − 14.5 kJ/mol per Cgraphene atom. In comparison, the generalized gradient spin density approximation (GG(S)A) was found to predict a weaker (− 9.6 kJ/mol) interfacial bond at a distance of 3.10 Å. For the situation with B-, or N-, doped diamond, the optimized shorter diamond-graphene distance was found to be 3.01 and 3.24 Å, respectively. The corresponding adhesion energies per Cgraphene atom was − 9.9 kJ/mol (B-doping) and − 9.6 kJ/mol (N-doping), which are quite similar to the non-doped situation (− 9.6 kJ/mol). For all situations in the present study, the graphene layer was found to remain its aromatic character. However, a minor charge transfer was observed to take place from the graphene adlayer towards the non-doped and doped diamond (111) substrates.

    Keywords
    Density functional theory; Epitaxial graphene; Diamond substrate; Charge transfer
    National Category
    Inorganic Chemistry
    Research subject
    Chemistry with specialization in Inorganic Chemistry
    Identifiers
    urn:nbn:se:uu:diva-283287 (URN)10.1016/j.diamond.2016.03.017 (DOI)000379633000007 ()
    Funder
    Swedish Research Council, VR 2012-4107
    Available from: 2016-04-12 Created: 2016-04-12 Last updated: 2017-11-30Bibliographically approved
    4. Theoretical Study of the Attachment of Graphene onto Different Terminated Diamond (111)
    Open this publication in new window or tab >>Theoretical Study of the Attachment of Graphene onto Different Terminated Diamond (111)
    (English)Article in journal (Refereed) Submitted
    Abstract [en]

    Density functional theory (DFT) calculations have in the present study been used to study the adhesion of a graphene monolayer onto a different (H-, F-, Oontop-, OH- and Obri-) terminated, or 2x1- reconstructed, diamond (111) surface. The generalized gradient spin density approximation (GG(S)A) with the semi-empirical dispersion corrections(PBE-TS)were used in the study of the Van-der-Waals interactions. There is a weaker interfacial bond (only of type Wan-der-Waals interaction) at a distance around 3 Å (from 2.68 to 3.36 Å) for the interfacial graphene//diamond systems in the present study. The H-terminated diamond (111) surface provided the largest interaction (smallest adsorption energy: -10.6 eV) with the graphene ad-layer and in contrast, the F adsorbates provided the smallest interaction (largest adsorption energy: -2.9 eV). For all situations in the present study, the graphene layer was found to remain its aromatic character. However, there is an observed electron transfer between the graphene adlayer and the H-, Oontop- , Obri-, or OH- terminated diamond substrates. Moreover, the Oontop-terminated diamond-supported graphene shows a finite band gap.

    National Category
    Inorganic Chemistry
    Identifiers
    urn:nbn:se:uu:diva-283404 (URN)
    Available from: 2016-04-12 Created: 2016-04-12 Last updated: 2016-06-01Bibliographically approved
  • 563.
    Zhao, Shuainan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Larsson, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    A Theoretical Study of the Energetic Stability and Geometry of Terminated and B-Doped Diamond (111) Surfaces2014In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 118, no 4, p. 1944-1957Article in journal (Refereed)
    Abstract [en]

    The effect of B doping on the surface (111) reactivity has, in the present study, been investigated for various surface terminations, H, OH, Oon-top and F. This type of surface modification has experimentally been proven to be extremely important for, for example, applications based on surface electrochemistry. Density functional theory (DFT) has here been used to study both the local and more global effects of substitutionally positioned B atoms in the upper part of the diamond (111) surface. For this purpose, adsorption energies for the various terminating species have been calculated, and the observed results have been carefully analyzed in order to gain a deeper knowledge about the atomic-level cause of the observed effects. As a result, the B dopant shows a clear, but local, effect for all terminating species investigated. In addition, it is only the radical O-terminating species that show a special and high reactivity on the diamond surface. The other terminating species show a much lower reactivity, which in addition are very similar.

  • 564.
    Zhao, Shuainan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Larsson, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry. Uppsala Univ, Dept Chem, Angstrom Lab, Uppsala, Sweden.
    First Principle Study of the Attachment of Graphene onto Different Terminated Diamond (111) Surfaces2019In: Advances in Condensed Matter Physics, ISSN 1687-8108, E-ISSN 1687-8124, article id 9098256Article in journal (Refereed)
    Abstract [en]

    The adhesion of a graphene monolayer onto terminated or 2x1-reconstructed diamond (111) surfaces has in the present study been theoretically investigated by using a Density Functional Theory (DFT) method. H, F, O, and OH species were used for the surface termination. The generalized gradient spin density approximation (GG(S)A) with the semiempirical dispersion corrections were used in the study of the Van der Waals interactions. There is a weaker interfacial bond (only of type Wan-der-Waals interaction) at a distance around 3 angstrom (from 2.68 to 3.36 angstrom ) for the interfacial graphene//diamond systems in the present study. The strongest binding of graphene was obtained for the H-terminated surface, with an adhesion energy of -10.6 eV. In contrast, the weakest binding of graphene was obtained for F-termination (with an adhesion energy of -2.9 eV). For all situations in the present study, the graphene layer was found to retain its aromatic character. In spite of this, a certain degree of electron transfer was observed to take place from graphene to Oontop-, Obridge-, and OH-terminated diamond surface. In addition, graphene attached to Oontop-terminated surface showed a finite band gap.

  • 565.
    Zhou, Shengyang
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Nyholm, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Strømme, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Wang, Zhaohui
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Cladophora Cellulose: Unique Biopolymer Nanofibrils for Emerging Energy, Environmental, and Life Science Applications2019In: Accounts of Chemical Research, ISSN 0001-4842, E-ISSN 1520-4898, Vol. 52, no 8, p. 2232-2243Article, review/survey (Refereed)
    Abstract [en]

    Conspectus

    Because of its natural abundance, hierarchical fibrous structure, mechanical flexibility, potential for chemical modification, biocompatibility, renewability, and abundance, cellulose is one of the most promising green materials for a bio-based future and sustainable economy. Cellulose derived from wood or bacteria has dominated the industrial cellulose market and has been developed to produce a number of advanced materials for applications in energy storage, environmental, and biotechnology areas. However, Cladophora cellulose (CC) extracted from green algae has unprecedented advantages over those celluloses because of its high crystallinity (>95%), low moisture adsorption capacity, excellent solution processability, high porosity in the mesoporous range, and associated high specific surface area. The unique physical and chemical properties of CC can add new features to and enhance the performance of nanocellulose-based materials, and these attributes have attracted a great deal of research interest over the past decade.This Account summarizes our recent research on the preparation, characterization, functionalization, and versatile applications of CC. Our aim is to provide a comprehensive overview of the uniqueness of CC with respect to material structure, properties, and emerging applications. We discuss the potential of CC in energy storage, environmental science, and life science, with emphasis on applications in which its properties are superior to those of other nanocellulose forms. Specifically, we discuss the production of the first-ever paper battery based on CC. This battery has initiated a rising interest in the development of sustainable paper-based energy storage devices, where cellulose is used as a combined building block and binder for paper electrodes of various types in combination with carbon, conducting polymers, and other electroactive materials. High-active-mass and high-mass-loading paper electrodes can be made in which the CC acts as a high-surface-area and porous substrate while a thin layer of electroactive material is coated on individual nanofibrils. We have shown that CC membranes can be used directly as battery separators because of their low moisture content, high mesoporosity, high thermal stability, and good electrolyte wettability. The safety, stability, and capacity of lithium-ion batteries can be enhanced simply by using CC-based separators. Moreover, the high chemical modifiability and adjustable porosity of dried CC papers allow them to be used as advanced membranes for environmental science (water and air purification, pollutant adsorption) and life science (virus isolation, protein recovery, hemodialysis, DNA extraction, bioactive substrates). Finally, we outline some concluding perspectives on the challenges and future directions of CC research with the aim to open up yet unexplored fields of use for this interesting material.

  • 566.
    Zhu, Dechun
    et al.
    Department of Chemical and Materials Engineering, Hefei University, China.
    Mao, Fang
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Zhao, Shuxi
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    The influence of oxygen in TiAlOxNy on the optical properties of colored solar-absorbing coatings2012In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 98, p. 179-184Article in journal (Refereed)
    Abstract [en]

    Low cost and ease of fabrication are important factors for solar-thermal applications in energy-efficient buildings. This contribution reports the influence of oxygen on structure, optical properties and chromaticity of TiAlOxNy thin films prepared by DC magnetron sputtering. It is an extension of a previous study on colored solar-thermal absorbers based on titanium-aluminum nitride. The purpose is to investigate the possibility of using TiAlOxNy as middle layer to achieve a gradient effect. The results reveal that the structure and optical properties of the TiAlOxNy coatings are sensitive to the oxygen content under certain sputtering conditions.  The ratio of oxygen/nitrogen of 0.7:10 is the most appropriate to form the crystalline structure of TiAlON.  The optical constants of TiAlN and TiAlON were deduced by fitting the experimental data. It shows that both the refractive index (n) and the extinction coefficient (k) are decreased when oxygen is introduced to form titanium-aluminium nitro-oxide. The gradient effect can be achieved and controlled by adjusting the ratio of oxygen/nitrogen flow during the process to enhance solar absorptance while keeping the desired color appearance.

  • 567.
    Zichi, Julien
    et al.
    Royal Inst Technol KTH, Dept Appl Phys, SE-10691 Stockholm, Sweden.
    Chang, Jin
    Delft Univ Technol, Fac Appl Sci, ImPhys Dept, Opt Res Grp, Lorentzweg 1, NL-2628 CJ Delft, Netherlands.
    Steinhauer, Stephan
    Royal Inst Technol KTH, Dept Appl Phys, SE-10691 Stockholm, Sweden.
    Johansson, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Los, Johannes W. N.
    Single Quantum BV, NL-2628 CH Delft, Netherlands.
    Visser, Gus
    Single Quantum BV, NL-2628 CH Delft, Netherlands.
    Kalhor, Nima
    Single Quantum BV, NL-2628 CH Delft, Netherlands.
    Lettner, Thomas
    Royal Inst Technol KTH, Dept Appl Phys, SE-10691 Stockholm, Sweden.
    Elshaari, Ali W.
    Royal Inst Technol KTH, Dept Appl Phys, SE-10691 Stockholm, Sweden.
    Zadeh, Iman Esmaeil
    Delft Univ Technol, Fac Appl Sci, ImPhys Dept, Opt Res Grp, Lorentzweg 1, NL-2628 CJ Delft, Netherlands.
    Zwiller, Val
    Royal Inst Technol KTH, Dept Appl Phys, SE-10691 Stockholm, Sweden;Single Quantum BV, NL-2628 CH Delft, Netherlands.
    Optimizing the stoichiometry of ultrathin NbTiN films for high-performance superconducting nanowire single-photon detectors2019In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 27, no 19, p. 26579-26587Article in journal (Refereed)
    Abstract [en]

    The requirements in quantum optics experiments for high single-photon detection efficiency. low timing jitter, low dark count rate and short dead time have been fulfilled with the development of superconducting nanowire single-photon detectors. Although they offer a detection efficiency above 90%, achieving a high time resolution in devices made of amorphous materials is a challenge, particularly at temperatures above 0.8 K. Devices made from niobium nitride and niobium titanium nitride allow us to reach the best timing jitter but. in turn, have stronger requirements in terms of film quality to achieve a high efficiency. Here we take advantage of the flexibility of reactive co-sputter deposition to tailor the composition of NbxTi1-xN superconducting films and show that a Nb fraction of x = 0.62 allows for the fabrication of detectors from films as thick as 9 nm and covering an active area of 20 mu m. with a wide detection saturation plateau at telecom wavelengths and in particular at 1550 nm. This is a signature of an internal detection efficiency saturation, achieved while maintaining the high time resolution associated with NbTiN and operation at 2.5K. With our optimized recipe, we reliably fabricated detectors with high critical current densities reaching a saturation plateau at 1550 nm with 80% system detection efficiency and with a FWHM timing jitter as low as 19.5 ps. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

  • 568.
    Zlotea, C.
    et al.
    Univ Paris Est, Inst Chim & Mat Paris Est UMR7182, CNRS, UPEC, 2-8 Rue Henri Dunant, F-94320 Thiais, France.
    Sow, M. A.
    Univ Paris Est, Inst Chim & Mat Paris Est UMR7182, CNRS, UPEC, 2-8 Rue Henri Dunant, F-94320 Thiais, France.
    Ek, Gustav
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Couzinie, J-P
    Univ Paris Est, Inst Chim & Mat Paris Est UMR7182, CNRS, UPEC, 2-8 Rue Henri Dunant, F-94320 Thiais, France.
    Perriere, L.
    Univ Paris Est, Inst Chim & Mat Paris Est UMR7182, CNRS, UPEC, 2-8 Rue Henri Dunant, F-94320 Thiais, France.
    Guillot, I
    Univ Paris Est, Inst Chim & Mat Paris Est UMR7182, CNRS, UPEC, 2-8 Rue Henri Dunant, F-94320 Thiais, France.
    Bourgon, J.
    Univ Paris Est, Inst Chim & Mat Paris Est UMR7182, CNRS, UPEC, 2-8 Rue Henri Dunant, F-94320 Thiais, France.
    Moller, K. T.
    Aarhus Univ, Dept Chem, iNANO, Ctr Mat Crystallog, Langelandsgade 140, DK-8000 Aarhus, Denmark.
    Jensen, T. R.
    Aarhus Univ, Dept Chem, iNANO, Ctr Mat Crystallog, Langelandsgade 140, DK-8000 Aarhus, Denmark.
    Akiba, E.
    205 Kyushu Univ, Int Res Ctr Hydrogen Energy, Nishi Ku, 744 Motooka, Fukuoka, Fukuoka 8190395, Japan.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Hydrogen sorption in TiZrNbHfTa high entropy alloy2019In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 775, p. 667-674Article in journal (Refereed)
    Abstract [en]

    High Entropy Alloys (HEA), where five or more elements are mixed together in near equiatomic ratios offer promising properties as hydrogen storage materials due to their ability to crystallize in simple cubic structures in the presence of large lattice strain originating from the different sizes of the atoms. In this work, the hydrogen absorption and desorption as well as the cycling properties of the TiZrNbHfTa HEA have been studied by in situ Synchrotron X-Ray diffraction, Pressure-Composition-Isotherm, Thermal Desorption Spectroscopy and Differential Scanning Calorimetry. The alloy crystallizes in a cubic bcc phase and undergoes a two-stage hydrogen absorption reaction to a fcc dihydride phase with an intermediate tetragonal monohydride, very similar to the V-H system. The hydrogen absorption/desorption in TiZrNbHfTa is completely reversible and the activation energy of desorption could be calculated. Furthermore, we have observed an interesting macrostructure following parallel planes after the formation of the dihydride phase, which is retained after desorption.

  • 569.
    Zou, Yiming
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Larsson, F.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Larsson, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Effect of CVD diamond growth by doping with nitrogen2013In: Theoretical Chemistry accounts, ISSN 1432-881X, E-ISSN 1432-2234, Vol. 133, no 2, p. 1432-Article in journal (Refereed)
    Abstract [en]

    The purpose with the present investigation has been to support and explain the experimental observation made regarding the enhancing effect by N doping on especially the diamond (100)-2 x 1 growth rate. Within the present study, also the commonly observed diamond (111) and (110) surfaces were included, all assumed to be H-terminated. Density functional theory calculations were used, based on a plane wave approach under periodic boundary conditions. It was shown that the surface H abstraction reaction is most probably the rate-limiting step during diamond growth. In addition, the results showed that it is N, substitutionally positioned within the upper diamond surface, that will cause the growth rate improvement, and not nitrogen chemisorbed onto the growing surface in the form of either NH (or NH2). The here presented numerical value for the growth rate enhancement for the diamond (100)-2 x 1 surface is almost identical with the experimentally obtained one (3.7 vs. 3.6). In addition, the (111) and (110) surfaces were shown to undergo a different growth rate enhancement, with about half as much for the (111) and (110) surfaces as compared to the diamond (100)-2 x 1 surface (1.9, 1.7 vs. 3.7). Despite the rate improvement for all surface planes, this difference will bring about a preferred diamond (100) surface texture.

  • 570.
    Zou, Yiming
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Larsson, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Effect of Boron Doping on the CVD Growth Rate of Diamond2016In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 120, no 19, p. 10658-10666Article in journal (Refereed)
    Abstract [en]

    The purpose with the present study has been to theoretically investigate the effect of boron doping on the diamond growth rate. The most frequently observed diamond surface planes (100), (111) and (110) were thereby carefully investigated using density functional theory calculations under periodic boundary conditions. It was shown that both the thermodynamic and kinetic aspects of the diamond growth process will be severely affected by the B dopant (as compared with the non-doped situations). More specifically, the results showed that B (positioned within the 2nd atomic C layer) will cause an enhancement in the growth rate. On the other hand, the effect of B positioned in the other atomic C layers showed a decreased growth rate. These observations did not only correlate with experimental results but did also explain the anomalous variations in the diamond growth rate (i.e., either increase or decrease) with B doping.

  • 571.
    Zuleta, Marcelo
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Edvinsson, Tomas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Yu, Shun
    Ahmadi, Sareh
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Göthelid, Mats
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Light-induced rearrangements of chemisorbed dyes on anatase(101)2012In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 14, no 30, p. 10780-10788Article in journal (Refereed)
    Abstract [en]

    Photoinduced molecular rearrangements are important in daily events essential for life such as visual perception and photo-protection of light harvesting complexes in plants. In this study we demonstrate that similar photoarrangements appear in an analogous technological application where the device performance is controlled by chromophores in sensitized anatase TiO2, one of the main components for light-harvesting in dye-sensitized solar cells (DSC). STM reveals that illumination leads to distortions of organic dyes containing conjugated backbones and of cis-bis(isothiocyanate)-bis-(2,2'-bipyridyl-4,4'-dicarboxylate)ruthenium(II)-bis(tetrabutylammonium), known as N719. The dyes were adsorbed in a closed-packed mode on an anatase(101) single crystal surface and imaged in the dark and under white light illumination in an ultra-high vacuum (UHV). STM images of N719 clearly suggest rearrangements caused by rotation of the dye. Conversely, organic dyes rearrange by photoisomerization depending on the number of double bonds, their position in the molecular structure and on the ligand modifications.

  • 572.
    Ångström, Jonas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    Johansson, Robert
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Balmes, Olivier
    Sørby, Magnus H.
    Scheicher, Ralph H.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Ulrich, Häusermann
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Hydrogen Absorption in Rare-Earth-Gallide Zintl-Phases LnGa (Ln=Nd, Gd)Manuscript (preprint) (Other academic)
  • 573.
    Ångström, Jonas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Johansson, Robert
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Rude, Line Holdt
    Gundlach, Carsten
    Scheicher, Ralph H.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Jensen, Torben R.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Hydrogen storage properties of the pseudo binary Laves phase (Sc1-xZrx)(Co1-yNiy)2 system2013In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 38, no 23, p. 9772-9778Article in journal (Refereed)
    Abstract [en]

    The (Sc1-xZrx)(Co1-yNiy)(2)-H-z system has been studied using both experimental techniques and ab initio calculations. The material was synthesised through high temperature synthesis and characterised using powder XRD. Hydrogen absorption and desorption was studied in-situ using synchrotron radiation. Maximal storage capacity increased when Co replaced Ni and substitution of Sc for Zr increased the equilibrium pressure. Density functional based calculations reproduce the experimental trends in terms of cell parameters both for the non-hydrogenated systems as well as for the hydrogenated systems, and helped to quantitatively understand the observed hydrogen uptake properties. 

  • 574. Ångström, Jonas
    et al.
    Johansson, Robert
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Sarkar, Tapati
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Sorby, Magnus H.
    Inst Energy Technol, Phys Dept, NO-2027 Kjeller, Norway..
    Zlotea, Claudia
    CNRS UPEC, Inst Chim & Mat Paris Est, F-94320 Thiais, France..
    Andersson, Mikael S.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Nordblad, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Scheicher, Ralph H.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Haussermann, Ulrich
    Stockholm Univ, Dept Mat & Environm Chem, SE-10691 Stockholm, Sweden..
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Hydrogenation-Induced Structure and Property Changes in the Rare-Earth Metal Gallide NdGa: Evolution of a [GaH](2-) Polyanion Containing Peierls-like Ga-H Chains2016In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 55, no 1, p. 345-352Article in journal (Refereed)
    Abstract [en]

    The hydride NdGaH1+x (x approximate to 0.66) and its deuterized analogue were obtained by sintering the Zintl phase NdGa with the CrB structure in a hydrogen atmosphere at pressures of 10-20 bar and temperatures near 300 degrees C. The system NdGa/NdGaH1+x exhibits reversible H storage capability. H uptake and release were investigated by kinetic absorption measurements and thermal desorption mass spectroscopy, which showed a maximum H concentration corresponding to "NdGaH2" (0.93 wt % H) and a two-step desorption process, respectively. The crystal structure of NdGaH1+x was characterized by neutron diffraction (P2(1)/m, a = 4.1103(7), b = 4.1662(7), c = 6.464(1) angstrom, beta = 108.61(1)degrees Z = 2). H incorporates in NdGa by occupying two distinct positions, H1 and H2. HI is coordinated in a tetrahedral fashion by Nd atoms. The H2 position displays flexible occupancy, and H2 atoms attain a trigonal bipyramidal coordination by centering a triangle of Nd atoms and bridging two Ga atoms. The phase stability and electronic structure of NdGaH1+x, were analyzed by first-principles DFT calculations. NdGaH1H2 (NdGaH2) may be expressed as Nd3+(H1(-)[GaH2](2-). The two-dimensional polyanion [GaH](2-) features linear -H-Ga-H-Ga- chains with alternating short (1.8 A) and long (2.4 angstrom) Ga-H distances, which resembles a Peierls distortion. H2 deficiency (x < 1) results in the fragmentation of chains. For x = 0.66 arrangements with five-atom moieties, Ga-H-Ga-H-Ga are energetically most favorable. From magnetic measurements, the Curie-Weiss constant and effective magnetic moment of NdGaH1.66 were obtained. The former indicates antiferromagnetic interactions, and the latter attains a value of similar to 3.6 mu(B), which is typical for compounds containing Nd3 ions.

  • 575.
    Ångström, Jonas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Berger, Rolf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Real-time in-situ monitoring of the topotactic transformation of TlCu3Se2 into TlCu2Se22015In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 15, p. 321-325Article in journal (Refereed)
    Abstract [en]

    The solid state transformation of monoclinic TlCu3Se2 into tetragonal TlCu2Se2 by oxidative copper leaching in concentrated ammonia solution has been studied in situ by the use of synchrotron radiation. The diffraction patterns of parent and daughter phase are both sharp, indicating a strong topotactic relationship between them that effectuates a rapid change by “chimie douce” performed at +19 °C.

    The transformation rate is strongly connected to the access of oxygen from the surrounding air. The transformation was followed in a real-time mode, being almost complete after 2.5 h with 1 h incubation due to low oxygen content, as shown from refining the diffraction patterns by Rietveld profile technique.

  • 576.
    Ångström, Jonas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Zlotea, Claudia
    Latroche, Michel
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Hydrogen-sorption properties of Nb4M0.9Si1.1 (M = Co,Ni) hydrides2015In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 40, no 6, p. 2692-2697Article in journal (Refereed)
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