| 1. |
- Xing, K. Z., et al.
(författare)
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The electronic and geometric structures of neutral and potassium-doped poly[3-(4-octylphenyl)thiophene] studied by photoelectron spectroscopy
- 1996
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Ingår i: Synthetic metals. - : Elsevier. - 0379-6779 .- 1879-3290. ; 76:1-3, s. 263-267
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Tidskriftsartikel (refereegranskat)abstract
- The electronic and geometric structures of poly [3-(4-octylphenyl)thiophene] have been studied by X-ray and ultraviolet photoelectron spectroscopy (XPS and UPS, respectively). Thermochromic effects, and new charge induced states generated by potassium doping, have been observed by direct UPS measurements. The experimental results are in very good agreement with the results of theoretical quantum chemical calculations performed with the Austin Model 1 semi-empirical model and the valence-effective Hamiltonian pseudo-potential model.
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| 2. |
- Xing, K. Z., et al.
(författare)
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The electronic structure of neutral and alkali metal-doped poly[3-(4-octylphenyl)thiophene] studied by photoelectron spectroscopy
- 1996
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Ingår i: Synthetic metals. - : Elsevier. - 0379-6779 .- 1879-3290. ; 80:1, s. 59-66
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Tidskriftsartikel (refereegranskat)abstract
- The electronic structure of poly [3-(4-octylphenyl)thiophene] (POPT) has been studied by ultraviolet photoelectron spectroscopy (UPS) and X-ray photoelectron spectroscopy (XPS), as well as by quantum chemical calculations. Both temperature-dependent effects on the electronic structure of the neutral system, as well as the generation of new electronic states induced by doping with alkaline metals, have been observed. The experimental results are in good agreement with the results of the quantum chemical calculations.
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| 3. |
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| 4. |
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| 5. |
- Hellberg, J, et al.
(författare)
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New monomers for polythiophenes
- 1997
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Ingår i: Synthetic metals. - 0379-6779 .- 1879-3290. ; 84
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Tidskriftsartikel (refereegranskat)
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| 6. |
- Johansson, Mats P., 1965-
(författare)
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Growth and microstructure of reactive sputter deposited boron nitride : carbon (BN:C) thin films
- 1995
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Growth, microstructure and mechanical properties of boron nitride: carbon (BN:C) have been studied in films prepared by reactive r.f. diode sputter deposition as well as by reactive unbalanced d.c. magnetron (UBM) sputter deposition of low resistivity boron carbide (B4C) targets. Due to the fäet that d.c. glow discharges offers a better control of the important growth parameters such as particle flux and energy distribution in both neutral and ionized states at the substrate as compared to r.f. methods, fundamental growth and plasma studies were in some detail performed in the UBM sputtering system.Films were prepared with three characteristic phase compositions; cubic c-BN:C, hexagonal (turbostratic-like) h-BN:C and a mixtures of these on Si (001) substrates. The same phase compositions were obtained in both deposition techniques. While keeping the B/N ratio close to unity, the formation of BN:C phases were mainly correlated to the energy and flux of impinging ions towards the negatively d.c. biased substrate. A c-BN:C phase formation was typically found in mixed c-BN:C and h-BN:C films prepared at high ion-to-neutral flux ratios (UBM: Ji/Jn ~24), within a narrow range in ion energies (UBM: 85 eV < Ei < 135 eV) and at low process temperatures <250 °C. However, almost single phase c-BN:C (~80 % of sp3-bonded B-N) was obtained at deposition conditions of high ion flux (UBM: Ji/Jn ~24) and low ion energy (UBM: Ei = 110 eV) whereas films deposited at much lower ion energy or at a lower ion fluxes contained exclusively h-BN:C. Also, c-BN:C films revealed a BN:C film phase evolution sequence from an initial amorphous BN:C layer followed by a highly oriented h-BN:C layer with the c-axis parallel to the film surface, to a c-BN:C layer exhibiting a (110)preferred orientation. Furthermore, as-deposited films contained 5 - 20 at% of C that was found to decrease with increasing volume fraction of c-BN:C and also with increasing J/Jn. Chemical sputtering of volatile CN species is suggested for the reduction of C in BN:C films. Nevertheless, the C in c-BN:C films is mainly present as C-C and B-C bonds.Unnoticed the presence of C, cubic phase BN:C films are shown to be formed at deposition conditions not included in the present models of c-BN growth. For example, in terms of momentum transfer, values of 200 - 250 (eV emu)% have been reported to be required for the synthesis of c-BN whereas in this study an order of magnitude higher values were found. The results thus point at an extended deposition window for cubic phase formation, with potential for using further reduced ion energies such that intrinsic compressive stress in BN can be minimized.Finally, the mechanical properties of randomly- and highly-oriented h-BN:C as well as of c-BN:C films were studied and compared to the uncoated Si substrate. Although all coated substrates showed an increased stiffness, the maybe most interesting properties were found in the highly oriented h-BN:C films with the c-axis parallel to the film surface. These films showed a predominantly elastic behaviour exhibiting an elastic recovery as high as 82% indicating high hardness values. The improved hardness and elasticity may be explained by the apparent microstructure with buckling of the hexagonal basal planes. This structure is proposed to correspond to a three dimensional strongly covalently bonded network of BN:C, similar to what has been reported for CNx films.
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| 7. |
- Johansson, Mats P., 1965-
(författare)
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Reactive Sputtering of Cubic-Phase BN:C and Nanostructured B-N-C Films : Growth, Microstructure, and Mechanical Properties
- 1998
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Synthesis, structure, and mechanical property related issues in the carbon-containing boron nitride (BN:C) system have been studied. Magnetron sputtering, comprising a B4C target in mixed Ar-N2 discharges and deposition parameters of low ion energy, high ion-to-neutral flux ratio, and substrate temperatures <350 °C were employed for growth. Transmission electron microscopy and electron energy loss spectroscopy (EELS) served as the mainstructure evaluation tools, while nanoindentation experiments were used for mechanical property evaluation.Studies of the growth process as a function of partial pressure of nitrogenin the gas mixture revealed first a saturation of the nitrogen on the target whereas at slightly higher PN2 values the overall system is nitrided. This effect was ascribed to the relatively low enthalpy of compound formation of BN. Furthermore, by the use of an internal solenoid coil, the plasma density and hence the ion flux impinging on the growing film could be increased by more than one order of magnitude, resulting in a maximum ion-to-condensing atom flux ratio of ~24. At these conditions, i.e., with a saturation of the nitrogenin corporation frequency on the growth surface and a high flux ratio, growth of cubic-phase c-BN:C was demonstrated at ion-energies as low as 110 eV. This opens a new process window for c-BN phase formation at conditions not accounted for in the prevailing mechanistic models of momentum transfer.The system exhibits a phase evolution sequence of textured (hexagonal)h-BN:C prior to the nucleation and growth of crystallographically oriented cBN:C. The h-BN:C material obtained at intermediate flux-ratios and floating potential exhibits interesting mechanical properties of extreme elasticity and a structure consisting of curved and buckled basal planes similar to what previously have been reported in fullerene-like CNx films. Growth of CNx/BN:C multilayers was demonstrated by sequential sputtering from B4C and graphite targets, respectively, in mixed Ar-N2 atmospheres. They exhibit similar structure as the single-layer films, but do offer additional means for mechanical property design including strengthening over the single-layer compounds.Results are presented to demonstrate the possibility of using sputter deposition technique to synthesize CNx and template-synthesized B-N-C tubular nanostructures, which promises important advances to tailor the structure (dimension and shape) and number density of various types of nanostructures.Finally, an immiscibility between BN and C(N) in magnetron sputtered graphitic layered B-N-C materials was established by EELS. Nitrogen-rich films exhibited predominantly B-N and C-N type of bonds whereas films prepared with a much lower nitrogen concentration also revealed B-C bonds. Thus, magnetron discharge conditions at low temperature is a promising approach to produce B-N, C-N and B-C type of bonds for controlling the chemical composition of nanostructures in the B-N-C ternary system.
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| 10. |
- Sundin, Anders, et al.
(författare)
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PET and parathyroid L-[carbon-11]methionine accumulation in hyperparathyroidism
- 1996
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Ingår i: Journal of Nuclear Medicine. - 0161-5505 .- 1535-5667. ; 37:11, s. 1766-1170
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Tidskriftsartikel (refereegranskat)abstract
- The study was designed to characterize L-[methyl-11 C]methionine accumulation in abnormal parathyroid tissues of hyperparathyroidism (HPT).METHODS:Thirty-four patients with primary (n = 32) or secondary HPT were investigated with PET before primary or reoperative (n = 25) parathyroid surgery. Parathyroid 11C-methionine accumulation was analyzed for integrated uptake values in defined tissue volumes standardized for the injected dose and body weight (SUV), four contiguous pixels of maximal accumulation (SUVhs), SUV multiplied by area of region of interest (SUVr) and by the excised tissue weight (SUVw). Transport rate constants (slope, slopehs) were calculated according to Patlak's formula using plasma 11C activity corrected for 11C-methionine metabolites.RESULTS:True-positive localization was achieved in 85% of patients in whom 81% of the excised parathyroid lesions were visualized; no false-positive results were obtained. Corresponding proportions were 59% and 57% for CT and 55% and 52% for ultrasound, respectively. In the true-positive cases, parathyroid SUV, SUVhs and transport rate constants were consistently higher (p < 0.01) than in the thyroid, pharynx-esophagus, neck muscle and apical lung. Parathyroid SUV, SUVhs and SUVr increased with intact serum parathyroid hormone and calcium values (p = 0.0001-0.031), and weight of the excised tissue correlated with SUV and SUVhs (p = 0.024, 0.044). Parathyroid SUVhs varied strongly with the transport rate constants (p = 0.0008), and SUVr as well as s-calcium values differed significantly between parathyroid adenomas (n = 11), chief cell hyperplasias (n = 13), inadvertent implants (n = 3) and parathyroid cancers (n = 3).CONCLUSION:Carbon-11-methionine PET has potential application in preoperative localization and metabolic characterization of abnormal parathyroid tissues in human HPT.
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