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Sökning: WFRF:(Braun F) > Linköpings universitet

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1.
  • Crivillers, N, et al. (författare)
  • Photoinduced work function changes by isomerization of a densely packed azobenzene-based SAM on Au: a joint experimental and theoretical study
  • 2011
  • Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry. - 1463-9076 .- 1463-9084. ; 13:32, s. 14302-14310
  • Tidskriftsartikel (refereegranskat)abstract
    • Responsive monolayers are key building blocks for future applications in organic and molecular electronics in particular because they hold potential for tuning the physico-chemical properties of interfaces, including their energetics. Here we study a photochromic SAM based on a conjugated azobenzene derivative and its influence on the gold work function (Phi(Au)) when chemisorbed on its surface. In particular we show that the Phi(Au) can be modulated with external stimuli by controlling the azobenzene trans/cis isomerization process. This phenomenon is characterized experimentally by four different techniques, kelvin probe, kelvin probe force microscopy, electroabsorption spectroscopy and ultraviolet photoelectron spectroscopy. The use of different techniques implies exposing the SAM to different measurement conditions and different preparation methods, which, remarkably, do not alter the observed work function change (Phi(trans)-Phi(cis)). Theoretical calculations provided a complementary insight crucial to attain a deeper knowledge on the origin of the work function photo-modulation.
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2.
  • Sarakinos, Kostas, et al. (författare)
  • On the phase formation of sputtered hafnium oxide and oxynitride films
  • 2010
  • Ingår i: Journal of Applied Physics. - : American Institute of Physics (AIP). - 0021-8979 .- 1089-7550. ; 108:1, s. 014904-
  • Tidskriftsartikel (refereegranskat)abstract
    • Hafnium oxynitride films are deposited from a Hf target employing direct current magnetron sputtering in an Ar-O(2)-N(2) atmosphere. It is shown that the presence of N(2) allows for the stabilization of the transition zone between the metallic and the compound sputtering mode enabling deposition of films at well defined conditions of target coverage by varying the O(2) partial pressure. Plasma analysis reveals that this experimental strategy facilitates control over the flux of the O(-) ions which are generated on the oxidized target surface and accelerated by the negative target potential toward the growing film. An arrangement that enables film growth without O(-) ion bombardment is also implemented. Moreover, stabilization of the transition sputtering zone and control of the O(-) ion flux without N(2) addition is achieved employing high power pulsed magnetron sputtering. Structural characterization of the deposited films unambiguously proves that the phase formation of hafnium oxide and hafnium oxynitride films with the crystal structure of HfO(2) is independent from the O(-) bombardment conditions. Experimental and theoretical data indicate that the presence of vacancies and/or the substitution of O by N atoms in the nonmetal sublattice favor the formation of the cubic and/or the tetragonal HfO(2) crystal structure at the expense of the monoclinic HfO(2) one.
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3.
  • Weismuller, T. J., et al. (författare)
  • Patient Age, Sex, and Inflammatory Bowel Disease Phenotype Associate With Course of Primary Sclerosing Cholangitis
  • 2017
  • Ingår i: Gastroenterology. - : Elsevier BV. - 0016-5085 .- 1528-0012. ; 152:8, s. 1975-1984.e8
  • Tidskriftsartikel (refereegranskat)abstract
    • BACKGROUND & AIMS: Primary sclerosing cholangitis (PSC) is an orphan hepatobiliary disorder associated with inflammatory bowel disease (IBD). We aimed to estimate the risk of disease progression based on distinct clinical phenotypes in a large international cohort of patients with PSC. METHODS: We performed a retrospective outcome analysis of patients diagnosed with PSC from 1980 through 2010 at 37 centers in Europe, North America, and Australia. For each patient, we collected data on sex, clinician-reported age at and date of PSC and IBD diagnoses, phenotypes of IBD and PSC, and date and indication of IBD-related surgeries. The primary and secondary endpoints were liver transplantation or death (LTD) and hepatopancreatobiliary malignancy, respectively. Cox proportional hazards models were applied to determine the effects of individual covariates on rates of clinical events, with time-to-event analysis ascertained through Kaplan-Meier estimates. RESULTS: Of the 7121 patients in the cohort, 2616 met the primary endpoint (median time to event of 14.5 years) and 721 developed hepatopancreatobiliary malignancy. The most common malignancy was cholangiocarcinoma (n = 594); patients of advanced age at diagnosis had an increased incidence compared with younger patients (incidence rate: 1.2 per 100 patient-years for patients younger than 20 years old, 6.0 per 100 patient-years for patients 21-30 years old, 9.0 per 100 patient-years for patients 31-40 years old, 14.0 per 100 patient-years for patients 4150 years old, 15.2 per 100 patient-years for patients 51-60 years old, and 21.0 per 100 patient-years for patients older than 60 years). Of all patients with PSC studied, 65.5% were men, 89.8% had classical or large-duct disease, and 70.0% developed IBD at some point. Assessing the development of IBD as a time-dependent covariate, Crohn's disease and no IBD (both vs ulcerative colitis) were associated with a lower risk of LTD (unadjusted hazard ratio [HR], 0.62; P <.001 and HR, 0.90; P =.03, respectively) and malignancy (HR, 0.68; P =.008 and HR, 0.77; P =.004, respectively). Small-duct PSC was associated with a lower risk of LTD or malignancy compared with classic PSC (HR, 0.30 and HR, 0.15, respectively; both P <.001). Female sex was also associated with a lower risk of LTD or malignancy (HR, 0.88; P =.002 and HR, 0.68; P <.001, respectively). In multivariable analyses assessing the primary endpoint, small-duct PSC characterized a low-risk phenotype in both sexes (adjusted HR for men, 0.23; P <.001 and adjusted HR for women, 0.48; P =.003). Conversely, patients with ulcerative colitis had an increased risk of liver disease progression compared with patients with Crohn's disease (HR, 1.56; P <.001) or no IBD (HR, 1.15; P =.002). CONCLUSIONS: In an analysis of data from individual patients with PSC worldwide, we found significant variation in clinical course associated with age at diagnosis, sex, and ductal and IBD subtypes. The survival estimates provided might be used to estimate risk levels for patients with PSC and select patients for clinical trials.
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4.
  • Friedlein, Rainer, et al. (författare)
  • Surface-induced vertical alignment of self-assembled supramolecular columns of large polycyclic aromatic hydrocarbons and porphyrins
  • 2004
  • Ingår i: Synthetic metals. - : Elsevier BV. - 0379-6779 .- 1879-3290. ; 147:01-Mar, s. 79-83
  • Tidskriftsartikel (refereegranskat)abstract
    • Ordered films of polycyclic aromatic hydrocarbons (PAHs) and porphyrins with functional (e.g. thiophene) side-groups are good candidates for (opto-)electronic applications where fast charge separation and transport are required. Such highly ordered thin films of PAHs, including discotic hexa-peri-hexabenzocoronene (HBC) and C-132-C-16,C-4, as well as brominated functionalized porphyrin molecules have been grown from solutions on semi-metallic molybdenum disulfide substrates and characterized by angle-resolved valence band photoelectron spectroscopy. A vertical growth of self-assembled supramolecular columns perpendicular to the basal plane of the substrate along with their lateral ordering on the surface has been achieved. Annealing made it possible to increase the structural order in the HBC columns, with molecules positioned at a regular offset from the columnar axis. This permitted the formation of extended pi-electronic states with a bandwidth of at least 0.1-0.2 eV at room temperature. (C) 2004 Elsevier B.V. All rights reserved.
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5.
  • Gorgoi, M, et al. (författare)
  • The high kinetic energy photoelectron spectroscopy facility at BESSY progress and first results
  • 2009
  • Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 601:1-2, s. 48-53
  • Tidskriftsartikel (refereegranskat)abstract
    • Photoelectron spectroscopy at high kinetic energy is a research field that receives an increasing interest due to the possibility of studying bulk properties of materials and deeply buried interfaces. Recently the high kinetic energy electron (HIKE) spectroscopy facility at BESSY in Berlin has become operative at the bending magnet beamline KMC-1. The first results show very good performance. Electron spectra have been recorded using X-ray energies from 2 keV up to 12 keV. Using back-scattering conditions in the crystal monochromator, very high-resolution has been achieved for photon energies around 2, 6 and 8 keV. In the latter case, spectra with a resolving power from the monochromator of >= 80 000 have been achieved and it has been possible to perform electron spectroscopy with resolving power of >= 60 000, yielding a total instrument resolution of about 150 meV as determined directly from spectra. This paper describes the facility and reports some of the first results. (C) 2009 Elsevier B.V. All rights reserved.
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6.
  • Hutton, B F, et al. (författare)
  • Reducing the influence of spatial resolution to improve quantitative accuracy in emission tomography : A comparison of potential strategies
  • 2006
  • Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 569:2 SPEC. ISS., s. 462-466
  • Tidskriftsartikel (refereegranskat)abstract
    • The goal of this paper is to compare strategies for reducing partial volume effects by either minimizing the cause (i.e. improving resolution) or correcting the effect. Correction for resolution loss can be achieved either by modelling the resolution for use in iterative reconstruction or by imposing constraints based on knowledge of the underlying anatomy. Approaches to partial volume correction largely rely on knowledge of the underlying anatomy, based on well-registered high-resolution anatomical imaging modalities (CT or MRI). Corrections can be applied by considering the signal loss that results by smoothing the high-resolution modality to the same resolution as obtained in emission tomography. A physical phantom representing the central brain structures was used to evaluate the quantitative accuracy of the various strategies for either improving resolution or correcting for partial volume effects. Inclusion of resolution in the reconstruction model improved the measured contrast for the central brain structures but still underestimated the true object contrast (∼0.70). Use of information on the boundaries of the structures in conjunction with a smoothing prior using maximum entropy reconstruction achieved some degree of contrast enhancement and improved the noise properties of the resulting images. Partial volume correction based on segmentation of registered anatomical images and knowledge of the reconstructed resolution permitted more accurate quantification of the target to background ratio for individual brain structures. © 2006 Elsevier B.V. All rights reserved.
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7.
  • Lewin, Erik, et al. (författare)
  • On the origin of a third spectral component of C1s XPS-spectra for nc-TiC/a-C nanocomposite thin films
  • 2008
  • Ingår i: Surface & Coatings Technology. - : Elsevier BV. - 0257-8972 .- 1879-3347. ; 202:15, s. 3563-3570
  • Tidskriftsartikel (refereegranskat)abstract
    • X-ray photoelectron spectroscopy (XPS) spectra of sputter-etched nc-TiC/a-C nanocomposite thin films published in literature show an extra feature of unknown origin in the C1s region. This feature is situated between the contributions of carbide and the carbon matrix. We have used high kinetic energy XPS (HIKE-XPS) on magnetron-sputtered nc-TiC/a-C thin films to show that this feature represents a third chemical environment in the nanocomposites, besides the carbide and the amorphous carbon. Our results show that component is present in as-deposited samples, and that the intensity is strongly enhanced by Ar+-ion etching. This third chemical environment may be due to interface or disorder effects. The implications of these observations on the XPS analysis of nanocomposites are discussed in the light of overlap problems for ternary carbon based systems.
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8.
  • Marciniak Braun, Slawomir, et al. (författare)
  • Light Induced Damage in Poly(3,4-ethylenedioxythiophene) and its Derivatives Studied by Photoelectron Spectroscopy
  • 2004
  • Ingår i: Synthetic metals. - : Elsevier. - 0379-6779 .- 1879-3290. ; 141:1-2, s. 67-73
  • Tidskriftsartikel (refereegranskat)abstract
    • Poly(3,4-ethylenedioxythiophene), usually known as PEDOT, and derivatives have attracted significant interest because of their high electrical conductivity. This electric property, however, deteriorates upon exposure to solar radiation. X-ray photoelectron spectroscopy (XPS) has been used to study the UV-light-induced chemical changes in doped PEDOT, as well as in both neutral and doped forms of its alkylated derivative—PEDOT-C14H29. Analysis of the XPS data indicates an oxidation of the sulfur in the thiophene ring. Apparently, photo-oxidation leads to the formation of sulfon groups, SO2, resulting in a disruption of π-conjugation in PEDOT, which there by diminishes the conductivity of the organic layer. This hypothesis is supported by the results of a study of model molecules for pristine and the oxidized PEDOT unit: 3,4 ethylenedioxythiophene (EDOT) and 3,4 ethylenedioxythiophene and S-dioxide (EDOT-SO2), respectively.
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9.
  • Sarakinos, Kostas, et al. (författare)
  • Ionized physical vapor deposited Al(2)O(3) films : Does subplantation favor formation of alpha-Al(2)O(3)?
  • 2010
  • Ingår i: Physica Status Solidi. Rapid Research Letters. - : Wiley-VCH Verlag Berlin. - 1862-6254 .- 1862-6270. ; 4:7, s. 154-156
  • Tidskriftsartikel (refereegranskat)abstract
    • The broad energy distributions of the condensing particles typically encountered in ion assisted vapor deposition techniques are often a drawback when attempting to understand the effect of the energetic bombardment on the film properties. In the current study, a monoenergetic Al beam generated by a filtered cathodic arc discharge is employed for the deposition of alumina (Al(2)O(3)) films at well defined AI ion energies between 4 eV and 200 eV at a substrate temperature of 720 degrees C. Structural analysis shows that Al energies of 40 eV or larger favor the formation of the thermodynamically stable zeta-Al(2)O(3) phase at the expense of other metastable Al(2)O(3) polymorphs. The well defined ion energies are used as input for Monte-Carlo based simulations of the ion surface interactions. The results of these simulations reveal that the increase of the Al(+) ion energy leads to an increase in the fraction of ions subplanted into the growing film. These findings underline the previously not considered role of subsurface processes on the phase formation of ionized physical vapor deposited Al(2)O(3) films.
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10.
  • Zarechnaya, E Yu, et al. (författare)
  • Superhard Semiconducting Optically Transparent High Pressure Phase of Boron
  • 2009
  • Ingår i: PHYSICAL REVIEW LETTERS. - 0031-9007. ; 102:18, s. 185501-
  • Tidskriftsartikel (refereegranskat)abstract
    • An orthorhombic (space group Pnnm) boron phase was synthesized at pressures above 9 GPa and high temperature, and it was demonstrated to be stable at least up to 30 GPa. The structure, determined by single-crystal x-ray diffraction, consists of B-12 icosahedra and B-2 dumbbells. The charge density distribution obtained from experimental data and ab initio calculations suggests covalent chemical bonding in this phase. Strong covalent interatomic interactions explain the low compressibility value (bulk modulus is K-300=227 GPa) and high hardness of high-pressure boron (Vickers hardness H-V=58 GPa), after diamond the second hardest elemental material.
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