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  • 1.
    Barzegar, Hamid Reza
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics. Department of Physics, University of California, Berkeley, USA.
    Pham, Thang
    Talyzin, Alexandr V.
    Zettl, Alex
    Synthesis of graphene nanoribbons inside boron nitride nanotubes2016In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 253, no 12, p. 2377-2379Article in journal (Refereed)
    Abstract [en]

    We report on bottom-up synthesis of graphene nanoribbons inside boron nitride nanotubes, using coronene molecules as building blocks. The synthesized ribbons are one or two coronene molecules wide, depending on the diameter of the host nanotube. The encapsulated carbon nanostructures can be eliminated from the inner cavity of the filled boron nitride nanotube via oxidation without any damage to the nanotube structure.

  • 2. Dunn, Gabriel
    et al.
    Shen, Konlin
    Barzegar, Hamid Reza
    Umeå University, Faculty of Science and Technology, Department of Physics. Department of Physics, University of California, Berkeley, California 94720, United States ‡ Department of Physics, Umeå University, SE-901 87 Umeå, Sweden § Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States ∥ Kavli Energy NanoSciences Institute at the University of California, Berkeley and the Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
    Shi, Wu
    Belling, Jason
    Nguyen, Tran NH
    Barkovich, Emil
    Chism, Kyle
    Maharbiz, Michel M
    DeWeese, Michael R
    Zettl, Alex
    Selective Insulation of Carbon nanotubes2017In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 254Article in journal (Refereed)
    Abstract [en]

    We demonstrate a method for the selective encapsulation of carbonnanotubes in thin parylene films using iron as a sacrificial lift-off layer. Theiron serves as an inhibitor of parylene deposition and prevents the parylenemolecules from linking, thus facilitating selective area coating after lift-off.

  • 3. Halonen, Niina
    et al.
    Sapi, Andras
    Nagy, Laszlo
    Puskas, Robert
    Leino, Anne-Riikka
    Maklin, Jani
    Kukkola, Jarmo
    Toth, Geza
    Wu, Ming-Chung
    Liao, Hsueh-Chung
    Su, Wei-Fang
    Shchukarev, Andrey
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Mikkola, Jyri-Pekka
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Kukovecz, Akos
    Konya, Zoltan
    Kordas, Krisztian
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Low-temperature growth of multi-walled carbon nanotubes by thermal CVD2011In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 248, no 11, p. 2500-2503Article in journal (Refereed)
    Abstract [en]

    Low-temperature thermal chemical vapor deposition (thermal CVD) synthesis of multi-walled carbon nanotubes (MWCNTs) was studied using a large variety of different precursor compounds. Cyclopentene oxide, tetrahydrofuran, methanol, and xylene: methanol mixture as oxygen containing heteroatomic precursors, while xylene and acetylene as conventional hydrocarbon feedstocks were applied in the experiments. The catalytic activity of Co, Fe, Ni, and their bi-as well as tri-metallic combinations were tested for the reactions. Low-temperature CNT growth occurred at 400 degrees C when using bi-metallic Co-Fe and tri-metallic Ni-Co-Fe catalyst (on alumina) and methanol or acetylene as precursors. In the case of monometallic catalyst nanoparticles, only Co (both on alumina and on silica) was found to be active in the low temperature growth (below 500 degrees C) from oxygenates such as cyclopentene oxide and methanol. The structure and composition of the achieved MWCNTs products were studied by scanning and transmission electron microscopy (SEM and TEM) as well as by Raman and X-ray photoelectron spectroscopy (XPS) and by X-ray diffraction (XRD). The successful MWCNT growth below 500 degrees C is promising from the point of view of integrating MWCNT materials into existing IC fabrication technologies. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

  • 4.
    Kastberg, Anders
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Dion, Claude
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Hagman, Henning
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Zelan, Martin
    Umeå University, Faculty of Science and Technology, Department of Physics.
    A three-dimensional Brownian motor, realised with symmetric optical lattices2009In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 246, no 5, p. 999-1005Article in journal (Refereed)
    Abstract [en]

    A three-dimensional Brownian motor is realised using lasercooled caesium atoms trapped in a system of two static, and individually symmetric, optical lattices; a so-called double optical lattice. Isotropic fluctuations, emanating from light scattering, are rectified, and the diffusion of the ensemble of atoms is biased, with a resulting constant velocity that is controllable both in direction and magnitude. The working principle of the Brownian motor can be seen as a pulsation between two different potentials, both symmetric but around different points. The correlation between interferometric spatial offsets, and imbalance in optical pumping rates, leads to a spatio-temporal asymmetry sufficient for generating a controlled, directed motion.

  • 5.
    Makarova, T. L.
    Umeå University.
    Graphite under the magnetic force microscope2007In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 244, no 11, p. 4138-4142Article in journal (Refereed)
  • 6.
    Makarova, Tatiana L.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Zakharova, I. B.
    State Polytechnical University, St Petersburg, Russia.
    Kvyatkovskii, O. E.
    Ioffe Physico-Technical Institute, St Petersburg, Russia.
    Buga, S. G.
    Technological Institute for Superhard and Novel Carbon Materials, Troitsk, Russia.
    Volkov, A. P.
    Technological Institute for Superhard and Novel Carbon Materials, Troitsk, Russia.
    Shelankov, Andrei L.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Experimental realization of high spin states in dilutely hydrogenated fullerenes2009In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 246, no 11-12, p. 2778-2781Article in journal (Refereed)
    Abstract [en]

    A novel method for preparing dilutely hydrogenated fullerenes H:C60 is presented. DFT calculations of the Raman spectra at the B3LYP/3-21G level are compared with the experimental data. Under the laser treatment these phases form a rich variety of dimeric and polymeric structures, quite in contrast to pristine C60 which forms dimers and polymers bonded through the [2 + 2] addition, and in contrast to heavily hydrogenated fullerenes which do not polymerize at all. Dilutely hydrogenated fullerenes polymerize differently, forming both double bonded structures and single bonded dimers. We have shown that dilute hydrogenation of C60 creates large amount of unpaired spins which disappear due to the formation of diamagnetic single bonded dimers.

  • 7.
    Makarova, Tatiana
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Ricco, Mauro
    Pontiroli, Daniele
    Mazzani, Marcello
    Belli, Matteo
    Goffredi, Angelo
    Ageing effects in nanographite monitored by Raman spectroscopy2008In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 245, no 10, p. 2082-2085Article in journal (Refereed)
    Abstract [en]

    The structural relaxation of nanographite ball-milled in argon atmosphere and stored in evacuated ampoules, has been studied by monitoring the evolution of the Raman spectra. Reduction of some Raman bands associated with “in-plane” structural defects, such as vacancies, dislocations or grain boundaries, and those associated with “out-of-plane” defects, such as stacking faults, is accompanied by the rise of new bands around 1180 and 2000 cm–1. The development of these bands is suppressed in nanographite samples exposed to a flux of pure anhydrous hydrogen.

  • 8.
    Makarova, Tatiana
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Shelankov, Andlei L.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Serenkov, Igor T.
    Sakharov, Vladimir I.
    Magnetism in graphite induced by irradiation of hydrogen and helium atoms: a comparative study2010In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 247, no 11-12, p. 2988-2991Article in journal (Refereed)
    Abstract [en]

    To identify the origin of defect-induced magnetism in ion-irradiated graphite, a comparative study of samples of graphite irradiated with hydrogen H+ and helium He+ ions is performed. Directionally dependent magnetic properties, atomic/magnetic force microscopy studies suggest that the induced magnetic moments are located along the vertically aligned grain boundaries. Compared to the case of the hydrogen ion irradiation, the optimal helium irradiation dose is an order of magnitude lower. From this we conclude that the hydrogen chemistry is essentially irrelevant, and the ferromagnetic-like response of the irradiated graphite is due to structural defects regardless of their origin.

  • 9.
    Makarova, Tatiana
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Zagaynova, Valeria
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Spitsyna, Natalia G.
    Fullerene-induced magnetization training effect in single molecular magnet2010In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 247, no 11, p. 3018-3021Article in journal (Refereed)
  • 10. Mäklin, Jani
    et al.
    Halonen, Niina
    Toth, Géza
    Sápi, András
    Kukovecz, Ákos
    Kónya, Zoltán
    Jantunen, Heli
    Mikkola, Jyri-Pekka
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Kordas, Krisztián
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Thermal diffusivity of aligned multi-walled carbon nanotubes measured by the flash method2011In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 248, no 11, p. 2508-2511Article in journal (Refereed)
    Abstract [en]

    Thermal diffusivity of freestanding catalytic chemical vapor deposition (CCVD) grown multi-walled carbon nanotube (MWCNT) forests (height of 1.5 and 1.9 mm) was characterized in the temperature range between 25 and 200 degrees C. Copper and Al-alloy metal blocks were used as references for validation of the experimental setup. The measurements were carried out along the MWCNT alignment direction with a thermal property analyzer that uses the flash method. The thermal diffusivities measured at room temperature for as-grown and post-annealed (2 h at 480 degrees C in open air) samples were found to be similar to 0.45 and similar to 0.23 cm(2)/s, respectively. In both cases, the thermal diffusivity values were slightly decreasing with increasing temperature. The observed decrease in diffusivity after annealing is most probably due to the loss of amorphous carbon in the specimens and also because of the increased defect density in the nanotube walls resulting in a more pronounced phonon scattering in the lattice. The measured thermal diffusivities for as-grown samples agree with data reported elsewhere for similar MWCNT materials [W. Yi et al., Rev. B 59, 9015 (1999) and T. Borca-Tasciuc et al., J. Appl. Phys. 98, 054309 (2005)]. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

  • 11.
    Nitze, Florian
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Andersson, Britt
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Wågberg, Thomas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Ammonia assisted growth of multiwalled carbon nanotubes2009In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 246, no 11-12, p. 2440-2443Article in journal (Refereed)
    Abstract [en]

    Bamboo structured nitrogen-containing carbon nanotubes are grown on e-beam deposited thin metal films (cobalt/iron) by chemical vapor deposition. The approach uses ammonia as supporting gas to form nano catalyst particles in the pretreatment phase. Ammonia is also used as nitrogen source. The effect of ammonia on the grown structures at different temperatures (720 and 810 °C) is investigated by SEM, TEM and Raman spectroscopy. We show that ammonia promotes growth of vertically aligned CNT carpets on thicker metal films (5 nm) than usually used. At the same time ammonia is inducing a high amount of defects but this effect changes significantly with temperature. At 720 °C defects are clearly ammonia induced while at 810 °C the defects seem to be induced by a different mechanism. Furthermore, the presence of ammonia in both pretreatment phase and growth phase reduces the outer diameter of the grown nanotubes.

  • 12.
    Nitze, Florian
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Barzegar, Hamid Reza
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Wagberg, Thomas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Easy synthesis of Pd fullerene polymer structures from the molten state of tris(dibenzylideneacetone)dipalladium(0)2012In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 249, no 12, p. 2588-2591Article in journal (Refereed)
    Abstract [en]

    Pd fullerene composites were first synthesized and studied in the early 90s by for example Nagashima et al. In this study we present a novel and rapid approach to synthesize Pd fullerides based on direct reaction of C60 with Pd2dba3. We show that the Pd fullerene polymer phase forms at temperatures around the melting point of Pd2dba3 (150 degrees C) and that it proceeds upon further annealing while releasing dba. The synthesis reactions were studied in TGA/DSC. TEM revealed that the material easily collapses under the electron beam into nanoparticles. Under very low doses almost no particles can be found. Similarly, Raman spectroscopy confirmed the formation of Pd fulleride polymers but also supported the collapse of the Pd fulleride phase when irradiated by high laser power. CVD experiments have been conducted on directly coated Si substrates showing similar results to previous reports, namely that Pd2C60 is an efficient catalysts for the growth of helical carbon nanofibers. Our study gives both insights into the formation of nanoparticles as well as the synthesis of C60 polymers. The method is also compatible with direct coating processes making it useful for a broad spectrum of CVD and catalysis applications. (C) 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

  • 13.
    Talyzin, Alexandr V.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Anoshkin, Ilya V.
    Nasibulin, Albert G.
    High-temperature transformations of coronene-based graphene nanoribbons encapsulated in SWNTs2015In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 252, no 11, p. 2491-2495Article in journal (Refereed)
    Abstract [en]

    Coronene-based graphene nanoribbons encapsulated inside single-walled carbon nanotubes (SWNTs) were prepared 440 degrees C under Ar and annealed at temperatures up to 825 degrees C. The structural modifications of coronene/SWNT samples were studied using Raman spectroscopy and transmission electron microscopy. Coronene and coronene-based graphene nanoribbons are hydrogen terminated and annealing at temperatures above the stability limit of C-H bonds were expected to result in formation of new products. Indeed, Raman spectroscopy revealed the appearance of new sharp peaks after annealing of samples above 650 degrees C. The possible nature of encapsulated products produced by annealing of hydrogen terminated nanoribbons inside SWNTs is discussed. 

  • 14.
    You, Shujie
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Yu, Junchun
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Talyzin, Alexandr
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Solvation of graphite oxide in water-methanol binary polar solvents2012In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 249, no 12, p. 2568-2571Article in journal (Refereed)
    Abstract [en]

    The phase transition between two solvated phases was studied by DSC for graphite oxide (GO) powders immersed in water–methanol mixtures of various compositions. GO forms solid solvates with two different compositions when immersed in methanol. Reversible phase transition between two solvate states due to insertion/desertion of methanol monolayer occurs upon temperature variations. The temperature point and the enthalpy (DH) of the phase transition are maximal for pure methanol and decrease linearly with increase of water fraction up to 30%.

     

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