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  • 101. Jarlborg, Thomas
    et al.
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Physics.
    Andersson, Göran
    Umeå University, Faculty of Science and Technology, Physics.
    Rapp, Östen
    Electron-Phonon Interaction of fcc and dhcp La under Pressure1987In: Japanese Journal of Applied Physics, volume 26, Supplement 26-3-2: Proceedings of the 18th International Conference on Low Temperature Physics (LT-18), Kyoto 1987, Part 2, The Japan Society of Applied Physics , 1987, p. 919-920Conference paper (Refereed)
    Abstract [en]

    The pressure dependence of the electron-phonon interaction of La has been studied for both phases by two methods: One is a calculation of λ and the other uses the calculated plasma frequency and the measured temperature and pressure dependence of the electrical resistivity. These results as well as a calculation of the spin-fluctuation contribution suggest that quenching of spin-fluctuations with pressure contribute to the increase of Tc with pressure in La.

  • 102. Johari, G. P.
    et al.
    Andersson, Ove
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Instability and thermal conductivity of pressure-densified and elastically altered orientational glass of Buckminsterfullerene2018In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 148, no 14, article id 144502Article in journal (Refereed)
    Abstract [en]

    We report on the temperature, pressure and time (T, p and t)- dependent features of thermal conductivity, k, of partially ordered, non-equilibrium state of C60-OG, the orientational glass of Buckminsterfullerene (at T below the orientational freezing temperature Tog) made more unstable (i) by partially depressurizing its high-p formed state to elastically expand it, and (ii) by further pressurizing that state to elastically contract it. The sub-Tog effects observed on heating of C60-OG differ from those of glasses, because phonon propagation depends on the ratio of two well-defined orientational states of C60 molecules and the density of the solid. A broad peak-like feature appears at T near Tog in the k-T plots of C60-OG formed at 0.7 and heated at 0.2 GPa, which we attribute to partial overlap of the sub-Tog and Tog features. A sub-Tog local minimum appears in the k -T plots at T well below Tog  of C60-OG formed at 0.1 GPa and heated at 0.5 GPa, and corresponds to the state of maximum disorder. Although Buckminsterfullerene is regarded as an orientationally-disordered crystal, variation of its properties with T and p is qualitatively different from other such crystals. We discuss the findings in terms of the nature of its disorder, sensitivity of its rotational dynamics to temperature and the absence of the Johari-Goldstein relaxation. All seem to affect the phenomenology of its glass-like transition.

  • 103. Launois, Pascale
    et al.
    Moret, Roger
    Persson, Per-Axel
    Umeå University, Faculty of Science and Technology, Physics.
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Physics.
    Pressure polymerized C60 single crystals: First x-ray diffraction results1998In: Molecular Nanostructures: Proceedings of the International Winterschool on Electronic Properties of Novel Materials, Kirchberg 1997, Singapore: World Scientific , 1998, p. 348-352Conference paper (Refereed)
    Abstract [en]

    C60 single crystals compressed at approx. 1 GPa and heated at about 300 C are found to polymerize in one dimension without losing their crystalline order. The resulting structure is orthrhombic, with space group Pmnn and parameters a=9.14 Å, b=9.9 Å and c=14.66 Å. The X-ray single crystal results allow us to derive a polymerization mechanism, which may also, for instance, apply to one dimensional C60 polymers in the doped compounds. The new polymer phase is discussed with respect to the C60 pressure-temperature diagram. The comparison with the A1C60 polymers raises questions about the interchain and the alkali metal - fullerene interactins.

  • 104. Lelaurain, Michelle
    et al.
    Marêché, Jean-Francois
    McRae, Edward
    Andersson, Odd E.
    Umeå University, Faculty of Science and Technology, Physics.
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Physics.
    A study of temperature and pressure induced structural and electronic changes in SbCl5 intercalated graphite: Part I: Structural aspects1992In: Journal of Materials Research, ISSN 0884-2914, E-ISSN 2044-5326, Vol. 7, no 11, p. 2978-2988Article in journal (Refereed)
    Abstract [en]

    We have studied the effects of temperature (10 = T = 295 K) and pressure (0 = p = 0.8 GPa) on the state of intercalate layer crystallization in SbCl5 graphite intercalation compounds of stages 2, 4, and 8. At room temperature (RT), the intercalate layer may in some second stage compounds be fully crystallized and lowering the temperature creates no further modifications. In all other cases, i.e., those in which the intercalate layer has only partial crystallization at RT, lowering T leads to the formation of new in-plane unit cells, the final state depending on the kinetics. Applying pressure to above 0.3–0.5 GPa results in crystallization in all cases, different from that induced simply by lowering of the temperature. We discuss the unit cells observed and the relationships they bear to each other in the light of other works on similar compounds.

  • 105.
    Liu, Bingbing
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Carlsten, Jan
    Umeå University, Faculty of Science and Technology, Physics.
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Physics.
    Bromine doped single-walled carbon nanotubes2001In: Nanotubes and Related Materials: Proceedings of the MRS Fall Meeting 2000, Boston, Warrendale: Materials Research Society , 2001, p. A13.36-Conference paper (Refereed)
    Abstract [en]

    Raman spectra for three SWNT samples doped with Br2 were studied using different excitation energies, 2.41 eV and 1.58 eV. One sample was also studied under high pressure up to 2GPa. The vibrations in the low frequency range behave similarly for all samples. With an excitation energy of 1.58eV, additional peaks at ca 240 cm-1 and 209 cm-1 are observed. With increasing pressure, the peak at 209 cm-1 gradually softens by 2~3 cm-1 and becomes very weak at 1.7 GPa, while a new broader peak at ca 250 cm-1 remains constant up to 2 GPa. A number of high intensity overtone modes are observed under high pressure. These results indicate that the vibrations are attributed to bromine, not to the breathing modes of SWNTs, and that bromine resides in the bundles, possibly also inside tubes as a form of polymer.

  • 106. Liu, Bingbing
    et al.
    Cui, Qiliang
    Yu, Miao
    Zou, Guangtian
    Carlsten, Jan
    Umeå University, Faculty of Science and Technology, Physics.
    Wågberg, Thomas
    Umeå University, Faculty of Science and Technology, Physics.
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Physics.
    Raman study of bromine-doped single-walled carbon nanotubes under high pressure2002In: Journal of Physics: Condensed Matter vol. 14 issue no. 44: Proceedings of the Joint 18th Conference on High Pressure Science and Technology (AIRAPT 18) and the 11th High Pressure Conference of China (HPCC-11), Beijing 2001, Bristol: Institute of Physics , 2002, p. 11255-11259Conference paper (Refereed)
    Abstract [en]

    Raman results for different single-walled carbon nanotube bundles doped withBr2 were studied both at ambient pressure and under high pressure up to 6 GPa.Our study indicates that bromine resides in the interstitial channel of nanotubebundles as a form of polymer.

  • 107. Liu, Bingbing
    et al.
    Hou, Yuanyuan
    Wang, Lin
    Liu, Dedi
    Yu, Shidan
    Zou, Bo
    Cui, Tian
    Zou, Guangtian
    Iwasiewicz-Wabnig, Agnieszka
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Department of Physics.
    High pressure and high temperature induced polymeric C60 nanocrystal2008In: Diamond and related materials, vol. 17, issue 4-5: Proceedings of the International Conference on New Diamond and Nano Carbons 2007 (NDNC2007), Amsterdam: Elsevier B.V. , 2008, p. 620-623Conference paper (Refereed)
    Abstract [en]

    In this paper, C60 nanosheets with polymeric phases have been obtained under various high pressures and high temperatures, including orthorhombic and tetragonal polymeric phases. The structures have been identified and compared with those of nanorods by photoluminescence and Raman spectroscopies. The main fluorescence band shifted from 1.70 eV in the monomeric phase to near infrared in the polymeric phase when pressure and temperature were increased. The difference of photoluminescence and Raman spectra between nanosheets and nanorods samples treated under the same conditions is probably caused by different polymerization degree in these samples because of different shapes.

  • 108. Liu, Bingbing
    et al.
    Hou, Yuanyuan
    Wang, Lin
    Zou, Guangtian
    Iwasiewicz, Agnieszka
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Department of Physics.
    High pressure and high temperature induced polymeric C60 nanorods and their photoluminiscence properties.2007In: Materials Research at High Pressure: Proceedings of Symposium PP at the 2006 MRS Fall Meeting, Boston, MA, USA; Materials Research Society Symposium Proceedings vol. 987E, Warrendale: Maerials Research Society , 2007, p. 99-103Conference paper (Refereed)
    Abstract [en]

    We report that C60 nanorods of three polymeric phases have been synthesized under high pressure and high temperature and that the photoluminescence properties of these polymeric nanorods also have been studied. C60 nanorods were fabricated by a facile solution evaporation method. Raman spectra indicate that this material transformed into orthorhombic, tetragonal and rhombohedral polymeric phases under various high pressure and high temperature conditions. SEM measurements show that the shape of the nanorods can be kept under quasi-hydrostatic pressure condition. The photoluminescence intensity of the polymeric C60 nanorods has been enhanced compared with that of the pristine C60 nanorods. The main fluorescence band shifted from 1.70 eV in the monomeric phase to near infrared in the polymeric phase when pressure and temperature were increased. The enhanced fluorescence with adjustable frequency for different polymeric C60 nanorods makes possible potential application in luminescent nanomaterials.

  • 109.
    Liu, Bingbing
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Physics.
    Andersson, Ove
    Umeå University, Faculty of Science and Technology, Physics.
    Olsson, Eva
    Wågberg, Thomas
    Umeå University, Faculty of Science and Technology, Physics.
    Nyeanchi, Emmanuel B.
    Umeå University, Faculty of Science and Technology, Physics.
    Zhu, Xiaomei
    Umeå University, Faculty of Science and Technology, Physics.
    Zou, Guangtian
    Electric resistance of single-walled carbon nanotubes under hydrostatic pressure2001In: Solid State Communications, ISSN 0038-1098, E-ISSN 1879-2766, Vol. 118, no 1, p. 31-36Article in journal (Refereed)
    Abstract [en]

    The electric resistance of single-walled nanotube mats has been studied systematically under both ambient and high hydrostatic pressures up to 1.5 GPa. Both the temperature dependence of the resistance and the magnetoresistance indicate that electrical transport occurs by variable range hopping, apparently in 2D. We suggest that this unexpected dimensionality arises from a fractal network of tubes and bundles. Under hydrostatic pressure (HP) the resistance still shows 2D variable range hopping and decreases with increasing HP. An irreversible increase in localization length and DOS is induced below 0.5 GPa. The behavior is reversible and due to strong interaction of tubes from 0.5 GPa up to 1.05 GPa. These results indicate that 2D variable range hopping occurs within bundles.

  • 110.
    Liu, Bingbing
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Physics.
    Andersson, Ove
    Umeå University, Faculty of Science and Technology, Physics.
    Wågberg, Thomas
    Umeå University, Faculty of Science and Technology, Physics.
    Zou, Guangtian
    Transport properties of single-walled nanotube mats under hydrostatic pressure2000In: Electronic Properties of Novel Materials: Science and Technology of Molecular nanostructures: Proceedings of the XIV Winter School on Electronic Properties of Novel Materials, Kirchberg 2000, Melville: American Institute of Physics (AIP) , 2000, p. 344-348Conference paper (Refereed)
    Abstract [en]

    The study of electrical transport properties of bulk single-walled carbon nanotube (SWNT) materials attracts a lot of attention. However, the transport results differ from sample to sample[l]. Some results show semiconducting behavior with different laws and whether the behavior is dominated by on-tube or on-bundle effects or by interbundle contacts is still unknown. Therefore, further investigation is still meaningful. The effect of hydrostatic pressure(HP), which is expected to significantly change the interaction between tubes or bundles, gives us a further possibility to understand the characteristic properties. Under HP, Raman spectra and electric resistance show pronounced changes at 1.5GPa[2]. In this study, we systematically studied the electric resistance up to 1.5 GPa, giving a different image of the transport behavior.

  • 111. Liu, Bingbing
    et al.
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Physics.
    Li, Dongmei
    Zou, Guangtian
    Resistivity and fractal structure in carbon nanotube networks2002In: Journal of Physics Condensed Matter vol. 14 issue 44: Proceedings of the Joint 18th International Conference on High Pressure Science and Technology (AIRAPT 18) and the 11th High Pressure Conference of China (HPCC-11), Beijing 2001, Bristol: Institute of Physics , 2002, p. 11125-11129Conference paper (Refereed)
    Abstract [en]

    We have measured the temperature and magnetic field dependence of the resistance for bulk samples of single-walled nanotubes treated in different ways. Hydrostatic pressure-treated samples and as-grown samples show a two-dimensional variable-range hopping behaviour while samples treated in non-hydrostatic pressure or in acid for a long time show a three-dimensional transport behaviour. We suggest that the observed two-dimensional behaviour arises from a network structure with a fractal dimension lower than three.

  • 112. Liu, Bingbing
    et al.
    Wang, Lin
    Hou, Yuanyuan
    Yao, Mingguang
    Zou, Guangtian
    Iwasiewicz, Agnieszka
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Department of Physics.
    High-pressure induced polymerization of C60 nanorods2005In: Proceedings of the Joint 20th AIRAPT and 43rd EHPRG Conf. on High Pressure Science and Technology, Karlsruhe 2005, 2005, p. Nanomat-O133Conference paper (Other academic)
    Abstract [en]

    C60 nanorods, about 200 nm in diameter and several micrometers in length and with a rectangular cross section, have been synthesized by a simple solution-growth method. Raman spectroscopy and TEM indicate that the C60 nanorods have a fcc crystalline structure similar to that of pristine C60. Nanorods were polymerized at high temperature and high pressure below 2 GPa. Two different polymeric structures, orthorhombic and tetragonal as determined by Raman spectroscopy, have been obtained under different high temperature and high pressure conditions. The high-pressure induced polymeric samples keep the original nanometer scale rod shape.

  • 113. Liu, Bingbing
    et al.
    Wang, Lin
    Hou, Yuanyuan
    Yao, Mingguang
    Zou, Guangtian
    Iwasiewicz, Agnieszka
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Synthesis and high pressure induced polymerization of C60 nanorod2004In: Proceedings of 2nd Asian Conference on High Pressure Research ACHPR-2, 1-5 November 2004, Nara, Japan, 2004, p. achpr-0446.pdfConference paper (Other academic)
  • 114. Liu, Bingbing
    et al.
    Wang, Lin
    Zou, Guangtian
    Iwasiewicz, Agnieszka
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Department of Physics.
    A facile solution method to synthesis of C60 nanorods2006In: Materials Research Society Symposium Proceedings vol. 963: Nanowires and Carbon Nanotubes - Science and Applications; Proceedings of Symposium Q of the 2006 MRS Fall Meeting / [ed] P. Bandaru, M. Endo, I.A. Kinloch and A.M. Rao, Warrendale: Materials Research Society , 2006, p. 49-54Conference paper (Refereed)
    Abstract [en]

    We report here a facile solution method to synthesis of C60 nanorods. A very simple and effective solvent, neat m-xylene, from which C60 can rapidly grow into individual novel nanorods with widths and thicknesses of the order of nanometers was found as a shape controller. These unusual nanorods can easily grow on various substrates such as glass and silicon, and nanorods with different diameters and length-to-diameter ratios can be synthesized under different growth conditions. The smallest nanorods we obtained have widths smaller than 30 nm. The nanorods obtained are highly crystalline and single phase.

  • 115.
    Liu, Bingbing
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Wågberg, Thomas
    Umeå University, Faculty of Science and Technology, Physics.
    Nyeanchi, Emmanuel B.
    Umeå University, Faculty of Science and Technology, Physics.
    Makarova, Tatiana L.
    Umeå University, Faculty of Science and Technology, Physics.
    Zhu, Xiaomei
    Umeå University, Faculty of Science and Technology, Physics.
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Physics.
    Yang, R.
    Li, D.
    Gao, C.
    Yang, H.
    Zou, Guangtian
    Li, H.-D.
    Olsson, Eva
    Synthesis and characterization of single-walled nanotubes produced with Ce as catalyst2000In: Molecular Materials: Molecular Crystals and Liquid Crystals Section C, vol. 13: Proceedings of the 4th International Workshop on Fullerenes and Atomic Clusters (IWFAC'99), St. Petersburg 1999, Overseas Publishers Association N.V. , 2000, p. 75-80Conference paper (Refereed)
    Abstract [en]

    We have studied the effect of using rare-earth elements C (typically +4 oxide state) and Eu (typically +2 oxide state) together with nanometer Ni as catalysts to synthesize SWNT in high yield by arc evaporation. A black collar deposit containing mainly SWNT was formed in the presence of Ce/Ni while only nanometer carbon particles were formed using Eu/Ni, as identified by SEM, TEM and Raman spectra. The Raman spectra of our SWNT mats show difference from spectra shown in the literature in a low frequency range, indicating that our mats contain chiral tubes. The temperature dependent resistance of SWNT mats was also measured. A semiconducting behaviour was observed with a negative dR/dT and no resistance minimum from 2 to 350 K. The resistance follows a 2D variable range hopping behaviour.

  • 116.
    Liu, Bingbing
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Wågberg, Thomas
    Umeå University, Faculty of Science and Technology, Physics.
    Olsson, Eva
    Yang, Ruseng
    Li, Hongdong
    Zhang, Shulin
    Yang, Haibin
    Zou, Guangtian
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Physics.
    Synthesis and characterization of single-walled nanotubes produced with Ce/Ni as catalysts.2000In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 320, no 3-4, p. 365-372Article in journal (Refereed)
    Abstract [en]

    SWNTs were synthesized in high yield in the presence of Ce/Ni as catalyst. Raman and SEM results show that a fraction of the tubes are chiral and have small diameters (the smallest one is 0.79 nm), indicating that Ce plays an important role in the formation. Acid treatment is effective in eliminating impurities but changes the morphology and the electric resistance of mats with increasing treatment time. The resistance of as-grown and short time acid-treated mats follow a 2D VRH behaviour while mats treated for a long time follow a 3D model. The results indicate that hopping conduction occurs on bundles or on tubes and that there are intrinsic links between tubes in as-grown mats.

  • 117. Liu, Bingbing
    et al.
    Yu, Miao
    Li, Dong-Mei
    Cui, Tian
    Wang, Lin
    Yao, Mingguang
    Yu, Shi-Dan
    Zou, Guang-Tian
    Wang, Xu
    Zhao, Bing
    Sundqvist, Bertil
    Umeå University.
    Effects of silver films with different nano-particle sizes on SERS of single-walled carbon nanotubes2005In: Chemical Journal of the Chinese Universities, ISSN 0251-0790, Vol. 26, no 10, p. 1930-1933Article in journal (Refereed)
    Abstract [en]

    Surface-enhanced Raman scattering (SERS) spectra of single-walled carbon nanotubes (SWCNTs) on silver films with different nano-particle sizes from 20 to 100 nm deposited on quartz and glass substrates were studied systematically. The characteristic Raman spectral features of SWCNT G-band and D-band were analyzed. The two bands show a similar tendency with the change of nano-particle size of silver on quartz and glass substrates. The position and the intensity of the G-band are less sensitive to the films' silver particle sizes in the studied range, indicating that hexagonal carbon rings are stable and have a weak interaction with silver films. The shape of the D-band depends on the silver size. The smaller the silver particle size, the more the contribution of high frequency vibrations to the D-band, indicating that disorder carbon has a strong interaction with the active silver films.

  • 118. Liu, Dedi
    et al.
    Cui, Wen
    Yao, Mingguang
    Li, Quanjun
    Cui, Tian
    Liu, Bingbing
    Liu, Dongping
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Effects of alcohols on shape-tuning and luminescence-enhancing of C70 nanocrystals2013In: Optical materials (Amsterdam), ISSN 0925-3467, E-ISSN 1873-1252, Vol. 36, no 2, p. 449-454Article in journal (Refereed)
    Abstract [en]

    C70 nanotubes, nanorods and nanoparticles were produced by introducing a series of alcohols as precipitant into a C70/m-xylene solution. The effects of alcohols with different carbon chain lengths on the shape control of C70 nanocrystals were investigated. Alcohols with more than two carbon atoms in the longest chain linked to the hydroxyl groups induced the formation of C70 nanotube/rods. In contrast, alcohols containing two or fewer carbon atoms resulted in C70 nanoparticles. Structural analysis indicated that alcohol molecules exist in the C70 nanocrystals, forming solvated structures. The freshly formed C70 nanotubes and nanoparticles have orthorhombic and hexagonal solvated structures, respectively. Room temperature photoluminescence was further carried out on the solvated C70 nanocrystals to investigate their optical properties. We found that the luminescence intensities of C70 nanocrystals were significantly enhanced by the introduction of alcohols.

  • 119. Liu, Dedi
    et al.
    Liu, Bingbing
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Department of Physics. State Key Laboratory of Superhard Materials, Jilin University, Changchun 130012, PR China.
    Dong, Dapeng
    Li, Zhenghua
    Liu, Dongping
    Photoluminescence changes of C70 nano/submicro-crystals induced by high pressure and high temperature2016In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 6, article id 38470Article in journal (Refereed)
    Abstract [en]

    Hollow C70 nano/submicrocrystals with a fcc lattice structure were treated under various high pressure and high temperature conditions. The energy band structure was visibly changed by the high pressure and high temperature treatment, and the luminescence of the polymerized C70 nano/submicrocrystals was tuned from the visible to the near infrared range. In-situ high pressure experiments at room temperature indicate that pressure plays a key role in the tuning of band gap and PL properties in C70 nanotubes, and temperature plays an important role in the formation of stable intermolecular bonds and thus to define the final red-shift of the PL peaks. The polymeric phases of C70 nanocrystals treated at high pressure and high temperature were identified from Raman spectra, which changed from monomers to a dimer-rich phase and finally to a phase containing larger, disordered C70 oligomers.

  • 120. Liu, Dedi
    et al.
    Wang, Lin
    Cui, Wen
    Yao, Mingguang
    Li, Quanjun
    Li, Zepeng
    Zou, Bo
    Cui, Tian
    Liu, Bingbing
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Synthesis and solid-state studies of self-assembled C60 microtubes2011In: Diamond and Related Materials, vol. 20 issue 2: Proceedings of the international conference on new diamond and nano carbon 2010 (NDNC-2010), 2011, Vol. 20, issue 2, p. 178-182Conference paper (Refereed)
    Abstract [en]

    C60 microtubes were fabricated by a modified solution evaporation method, evaporating a solution of C60 in toluene in an atmosphere of m-xylene at room temperature. The C60 microtubes have outer diameters ranging from 2 to 8 μm. IR spectra, TG analysis and X-ray diffraction showed a solvated structure for the as-grown C60 microtubes. Through a gentle heat-treatment in vacuum, pure C60 microtubes with single crystalline fcc structure were obtained after the elimination of solvents. It is suggested that the C60 microtubes form through self-assembly from several individual C60 nanorods.

  • 121. Liu, Dedi
    et al.
    Yao, Mingguang
    Li, Quanjun
    Cui, Wen
    Wang, Lin
    Li, Zepeng
    Liu, Bo
    Lv, Hang
    Zou, Bo
    Cui, Tian
    Liu, Bingbing
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Department of Physics.
    In situ Raman and photoluminescence study on pressure-induced phase transition in C60 nanotubes2012In: Journal of Raman Spectroscopy, ISSN 0377-0486, E-ISSN 1097-4555, Vol. 43, no 6, p. 737-740Article in journal (Refereed)
    Abstract [en]

    Single crystalline C60 nanotubes having face-centered-cubic structure with diameters in the nanometer range were synthesized by a solution method. In situ Raman and photoluminescence spectroscopy under high pressure were employed to study the structural stabilities and transitions of the pristine C60 nanotubes. A phase transition, probably because of the orientational ordering of C60 molecules, from face-centered-cubic structure to simple cubic structure occurred at the pressure between 1.46 and 2.26 GPa. At above 20.41 GPa, the Raman spectrum became very diffuse and lost its fine structure in all wavenumber regions, and only two broad and asymmetry peaks initially centered at 1469 and 1570cm-1 were observed, indicating an occurrence of amorphization. This amorphous phase remained to be reversible until 31.1 GPa, and it became irreversible to the ambient pressure after the pressure cycle of 34.3 GPa was applied.

  • 122. Liu, Dedi
    et al.
    Yao, Mingguang
    Li, Quanjun
    Cui, Wen
    Zou, Bo
    Cui, Tian
    Lui, Bingbing
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Wågberg, Thomas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    High pressure and high temperature induced polymerization of C60 nanotubes2011In: CrystEngComm, ISSN 1466-8033, E-ISSN 1466-8033, Vol. 13, no 10, p. 3600-3605Article in journal (Refereed)
    Abstract [en]

    C60 nanotubes with outer diameters ranging from 400–800 nm were polymerized at 1.5 GPa, 573 K and 2.0 GPa, 700 K, respectively. Raman and photoluminescence spectroscopy were employed to characterize the polymeric phases of the treated samples. Both Raman and photoluminescence spectra showed that the C60 nanotubes transformed into the dimer and orthorhombic phases under the two different conditions, respectively. The photoluminescence peaks were tuned from visible to near infrared range. Comparative studies indicated that C60 nanotubes were more difficult to polymerize than bulk C60 material under the same conditions due to the nanoscale size effect in the C60 nanotubes.

  • 123. Liu, Dedi
    et al.
    Yao, Mingguang
    Wang, Lin
    Li, Quanjun
    Cui, Wen
    Liu, Bo
    Lui, Ran
    Zou, Bo
    Cui, Tian
    Liu, Bingbing
    Liu, Jing
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Wågberg, Thomas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Pressure-induced phase transitions of C70 nanotubes2011In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 115, no 18, p. 8918-8922Article in journal (Refereed)
    Abstract [en]

    Single crystalline C70 nanotubes having a face-centered-cubic (fcc) structure with diameters on a nanometer scale were synthesized by a facile solution method. In situ high pressure Raman spectroscopy and X-ray diffraction have been employed to study the structural stability and phase transitions of the pristine sample. We show that the molecular orientation-related phase transition from the fcc structure to a rhombohedral structure occurs at about 1.5 GPa, which is 1 GPa higher than in bulk C70. Also, the C70 molecules themselves are more stable in the nanotubes than in bulk crystals, manifested by a partial amorphization at 20 GPa. The crystal structure of C70 nanotubes could partially return to the initial structure after a pressure cycle above 30.8 GPa, and the C70 molecules were intact up to 43 GPa. The bulk modulus of C70 nanotubes is measured to be 50 GPa, which is twice larger than that of bulk C70.

  • 124.
    Lundberg, Bo
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Physics.
    Basal plane resistivity and phase diagram of HNO3 intercalated graphite in the range 130–320 K and 0–1.6 GPa1986In: Solid State Communications, ISSN 0038-1098, E-ISSN 1879-2766, Vol. 58, no 10, p. 747-751Article in journal (Refereed)
    Abstract [en]

    The basal plane resistivity varrho of stages 3–5 HNO3 intercalated graphite has been measured as a function of temperature T and pressure p in the range 130–320 K and 0–1.6 GPa (16 kbar). A contactless method was used. The phase boundary of the 250 K ordering transition at zero pressure was traced up to 320 K through the corresponding anomaly in varrho. The pressure dependence of varrho was strongly stage dependent, such that for stages 3, 4 and 5 the observed pressure coefficients (1/varrho)dvarrho/dp were approximately 0.08, −0.08, and −0.22 GPa−1, respectively, near zero pressure.

  • 125.
    Lundberg, Bo
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Physics.
    Resistivity of a composite conducting polymer as a function of temperature, pressure, and environment: Applications as a pressure and gas concentration transducer1986In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 60, no 3, p. 1074-1079Article in journal (Refereed)
    Abstract [en]

    The resistivity of a commercial carbon-filled composite conducting polymer (ET-Semicon[large-closed-square]) has been measured as a function of temperature between 80 and 400 K and under pressure up to 1.5 GPa (15 kbar). Large changes in resistivity were observed. The resistivity was also very sensitive to the presence of certain solvents and hydrocarbons. The results are explained as percolation effects caused by changes in volume due to pressure, thermal expansion, or dissolved solvents. The material studied is found to have a wide range of potential applications for pressure measurements and as a transducer for gas or liquid concentration.

  • 126.
    Lundberg, Bo
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Physics.
    Inganäs, Olle
    Lundström, Ingemar
    Salaneck, William R.
    Pressure-dependent electrical conductivity of polypyrrole1985In: Molecular Crystals and Liquid Crystals vol. 118: Proceedings of the International Conference on the Physics and Chemistry of Low-Dimensional Synthetic Metals (ISCM '84), Abano Terme 1984, 1985, p. 155-158Conference paper (Refereed)
    Abstract [en]

    The results of pressure dependent electrical conductivity measurements in polypyrrole are consistent with a simple extension of the variable-range-hopping model of electronic transport in disordered media.

  • 127.
    Lundberg, Bo
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Physics.
    Salaneck, William R.
    Pressure effects on electrical conductivities in intercalated graphite and doped polypyrrole1984In: Journal de Physique Colloque vol. 45: Supplément C8, Physics and Physicochemistry of Highly Condensed Matter; Proceedings of the XXIInd Meeting of the EHPRG, Aussois, Sept. 1984, 1984, p. 213-216Conference paper (Refereed)
    Abstract [en]

    We have measured the pressure dependence up to 2.5 GPa of the electrical resistance of the acceptor intercalated graphites CnFeCl3, CnSbF5, and CnHNO3. The slope of resistance versus pressure is approximately the same in all cases. Two different types of high pressure transitions are observed in CnSbF5 and CnHNO3. The results of electrical resistance measurements under pressure in polypyrrole are consistent with a simple extension of the variable-range-hopping model. We infer for this material that the density of states at the Fermi level increases with pressure.

  • 128.
    Lundin, Anders
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Soldatov, Alexander
    Umeå University, Faculty of Science and Technology, Physics.
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Physics.
    Compressibility and Structure of C701995In: Europhysics letters, ISSN 0295-5075, E-ISSN 1286-4854, Vol. 30, no 8, p. 469-474Article in journal (Refereed)
    Abstract [en]

    The compressibility of C70 has been investigated by means of direct piston and cylinder measurements in the temperature range 150 to 365 K and up to 1 GPa. At 296 and 343 K we find a very rapid change of volume with pressure below 0.15 GPa. We tentatively interpret this as a continuous molecular reorientation with pressure, probably resulting in a transformation from a mixture of face-centred cubic (f.c.c.) and rhombohedral (r.h.) phases to mainly pure r.h. phase. At 365 K as well as at 236 K and below we see no anomalies indicating any structural or rotational anomalies in the pressure range investigated. The zero-pressure bulk modulus decreases with increasing temperature, from 13.1 GPa at 185 K to 7.9 GPa at 365 K. Our volumetric measurements confirm a recently proposed phase diagram for C70.

  • 129.
    Lundin, Anders
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Soldatov, Alexander
    Umeå University, Faculty of Science and Technology, Physics.
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Physics.
    Compression properties and p-T phase diagrams of C60, C70, and C61D21996In: Fullerenes: Recent Advances in the Chemistry and Physics of Fullerenes and Related Materials, volume 3: Proceedings of the 189th ECS Meeting, Symposium Fullerenes: Chemistry, Physics, and New Directions VIII, Los Angeles 1996, 1996, p. 1138-1142Conference paper (Refereed)
    Abstract [en]

    We have measured the compression properties of C60, C70, and C61D2 in the range 0 - 1.2 GPa over large ranges in temperature (150 to 420 K). Our results for simple cubic (sc) C60 agree well with several recent studies using different methods, but data for face centered cubic (fcc) C60 and for C70 differ strongly between different groups. From our data we deduce the low-temperature orientational, rotational, and translational structural phase diagram of C60, but similar studies on C70 and C61D2 show that these materials have more complicated phase diagrams which cannot yet be mapped in detail.

  • 130.
    Lundin, Anders
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Soldatov, Alexander
    Umeå University, Faculty of Science and Technology, Physics.
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Physics.
    Thermophysical properties of C70 up to 1.2 GPa1995In: Science and Technology of Fullerene Materials: Materials Research Society Symposium Proceedings vol. 359, Pittsburgh: Materials Research Society , 1995, p. 555-560Conference paper (Refereed)
    Abstract [en]

    We have measured the thermal conductivity lambda and the compressibility of highly pure C70 in the range 90 to 450 K under pressures up to 1.2 GPa. Our results for the thermal conductivity indicate molecular rotation in C70 abobe 280 K at zero pressure. The phase boundary for the rotationally disordered phase has an approximate slope dT/dp ) 75 K/GPa. The bulk modulus B increases linearly with increasing p above 0.1 GPa, with an extrapolated zero pressure value at 296 K of B(0) = 8.3 GPa. Unexpected anomalies are found in both B and lambda near 100 MPa, and we tentatively suggest that orientational ordering is responsible.

  • 131.
    Lundin, Anders
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Soldatov, Alexander
    Umeå University, Faculty of Science and Technology, Physics.
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Physics.
    Strongin, R.M.
    Brard, L.
    Fischer, John E.
    Smith, III, A.B.
    Compressibility of C61D2 up to 1 GPa in the temperature range 175 - 345 K1996In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 34, no 9, p. 1119-1121Article in journal (Refereed)
    Abstract [en]

    We have measured the bulk modulus K for C61D2 up to 1 GPa in the temperature range 175–343 K. For face-centered cubic C61D2 above 290 K, we find an anomalously low value for K below about 0.15 GPa, possibly indicating pressure-induced changes in the structure. The (extrapolated) zero-p bulk modulus K(0) decreases with increasing T from 6.7 GPa at 175 K to 5.2 GPa at 343 K. A comparison with hypothetical expanded f.c.c. C60 with the same lattice constant shows that K(0) values are similar, indicating that the main intermolecular interactions are still between molecular bellies, not the sidegroups.

  • 132.
    Lundin, Anders
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Physics.
    Compressibility of C60 between 150 and 335 K and up to 1 GPa1994In: Europhysics letters, ISSN 0295-5075, E-ISSN 1286-4854, Vol. 27, no 6, p. 463-466Article in journal (Refereed)
    Abstract [en]

    The bulk modulus B of C60 has been measured in the range 150-335 K and up to 1 GPa, for the first time in the f.c.c. rotationally disordered phase, through the f.c.c. → s.c. transition, and in the s.c. phase. At 298 K we find B values of 8.8 (s.c.) and 6.8 GPa (f.c.c.), significantly lower than those found in previous studies. At the transition B decreases with decreasing V, which is probably an effect of orientational ordering on intermolecular interactions.

  • 133.
    Lundin, Anders
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Physics.
    Compressibility of C60 in the temperature range 150 - 335 K up to a pressure of 1 GPa1996In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 53, no 13, p. 8329-8336Article in journal (Refereed)
    Abstract [en]

    We have measured the volume of nominally 99.9% pure C60 as a function of pressure (p) in both the fcc and sc phases up to 1 GPa over the temperature range 150 to 335 K using a highly accurate piston-and-cylinder technique. At zero pressure, the room-temperature bulk modulus B(0) is 6.8 GPa for the fcc phase and about 8.7–9.5 GPa for the sc phase. For the latter phase, B(0) increases strongly with decreasing temperature to 10.4 GPa at 152 K and for both phases B increases rapidly with increasing pressure. The fcc→sc transformation is always smeared over large ranges in p. Surprisingly, above 200 MPa B is lower in the sc phase than in the fcc phase, which we explain as arising from molecular reorientation with increasing pressure. The formation of a mainly ‘‘hexagon’’-oriented, ordered phase above 0.6 GPa at low T gives rise to observable anomalies in B(p).

  • 134.
    Lundin, Anders
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Physics.
    Bäckström, Gunnar
    Umeå University, Faculty of Science and Technology, Physics.
    A piston-and-cylinder device for compressibility studies on polymers and other "soft" materials1994In: High Pressure Research volume 13, issue 1-3: Proceedings of the XXXIst Annual Meeting of the European High Pressure Research Group, Belfast 1993, Yverdon: Gordon and Breach , 1994, p. 141-145Conference paper (Refereed)
    Abstract [en]

    We describe an all-steel piston-and-cylinder device for pVT studies on “soft” materials, including liquids, in the range 100-450 K and 0-1.5 GPa. The internal diameter is 15 mm with sample lengths between 10 and 50 mm. Piston displacements are measured to within 0.1 μm using differential transformer transducers. Pressure is calculated from force per unit area and the deformation of pistons and cylinder under pressure are taken into account. The inaccuracy in ΔV/V is less than 0.5%. Experimental data are shown for indium and urea.

  • 135.
    Lundin, Anders
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Physics.
    Skoglund, Peter
    Umeå University, Faculty of Science and Technology, Applied Physics and Electronics.
    Fransson, Åke
    Umeå University, Faculty of Science and Technology, Applied Physics and Electronics.
    Pettersson, Sune
    Umeå University, Faculty of Science and Technology, Physics.
    Compressibility, specific heat capacity, and Grüneisen parameter for C60/C701992In: Solid State Communications, ISSN 0038-1098, E-ISSN 1879-2766, Vol. 84, no 9, p. 879-883Article in journal (Refereed)
    Abstract [en]

    We have measured the specific heat capacity cp of C60/C70 between 110 and 310 K and its compressibility κ up to 1.1 GPa (11 kbar) at 293 K, a range in t and p which overlaps reported ranges of stability of both the rotationally disordered high T, low p fcc phase and the low T high p orientationally ordered sc phase. No sharp anomaly is observed in cp at the transition. The bulk modulus B near p = 0 was 8.4 GPa, rapidly increasing to about 16 GPa near 1 GPa. For our data, the intermolecular forces could be modeled by either a Lennard-Jones or a Born-Mayer potential, but this was not the case if literature data for compression vs. p were used.

  • 136. Ma, Honglei
    et al.
    Zhang, Xuemei
    Liu, Bingbing
    Li, Quanjun
    Zeng, Qifeng
    Yu, Shidan
    Zou, Bo
    Cui, Tian
    Zou, Guangtian
    Liu, Zhenxian
    Wågberg, Thomas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Noreus, Dag
    Synchrotron X-ray diffraction and infrared spectroscopy studies of C60H18 under high pressure2010In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 1, no 4, p. 714-719Article in journal (Refereed)
    Abstract [en]

    In situ high-pressure angle-dispersive synchrotron X-ray diffraction and high-pressure mid-infrared (IR) spectrum measurements of C60H18 were carried out up to 32 and 10.2 GPa, respectively. Our diffraction data indicated that the fcc structure of C60H18 was stable up to 32 GPa. The bulk modulus B0 was determined to be 21 ± 1.16 GPa, about 40% higher than that of C60. The C−H vibrations still existed up to 10.2 GPa, and the vibrational frequencies decreased with increasing pressure. IR-active vibrational frequencies and their corresponding eigenvectors of C60H18 were simulated by DMOL3. The effects of the hydrogen atoms attached to the fullerene molecular cage on the stability of the structure under high pressure are discussed.

  • 137.
    Makarova, Tatiana L
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Han, K.-H.
    Umeå University, Faculty of Science and Technology, Physics.
    Esquinazi, P
    da Silva, R.R.
    Kopelevich, Yakov
    Zakharova, I.B.
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Physics.
    Magnetism in photopolymerized fullerenes2003In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 41, no 8, p. 1575-1584Article in journal (Refereed)
    Abstract [en]

    The phototransformation of bulk C-60 and laser- and electron-beam treatment of C-60 films in air changes their magnetic properties. Nonlinear magnetization is observed only for samples irradiated in the presence of oxygen, while, in the case of pressure-polymerized C-60, oxygen adversely affects the magnetic properties. The contrasting roles of oxygen in these processes are discussed. Magnetic force microscopy shows that laser- and electron-beam irradiation of fullerene films produces magnetic images which are highly correlated with the topographic images.

  • 138.
    Makarova, Tatiana L
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Liu, Bingbing
    Umeå University, Faculty of Science and Technology, Physics.
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Physics.
    AC susceptibility of some neutral C60 polymers2001In: Electronic Properties of Novel Materials - Science and Technology of Molecular Nanostructures: Proceedings of the XV International Winter School on Electronic Properties of Novel Materials, Kirchberg 2001, American Institute of Physics , 2001, p. 57-60Conference paper (Refereed)
    Abstract [en]

    We have measured the temperature dependence of the magnetic susceptibility of photopolymerized and pressure-polymerized neutral C60 fullerenes. The data on C60 are diamagnetic. The observed magnetic response of both types of polymers is paramagnetic.

  • 139.
    Makarova, Tatiana L
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Scharff, Peter
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Physics.
    Narymbetov, B.
    Kobayashi, H.
    Tokumoto, M.
    Davydov, V.A.
    Rakhmanina, A.V.
    Kashevarova, L.S.
    Anisotropic metallic properties of highly-oriented rhombohedral C60 polymer.2001In: Synthetic Metals vol. 121: Proceedings of the International Conference on the Science and Technology of Synthetic Metals (ICSM2000), Gastein 2000, Amsterdam: Elsevier B.V. , 2001, p. 1099-1100Conference paper (Refereed)
    Abstract [en]

    The pure rhombohedral phase of C60 polymer displays highly anisotropic electrical properties. Conductivity in the polymerized (001) planes exhibits a metal-insulator transition and shows the features of 2D weak localization. Anisotropy ratio is temperature-dependent and reaches 10_6. Dysonian ESR lineshape is consistent with the metallic nature of the samples.

  • 140.
    Makarova, Tatiana L
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Physics.
    Höhne, Roland
    Esquinazi, Pablo
    Kopelevich, Yakov
    Scharff, Peter
    Davydov, Valerii A.
    Kashevarova, Ludmila S.
    Rakhmaninova, Aleksandra V.
    Magnetic Carbon2001In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 413, no 6857, p. 716-718Article in journal (Refereed)
    Abstract [en]

    Paper retracted.

  • 141.
    Makarova, Tatiana L
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Physics.
    Kopelevich, Yakov
    Magnetism in C60 induced by polymerization2002In: Fullerenes vol. 12: The Exciting World of Nanocages and Nanotubes: Proceedings of the 201st ECS Meeting, Symposia V1-V9: Fullerenes, Nanotubes, and Carbon Nanoclusters, Pennington: The Electrochemical Society , 2002, p. 664-678Conference paper (Refereed)
  • 142.
    Makarova, Tatiana L
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Physics.
    Kopelevich, Yakov
    Structural studies of magnetic polymerized fullerenes2003In: Synthetic Metals volume 137: Proceedings of the International Conference on Science and Technology of Synthetic Metals, Shanghai 2002, Amsterdam: Elsevier B.V. , 2003, p. 1335-1337Conference paper (Refereed)
    Abstract [en]

    X-ray and Raman measurements have been performed on samples of polymerized fullerenes which show weak ferromagnetism. For pressure-polymerized fullerenes, ferromagnetic features are observed in a narrow temperature range very close to the limit of stability of the cages. Raman spectra show that the type of polymerization is probably of less importance. Strong structural inhomogeneity of the samples suggests that the magnetic phase forms a minority phase in a non-magnetic matrix.

  • 143.
    Makarova, Tatiana L
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Scharff, Peter
    Gaevski, M.E.
    Olsson, Eva
    Davydov, V.A.
    Rakhmanina, A.V.
    Kashevarova, L.S.
    Electrical properties of two-dimensional fullerene matrices2001In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 39, no 14, p. 2203-2209Article in journal (Refereed)
    Abstract [en]

    The electrical properties of two-dimensionally polymerized C60 fullerenes were studied. Fullerene matrices consisting of randomly oriented domains are compared to the highly-oriented rhombohedral phase. The conductivity of the randomly oriented polymers obeys the Arrhenius law and can be described in a multiple trapping model. The oriented phase of polymeric C60 shows a distinct anisotropy in the electrical properties with a metallic-like in-plane conductivity at high temperatures.

  • 144.
    Makarova, Tatiana L
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Wågberg, Thomas
    Umeå University, Faculty of Science and Technology, Physics.
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Physics.
    Agafonov, V.
    Davydov, V.A.
    Rakhmanina, A.V.
    Kashevarova, L.S.
    Electrical properties of the rhombohedral C60 polymers1999In: Fullerenes: Recent Advances in the Chemistry and Physics of Fullerenes and Related Materials, vol. 7: Proceedings of the Symposium "Fullerenes: Chemistry, Physics, and New Directions XII", 195th Meeting of the Electrochemical Society, Seattle 1999, Pennington, NJ: The Electrochemical Society , 1999, p. 628-639Conference paper (Refereed)
    Abstract [en]

    Electrical properties of polymerized fullerenes C60 are governed by the type of polymerization which is in turn determined by the initial (P or H) orientation of molecules, the pressure and the temperature of polymerization. The mixed tetragonal - rhombohedral polymerized structure shows a semiconductor-like behavior. An increase in the polymerization temperature results in a decrease in the activation energy and an increase in conductivity. The conductivity prefactor and the activation energy are interconnected by the Meyer-Neldel rule. The pure rhombohedral phase shows highly anisotropic electrical properties. The conductivity in the polymerized (111) planes exhibits a metal-insulator transition and shows the features of 2D weak localization.

  • 145.
    Makarova, Tatiana L
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Wågberg, Thomas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Zhu, Xiaomei
    Nyeanchi, Emmanuel B.
    Gaevski, M.E.
    Olsson, Eva
    Agafonov, V.
    Davydov, V.A.
    Rakhmaninova, A.V.