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  • 1.
    Aslandukov, Andrey
    et al.
    Univ Bayreuth, Germany.
    Aslandukova, Alena
    Univ Bayreuth, Germany.
    Laniel, Dominique
    Univ Bayreuth, Germany.
    Koemets, Iuliia
    Univ Bayreuth, Germany.
    Fedotenko, Timofey
    Univ Bayreuth, Germany.
    Yuan, Liang
    Univ Bayreuth, Germany.
    Steinle-Neumann, Gerd
    Univ Bayreuth, Germany.
    Glazyrin, Konstantin
    Deutsch Elekt Synchrotron, Germany.
    Hanfland, Michael
    European Synchrotron Radiat Facil, France.
    Dubrovinsky, Leonid
    Univ Bayreuth, Germany.
    Doubrovinckaia, Natalia
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering. Univ Bayreuth, Germany.
    High-Pressure Yttrium Nitride, Y5N14, Featuring Three Distinct Types of Nitrogen Dimers2021In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 125, no 32, p. 18077-18084Article in journal (Refereed)
    Abstract [en]

    Yttrium nitride, Y5N14, was synthesized by direct reaction between yttrium and nitrogen at similar to 50 GPa and similar to 2000 K in a laser-heated diamond anvil cell. High-pressure single-crystal X-ray diffraction revealed that the crystal structure of Y5N14 (space group P4/mbm) contains three distinct types of nitrogen dimers. Crystal chemical analysis and ab initio calculations demonstrated that the dimers [N-2](x-) are crystallographically and chemically nonequivalent and possess distinct noninteger formal charges (x) that make Y5N14 unique among known compounds. Theoretical computations showed that Y5N14 has an anion-driven metallicity, with the filled part of its conduction band formed by nitrogen p-states. The compressibility of Y5N14, determined on decompression down to similar to 10 GPa, was found to be uncommonly high for dinitrides containing +3 cations (the bulk modulus K-0 = 137(6) GPa).

  • 2.
    Bakulin, Artem A.
    et al.
    FOM Institute AMOLF, Netherlands; University of Cambridge, England.
    Xia, Yuxin
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Bakker, Huib J.
    FOM Institute AMOLF, Netherlands.
    Inganäs, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Morphology, Temperature, and Field Dependence Separation in High-Efficiency Solar Cells Based on Polyquinoxaline Copolymer2016In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 120, no 8, p. 4219-4226Article in journal (Refereed)
    Abstract [en]

    Charge separation and recombination are key processes determining the performance of organic optoelectronic devices. Here we combine photoluminescence and photovoltaic characterization of organic solar cell devices with ultrafast multipulse photocurrent spectroscopy to investigate charge generation mechanisms in the organic photovoltaic devices based on a blend of an alternating polyquinoxaline copolymer with fullerene. The combined use of these techniques enables the determination of the contributions of geminate and bimolecular processes to the solar cell performance. We observe that charge separation is not a temperature-activated process in the studied materials. At the same time, the generation of free charges shows a dear external field and morphology dependence. This indicates that the critical step of charge separation involves the nonequilibrium state that is formed at early times after photoexcitation, when the polaronic localization is not yet complete. This work reveals new aspects of molecular level charge dynamics in the organic light-conversion systems.

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  • 3.
    Batista dos Santos, Renato
    et al.
    Institute Federal Baiano, Brazil.
    de Brito Mota, Fernando
    University of Federal Bahia, Brazil.
    Rivelino, Roberto
    University of Federal Bahia, Brazil.
    Gueorguiev, Gueorgui Kostov
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Electric-Field Control of Spin-Polarization and Semiconductor-to-Metal Transition in Carbon-Atom-Chain Devices2017In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 121, no 46, p. 26125-26132Article in journal (Refereed)
    Abstract [en]

    We propose hybrid molecular systems containing small carbon atomic chains interconnected by graphene-like flakes, theoretically predicted as true energy minima, as low-dimensional structures that may be useful in electronic devices at the limit of the atomic miniaturization. The effects of an external electric field applied along the direction of the carbon chains indicate that it is possible to control energy gap and spin polarization with sufficiently high strength, within the limit of the structural restoring of the systems. In this sense, by applying electric fields with magnitudes in the 1-5 V/nm range, we obtain semiconductor-to-metallic transitions for all odd-numbered carbon-chain systems proposed here. Furthermore, high-spin-to-low-spin transitions are determined for these systems as a function of the electric-field magnitude. In the case of the even-numbered carbon-chain systems, the overall electric field effect is pushing electron density near the Fermi level, leading to a gapless or metallic regime at 3.0 V/nm. An electric-field control of the spin-polarization of these latter systems is only achieved by doping the extremities of the graphene-like terminations with sulfur atoms. This finding, however, is beneficial for applications of these systems in spin controlled carbon-based devices connected by gold electrodes, even in the presence of a weak spin-orbit coupling.

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  • 4.
    Benshalom, Nimrod
    et al.
    Weizmann Inst Sci, Israel.
    Asher, Maor
    Weizmann Inst Sci, Israel.
    Jouclas, Remy
    Univ Libre Bruxelles ULB, Belgium.
    Korobko, Roman
    Weizmann Inst Sci, Israel.
    Schweicher, Guillaume
    Univ Libre Bruxelles ULB, Belgium.
    Liu, Jie
    Univ Libre Bruxelles ULB, Belgium.
    Geerts, Yves
    Univ Libre Bruxelles ULB, Belgium; Int Solvay Inst Phys & Chem, Belgium.
    Hellman, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering. Weizmann Inst Sci, Israel.
    Yaffe, Omer
    Weizmann Inst Sci, Israel.
    Phonon-Phonon Interactions in the Polarization Dependence of Raman Scattering2023In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 127, no 36, p. 18099-18106Article in journal (Refereed)
    Abstract [en]

    We have found that the polarization dependence of Raman scattering in organic crystals at finite temperatures can only be described by a fourth-rank tensor formalism. This generalization of the second-rank Raman tensor stems from the effect of off diagonal components in the crystal self-energy on the light scattering mechanism. We thus establish a novel manifestation of phonon-phonon interaction in inelastic light scattering, markedly separate from the better-known phonon lifetime.

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  • 5.
    Berggren, Elin
    et al.
    Uppsala Univ, Sweden.
    Weng, Yi-Chen
    Uppsala Univ, Sweden.
    Li, Qifan
    Linköping University, Department of Science and Technology, Laboratory of Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Yang, Chiyuan
    Linköping University, Department of Science and Technology, Laboratory of Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Johansson, Fredrik O. L.
    KTH Royal Inst Technol, Sweden; Sorbonne Univ, France.
    Cappel, Ute B.
    KTH Royal Inst Technol, Sweden.
    Berggren, Magnus
    Linköping University, Department of Science and Technology, Laboratory of Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Fabiano, Simone
    Linköping University, Department of Science and Technology, Laboratory of Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Lindblad, Andreas
    Uppsala Univ, Sweden.
    Charge Transfer in the P(g<sub>4</sub>2T-T):BBL Organic Polymer Heterojunction Measured with Core-Hole Clock Spectroscopy2023In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 127, no 49, p. 23733-23742Article in journal (Refereed)
    Abstract [en]

    The conductivity of organic polymer heterojunction devices relies on the electron dynamics occurring along interfaces between the acceptor and donor moieties. To investigate these dynamics with chemical specificity, spectroscopic techniques are employed to obtain localized snapshots of the electron behavior at selected interfaces. In this study, charge transfer in blends (by weight 10, 50, 90, and 100%) of p-type polymer P(g(4)2T-T) (bithiophene-thiophene) and n-type polymer BBL (poly(benzimidazo-benzo-phenanthroline)) was measured by resonant Auger spectroscopy. Electron spectra emanating from the decay of core-excited states created upon X-ray absorption in the donor polymer P(g(4)2T-T) were measured in the sulfur KL2,3L2,3 Auger kinetic energy region as a function of the excitation energy. By tuning the photon energy across the sulfur K-absorption edge, it is possible to differentiate between decay paths in which the core-excited electron remained on the atom with the core-hole and those where it tunneled away. Analyzing the competing decay modes of these localized and delocalized (charge-transfer) processes facilitated the computation of charge-transfer times as a function of excitation energy using the core-hole clock method. The electron delocalization times derived from the measurements were found to be in the as/fs regime for all polymer blends, with the fastest charge transfer occurring in the sample with an equal amount of donor and acceptor polymer. These findings highlight the significance of core-hole clock spectroscopy as a chemically specific tool for examining the local charge tunneling propensity, which is fundamental to understanding macroscopic conductivity. Additionally, the X-ray absorption spectra near the sulfur K-edge in the P(g(4)2T-T) polymer for different polymer blends were analyzed to compare molecular structure, orientation, and ordering in the polymer heterojunctions. The 50% donor sample exhibited the most pronounced angular dependence of absorption, indicating a higher level of ordering compared to the other weight blends. Our studies on the electron dynamics of this type of all-polymer donor-acceptor systems, in which spontaneous ground-state electron transfer occurs, provide us with critical insights to further advance the next generation of organic conductors with mixed electron-hole conduction characteristics suitable for highly stable electrodes of relevance for electronic, electrochemical, and optoelectronic applications.

  • 6.
    Birke, Ronald L.
    et al.
    CUNY City Coll, NY 10031 USA; CUNY, NY 10016 USA.
    Lombardi, John R.
    CUNY City Coll, NY 10031 USA; CUNY, NY 10016 USA.
    Saidi, Wissam A.
    University of Pittsburgh, PA USA.
    Norman, Patrick
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Chemistry. Linköping University, Faculty of Science & Engineering.
    Surface-Enhanced Raman Scattering Due to Charge-Transfer Resonances: A Time-Dependent Density Functional Theory Study of Ag-13-4-Mercaptopyridine2016In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 120, no 37, p. 20721-20735Article in journal (Refereed)
    Abstract [en]

    We have used time-dependent density functional theory in conjunction with the CAM-B3LYP functional and MWB28/aug-cc-pVDZ basis set to determine non-, near-, and on-resonance Raman spectra for a complex formed by 4-mercaptopyridine (4-Mpy) binding with a Ag-13 cluster via the thiolate Ag-S bond. Geometry optimizations of the Ag-13-4-mpy complex showed an on-top structure directly bound to one Ag atom with the ring of the molecule almost flat with respect to two Ag atoms of the complex. The corresponding B3LYP/MWB28/aug-cc-pVDZ geometry is also an on-top structure directly bound to one Ag atom, but the molecule is directed away from the surface,. The near-resonance Raman calculations were carried out in the infinite lifetime approximation, while the on-resonant Raman excitation profiles were calculated with the complex polarization propagator (CPP) approach, introducing a half width at half-maximum spectral broadening of 0.2 eV. Calculation of the UV-vis spectra of the isolated 4-Mpy and of the Ag-13-4-Mpy complex showed that binding shifts the spectra from deep in the UV to the visible region. Calculation of the near-resonance Raman spectra of the two structures of the complex at 410 (3.025 eV) and 425 nm (2.918 eV) showed a strong enhancement. A very large variation across vibrational modes by a factor of at least 10(3) was found for both the static chemical enhancement and charge-transfer (CT) enhancement mechanisms. ThiS large variation in enhancement factor indicates that B-term Herzberg-Teller scattering is occurring because inactive or very low intensity modes in the static spectra of the molecule are much stronger in both the static and near-resonance spectra of the Complex. From the excitation profile using the CPP method, an overall surface enhancement on the order 10(3) or higher was found for individual modes on excitation into a CT excited state.

  • 7.
    Bittrich, Eva
    et al.
    Leibniz Inst Polymerforsch Dresden eV, Germany.
    Domke, Jari
    Friedrich Schiller Univ Jena, Germany.
    Jehnichen, Dieter
    Leibniz Inst Polymerforsch Dresden eV, Germany.
    Bittrich, Lars
    Leibniz Inst Polymerforsch Dresden eV, Germany.
    Malanin, Mikhail
    Leibniz Inst Polymerforsch Dresden eV, Germany.
    Janke, Andreas
    Leibniz Inst Polymerforsch Dresden eV, Germany.
    Uhlmann, Petra
    Leibniz Inst Polymerforsch Dresden eV, Germany; Univ Nebraska, NE 68588 USA.
    Eichhorn, Klaus-Jochen
    Leibniz Inst Polymerforsch Dresden eV, Germany.
    Papamichail, Alexis
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Stanishev, Vallery
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Darakchieva, Vanya
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Al-Hussein, Mahmoud
    Univ Jordan, Jordan.
    Levichkova, Marieta
    Heliatek GmbH, Germany.
    Fritz, Torsten
    Friedrich Schiller Univ Jena, Germany.
    Walzer, Karsten
    Heliatek GmbH, Germany.
    Morphology of Thin Films of Aromatic Ellagic Acid and Its Hydrogen Bonding Interactions2020In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 124, no 30, p. 16381-16390Article in journal (Refereed)
    Abstract [en]

    Ellagic acid (EA), an antioxidant from fruits or other plants, has recently evoked interest in the field of organic electronics because of its weak electron donor properties. In this work, the preparation of uniaxial pi-stacked EA films by thermal evaporation on different surfaces is reported for the first time. The (102) lattice plane of the pi-electron system was confirmed as the contact plane for one monolayer equivalent on Ag(111) by low-electron energy diffraction. X-ray and atomic force microscopy measurements revealed nanocrystalline grains with an average inplane size of 50 nm and considerably smaller average out-of-plane crystallite sizes (16-25 nm) in films of 16-75 nm thickness. The influence of different substrates was minor compared to the effect of the film thickness. An increase in the in-plane density of grains at larger film thicknesses was deduced from the trend in their uniaxial optical properties. Weak and strong intermolecular H-bonding interactions were identified in the EA crystal lattice, while a surplus of weak H-bonding was observed for the nanocrystallites in thin films, as compared to bulk EA. Finally, EA was coevaporated with the semiconducting thiophene molecule DCV4T-Et-2 to demonstrate principle interactions with a guest molecule by H-bonding analysis. Our results illustrate the feasibility of applying EA films as alignment layers for templating other semiconducting organic films used in organic electronic devices.

  • 8.
    Björk, Jonas
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Chemistry. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Thermodynamics of an Electrocyclic Ring-Closure Reaction on Au(111)2016In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 120, no 38, p. 21716-21721Article in journal (Refereed)
    Abstract [en]

    We have computationally studied the effects of temperature on the reaction pathway of an electrocyclic ring-closure reaction on the Au(111) surface, particularly focusing on thermodynamic aspects of the reaction. The electrocyclic ring closure is accompanied by a series of dehydrogenation steps, and while it is found that temperature, in terms of vibrational entropy and enthalpy, has a reducing effect on most energy barriers, it does not alter the qualitative appreciation of the reaction kinetics. However, it is found that the way the abstracted hydrogen atoms are treated is crucial for the thermodynamics of the reaction. The overall reaction is highly endothermic but becomes thermodynamically favorable due to the entropy gain of the hydrogen byproducts, which desorb associatively from the surface as H2. The study provides new outlooks for the theoretical treatment of reactions related to on-surface synthesis, anticipated to be instructive for future studies.

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  • 9.
    Björk, Jonas
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics. Linköping University, The Institute of Technology.
    Zhang, Yi-Qi
    Technische Universität München, Garching, Germany.
    Klappenberger, Florian
    Technische Universität München, Garching, Germany.
    Barth, Johannes V.
    Technische Universität München, Garching, Germany.
    Stafström, Sven
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics. Linköping University, The Institute of Technology.
    Unraveling the Mechanism of the Covalent Coupling Between Terminal Alkynes on a Noble Metal2014In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 118, no 6, p. 3181-3187Article in journal (Refereed)
    Abstract [en]

    The mechanism of the newly reported route for surface-assisted covalent coupling of terminal alkynes on Ag(111) is unraveled by density functional theory based transition state calculations. We illustrate that the reaction path is fundamentally different from the classical coupling schemes in wet chemistry. It is initiated by the covalent coupling between two molecules instead of single-molecule dehydrogenation. The silver substrate is found to play an important role stabilizing the intermediate species by chemical bonds, although it is hardly active electronically in the actual coupling step. The dimer intermediate is concluded to undergo two subsequent dehydrogenation processes expected to be rate-limiting according to the comparatively large barriers, which origin is discussed.

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  • 10.
    Bounechada, Djamela
    et al.
    Chalmers, Dept Chem & Biol Engn, SE-41296 Gothenburg, Sweden Chalmers, Competence Ctr Catalysis, SE-41296 Gothenburg, Sweden .
    Darmastuti, Zhafira
    Linköping University, Department of Physics, Chemistry and Biology, Applied Sensor Science. Linköping University, The Institute of Technology.
    Andersson, Mike
    Linköping University, Department of Physics, Chemistry and Biology, Applied Sensor Science. Linköping University, The Institute of Technology.
    Ojamäe, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, The Institute of Technology.
    Lloyd Spetz, Anita
    Linköping University, Department of Physics, Chemistry and Biology, Applied Sensor Science. Linköping University, The Institute of Technology.
    Skoglundh, Magnus
    Chalmers, Dept Chem & Biol Engn, SE-41296 Gothenburg, Sweden Chalmers, Competence Ctr Catalysis, SE-41296 Gothenburg, Sweden.
    Carlsson, Per-Anders
    Chalmers, Dept Chem & Biol Engn, SE-41296 Gothenburg, Sweden Chalmers, Competence Ctr Catalysis, SE-41296 Gothenburg, Sweden.
    Vibrational Study of SOx Adsorption on Pt/SiO22014In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 118, no 51, p. 29713-29723Article in journal (Refereed)
    Abstract [en]

    The formation of ad-SOx species on Pt/SiO2 upon exposure to SO2 in concentrations ranging from 10 to 50 ppm at between 200 and 400 degrees C has been studied by in situ diffuse reflectance infrared Fourier transformed spectroscopy. In parallel, first-principles calculations have been carried out to consolidate the experimental interpretations. It was found that sulfate species form on the silica surface with a concomitant removal/rearrangement of silanol groups. Formation of ad-SOx species occurs only after SO2 oxidation to SO3 on the platinum surface. Thus, SO2 oxidation to SO3 is the first step in the SOx adsorption process, followed by spillover of SO3 to the oxide, and finally, the formation of sulfate species on the hydroxyl positions on the oxide. The sulfate formation is influenced by both temperature and SO2 concentration. Furthermore, exposure to hydrogen is shown to be sufficiently efficient as to remove ad-SOx species from the silica surface.

  • 11.
    Brena, B.
    et al.
    Department of Physics, Uppsala University, Box 518, SE-751 20 Uppsala, Sweden.
    Ojamäe, Lars
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry .
    Surface effects and quantum confinement in nanosized GaN clusters: Theoretical predictions2008In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 112, no 35, p. 13516-13523Article in journal (Refereed)
    Abstract [en]

    The structure and the electronic properties of stoichiometric (GaN) n clusters (with 6 = n = 48) were investigated by means of quantum-chemical hybrid density functional theory (DFT) using the B3LYP functional. Particular emphasis was put on the investigation of the evolution of the physical properties of the clusters as a function of their size. Two types of model clusters were studied. Cage-type structures were found to be the most stable for smaller cluster sizes, whereas for larger sizes conformations cut out from the GaN wurtzite crystal were favorable. The study of the electronic structure shows that the energy gap of the clusters tends to become larger as the dimensions of the clusters increase. The vertical electronic absorption energies were calculated by means of time-dependent (TD) DFT. For such small clusters, probably due to the predominant amount of surface atoms, well-defined quantum confinement effects, as commonly observed in crystalline quantum dots, are not apparent. © 2008 American Chemical Society.

  • 12.
    Bronner, Christopher
    et al.
    Heidelberg Univ, Phys Chem Inst, D-69120 Heidelberg, Germany ; Free Univ Berlin, Fachbereich Phys, D-14195 Berlin, Germany.
    Björk, Jonas
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Chemistry. Linköping University, The Institute of Technology.
    Tegeder, Petra
    Heidelberg Univ, Phys Chem Inst, D-69120 Heidelberg, Germany ; Free Univ Berlin, Fachbereich Phys, D-14195 Berlin, Germany.
    Tracking and removing Br during the on-surface synthesis of a graphene nanoribbon2015In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 119, no 1, p. 486-493Article in journal (Refereed)
    Abstract [en]

    The fabrication of graphene nanoribbons (GNRs) requires a high degree of precision due to the sensitivity of the electronic structure on the edge shape. Using Br-substituted molecular precursors, this atomic precision can be achieved in a thermally induced two-step reaction following Br dissociation on a Au(111) surface. Using DFT, we find evidence that the Br atoms are bound to the intermediate polyanthrylene chains. We employ temperature-programmed desorption to demonstrate the associative desorption of HBr and molecular hydrogen during the final cyclodehydrogenation step of the reaction. Both processes are found to have similar activation barriers. Furthermore, we are able to remove Br atoms from the polyanthrylene chains by providing molecular hydrogen. The subsequent formation of GNR via a cyclodehydrogenation demonstrates that Br does not influence this part of the overall reaction.

  • 13.
    Chen, Peng
    et al.
    Nanyang Technology University.
    Yin, Zongyou
    Nanyang Technology University.
    Huang, Xiao
    Nanyang Technology University.
    Wu, Shixin
    Nanyang Technology University.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Zhang, Hua
    Nanyang Technology University.
    Assembly of Graphene Oxide and Au(0.7)Ag(0.3) Alloy Nanoparticles on SiO(2): A New Raman Substrate with Ultrahigh Signal-to-Background Ratio2011In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 115, no 49, p. 24080-24084Article in journal (Refereed)
    Abstract [en]

    Resonance Raman spectroscopy (RRS) often suffers from the large fluorescence background which obscures the much weaker Raman scattering. To address this fundamental problem, a novel Raman substrate has been fabricated by adsorption of Au(0.7)Ag(0.3) alloy nanoparticles (NPs) on a graphene oxide (GO) coated SiO(2) surface, which offers both excellent Raman enhancement and fluorescence quenching. Our experimental data reveal that a Raman to fluorescence background intensity ratio of 1.6 can be obtained for a highly fluorescent dye like Alexa fluor 488. Moreover, we demonstrate that the Raman enhancement mainly originates from the Au(0.7)Ag(0.3) alloy NPs and that the fluorescence quenching mainly arises from the underlying functionalized GO (FGO) substrate.

  • 14.
    Chen, Shula
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Effects of Strong Band-Tail States on Exciton Recombination Dynamics in Dilute Nitride GaP/GaNP Core/Shell Nanowires2018In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 122, no 33, p. 19212-19218Article in journal (Refereed)
    Abstract [en]

    Exciton dynamics in dilute nitride GaP/GaNP core/shell nanowires (NWs) with pronounced band-tail states formed by nitrogen clusters is investigated using time-resolved photoluminescence (PL) spectroscopy. The emission of excitons localized at the N-related states in the GaNP shell is found to exhibit a stretched exponential decay, with the 1/e lifetime dramatically shortened with decreasing excitation wavelength and reduced shell thickness. The observed PL transient behavior is explained by markedly different exciton lifetimes between the surface and bulk regions of the GaNP shell, that is, similar to 20 ps versus similar to 10 ns, respectively. Despite being trapped at the deep localized N states, the photoexcited excitons are concluded to suffer from pronounced surface recombination via tunneling to the surface states within a distance of 10 nm from the surface, which results in the depth-dependent PL dynamics. The surface recombination rate is, however, lower than that previously reported for GaP, indicative of partial passivation of the surface states by nitrogen. From temperature-dependent PL measurements, characteristic thermal activation energies for the surface and bulk-related nonradiative recombination channels are deduced. The obtained results provide insight into the exciton/carrier dynamics in NW systems with strong localization or alloy disorder, which is important for future nanophotonic and photovoltaic applications of such structures.

  • 15.
    Chen, Yongzhen
    et al.
    Linköping University, Department of Science and Technology, Laboratory of Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Ghosh, Sarbani
    Linköping University, Department of Science and Technology, Laboratory of Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Liu, Xianjie
    Linköping University, Department of Science and Technology, Laboratory of Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Zozoulenko, Igor
    Linköping University, Department of Science and Technology, Laboratory of Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Fahlman, Mats
    Linköping University, Department of Science and Technology, Laboratory of Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Braun, Slawomir
    Linköping University, Department of Science and Technology, Laboratory of Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Experimental and Theoretical Investigation into the Polaron Structure of K-Doped Polyfluorene Films2021In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 125, no 1, p. 937-945Article in journal (Refereed)
    Abstract [en]

    The evolution of the electronic structure and optical transition upon n-doping of poly(9,9-dioctylfluorene) (PFO) films is elucidated with photoelectron spectroscopy, optical absorption, density functional theory (DFT), and time-dependent DFT (TD-DFT) calculations. Optical absorption measurements extending into near infrared show two low-energy absorption features at low doping ratios and an additional peak at a higher energy of similar to 2.2 eV that disappears with increasing doping ratios. A gap state (i.e., polaronic state) close to the Fermi level and a significantly destabilized highest valence band appear in the experimentally measured ultraviolet photoelectron spectra. These experimental results are interpreted by the TD-DFT calculations, which show that the lower energy peaks originate from the excitation from polaronic states to the conduction band, while the higher energy peak mainly originates from the destabilized valence band to conduction band transitions and only appears at low doping ratios (c(red) &lt;= 50%, 0.5 potassium atom per fluorene monomer). The DFT calculations further indicate that polaron pairs rather than bipolarons are preferentially formed at high doping ratios. Comparing the results of doped glassy and beta-phase films, we find that the ordered segments in the beta-phase film disappear due to the dopant (potassium) insertion, resulting in a similar polaronic structure.

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  • 16.
    Chirgwandi, Z G
    et al.
    Chalmers.
    Panas, I
    Chalmers.
    Johansson, L-G
    Chalmers.
    Norden, B
    Chalmers.
    Willander, Magnus
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Winkler, D
    Royal Institute of Technology.
    Properties of a Biophotovoltaic Nanodevice2008In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 112, no 48, p. 18717-18721Article in journal (Refereed)
    Abstract [en]

    Properties of an on-chip photovoltaic nanodevice are demonstrated. The dyes comprise green florescent proteins (GFP). Dependence of recently reported zero external potential bias (ZEPB) photocurrent (I) on temperature, power, and wavelength (lambda) is shown. Correlation between UV-vis spectrum of the GFP and the ZEPB I(lambda) of the device is reported. The temperature dependence suggests the ZEPB photocurrent to reflect a liquid crystal type ordering where the current declines monotonically with increasing temperature. The influence of an external bias on the photocurrent is demonstrated. The resulting light-induced current is analyzed in terms of resistive and quantum mechanical contributions.

  • 17.
    Christodoulou, C.
    et al.
    Humboldt University, Germany .
    Giannakopoulos, A.
    University of Mons, Belgium .
    Nardi, M.V.
    Humboldt University, Germany .
    Ligorio, G.
    Humboldt University, Germany .
    Oehzelt, M.
    Humboldt University, Germany Helmholtz Zentrum Berlin Mat and Energie GmbH, Germany .
    Chen, L.
    University of Mons, Belgium .
    Pasquali, L.
    University of Modena and Reggio Emilia, Italy IOM CNR, Italy University of Johannesburg, South Africa .
    Timpel, M.
    Humboldt University, Germany .
    Giglia, A.
    IOM CNR, Italy .
    Nannarone, S.
    University of Modena and Reggio Emilia, Italy IOM CNR, Italy .
    Norman, Patrick
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics. Linköping University, The Institute of Technology.
    Linares, Mathieu
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics. Linköping University, The Institute of Technology.
    Parvez, K.
    Max Planck Institute Polymer Research, Germany .
    Muellen, K.
    Max Planck Institute Polymer Research, Germany .
    Beljonne, D.
    University of Mons, Belgium .
    Koch, N.
    Humboldt University, Germany Helmholtz Zentrum Berlin Mat and Energie GmbH, Germany .
    Tuning the Work Function of Graphene-on-Quartz with a High Weight Molecular Acceptor2014In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 118, no 9, p. 4784-4790Article in journal (Refereed)
    Abstract [en]

    Ultraviolet and X-ray photoelectron spectroscopies in combination with density functional theory (DFT) calculations were used to study the change in the work function (Phi) of graphene, supported by quartz, as induced by adsorption of hexaazatriphenylene-hexacarbonitrile (HATCN). Near edge X-ray absorption fine structure spectroscopy (NEXAFS) and DFT modeling show that a molecular-density-dependent reorientation of HATCN from a planar to a vertically inclined adsorption geometry occurs upon increasing surface coverage. This, in conjunction with the orientation-dependent magnitude of the interface dipole, allows one to explain the evolution of graphene (Phi) from 4.5 eV up to 5.7 eV, rendering the molecularly modified graphene-on-quartz a highly suitable hole injection electrode.

  • 18.
    Cirera, B.
    et al.
    IMDEA Nanosci, Spain.
    Björk, Jonas
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Otero, R.
    IMDEA Nanosci, Spain; University of Autonoma Madrid, Spain.
    Gallego, J. M.
    CSIC, Spain.
    Miranda, R.
    IMDEA Nanosci, Spain; University of Autonoma Madrid, Spain.
    Ecija, D.
    IMDEA Nanosci, Spain.
    Efficient Lanthanide Catalyzed Debromination and Oligomeric Length-Controlled Ullmann Coupling of Aryl Halides2017In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 121, no 14, p. 8033-8041Article in journal (Refereed)
    Abstract [en]

    Lanthanide elements play a vital role in a broad range of high-tech applications, and there is an increasing interest in their catalytic activity, particularly in organo-metallics. However, their catalytic role on surfaces remains unexplored. Here, we present a scanning tunneling microscopy and density functional theory study of the debromination, contacting, and coupling of dibromine terphenyl species with Dy (f-block element) and Ag (d-block element) adatoms, respectively. We show that Dy debrominates the targeted species more efficiently than Ag adatoms at room temperature, promoting the formation of unprecedented C-Dy-C organo-metallic supramolecules versus C-Ag-C parallel chains for the Ag case. DFT calculations corroborate our results showing an almost spontaneous debromination process with Dy compared to Ag. Upon annealing, for samples containing Dy, the formation of C-Ag-C organometallic bonds and concomitant C-C coupling is inhibited, giving rise to a self-assembly of debrominated monomers, showing only a minority number of covalent dimes species. For samples without Dy covalent chains of irregular length are promoted. Our studies open new avenues for using lanthanide elements as efficient dehalogenation catalysts. Furthermore, we illustrate their potential as inhibitors of uncontrolled C-C coupling reactions, of great relevance for fine-tuning the length of polymeric compounds.

  • 19.
    da Cunha, Wiliam Ferreira
    et al.
    University of Brasilia, Brazil.
    Ribeiro, Luiz Antonio
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics. Linköping University, The Institute of Technology.
    de Almeida Fonseca, Antonio Luciano
    University of Brasilia, Brazil.
    Gargano, Ricardo
    University of Brasilia, Brazil.
    Magela e Silva, Geraldo
    University of Brasilia, Brazil.
    Reactive Scattering between Excitons and Charge Carriers in Conjugated Polymers2014In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 118, no 41, p. 23451-23458Article in journal (Refereed)
    Abstract [en]

    The temperature influence on the scattering process between an exciton and a positively charged carrier (polaron or bipolaron) is theoretically investigated using a version of the SuSchriefferHeeger (SSH) model modified to include temperature, Coulomb interactions, and an external electric field. In general, it is observed that the products of the reactive scattering are spin independent when thermal effects are taken into account. For the interaction between a polaron and an exciton, the polaron can be annihilated, when subjected to temperatures higher than a critical value, or pass through the exciton maintaining both their consistencies, if a lower temperature regime is considered. Regarding the recombination between a bipolaron and an exciton, it is observed that the bipolaron can be annihilated whereas the exciton dissociates into two trions or into one polaron and one trion. In all cases, the recombination mechanisms depend on a suitable balance between temperature and electric field. These results may extend the knowledge about electroluminescence process in conjugated polymers, thus being of potential use to improve internal quantum efficiency in polymer light-emitting diodes.

  • 20.
    Danielsson, Örjan
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Karlsson, Matts
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, Faculty of Science & Engineering.
    Sukkaew, Pitsiri
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Pedersen, Henrik
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Ojamäe, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    A Systematic Method for Predictive In Silico Chemical Vapor Deposition2020In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 124, no 14, p. 7725-7736Article in journal (Refereed)
    Abstract [en]

    A comprehensive systematic method for chemical vapor deposition modeling consisting of seven well-defined steps is presented. The method is general in the sense that it is not adapted to a certain type of chemistry or reactor configuration. The method is demonstrated using silicon carbide (SiC) as a model system, with accurate matching to measured data without tuning of the model. We investigate the cause of several experimental observations for which previous research reports only have had speculative explanations. In contrast to previous assumptions, we can show that SiCl2 does not contribute to SiC deposition. We can confirm the presence of larger molecules at both low and high C/Si ratios, which have been thought to cause so-called step-bunching. We can also show that high concentrations of Si lead to other Si molecules other than the ones contributing to growth, which also explains why the C/Si ratio needs to be lower at these conditions to maintain high material quality as well as the observed saturation in deposition rates. Due to its independence of a chemical system and reactor configuration, the method paves the way for a general predictive CVD modeling tool.

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  • 21.
    Dannetun, Per
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
    Lögdlund, Michael
    Université de Mons-Hainaut, Belgium.
    Spangler, C. W.
    Northen Illinois University, USA.
    Bredas, J. L.
    Université de Mons-Hainaut, Belgium.
    Salaneck, William R.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering. william.r.salaneck@liu.se.
    Evolution of Charge-Induced Gap States in Short Diphenylpolyenes as Studied by Photoelectron Spectroscopy1994In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, The Journal of Physical Chemistry, Vol. 98, no 11, p. 2853-2858Article in journal (Refereed)
    Abstract [en]

    The evolution of doping-induced electronic states within the otherwise forbidden energy gap has been studied as a function of the polyene length in a series of diphenylpolyenes. The chemical and electronic structures ha ve been studied using both X-ray and ultraviolet photoelectron spectroscopies. The results are interpreted with the help of quantum chemical calculations, performed using the semiempirical Austin Model 1 and valence effective Hamiltonian methods. The molecules studied area series of diphenylpolyenes, DPx, with x = 1-7 C=C double bonds in the pol yene part of the molecule. Since the frontier or bitals of the diphenylpolyenes are localized on the polyene chain portion of the molecule, there is a high degree of separation of the phenyl and polyene parts of the 11"-systems. Hence, many chemical and electronic properties of diphenylpolyenes are expected to be similar to those of short-chain trans-polyacetylene. For the longer molecules, n = 6 or 7, the present results indicate the presence of doubly charged, interacting soliton-antisoliton pairs, which appear as two new energy levels in the otherwise forbidden energy gap. In diphenyldecaheptaene to stilbene, i.e. 1 ≤ x ≤ 5, however, a singly charged state is formed at intermediate doping levels, after which the soliton-antisoliton pairs appear for the fully doubly charged systems. These results show that, remarkably, even for very short polyene  segments, charges transferred are stored in the form of ( confined) solitons.

  • 22.
    de Jong, Michel P
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Osikowicz, Wojciech
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Sorensen, S.L.
    Department of Synchrotron Radiation Research, Lund University, Box 118, 221 00 Lund, Sweden.
    Sergeyev, S.
    Laboratory of Polymer Chemistry, Université Libre de Bruxelles, Boulevard du Triomphe, 1050 Bruxelles, Belgium.
    Geerts, Y.H.
    Laboratory of Polymer Chemistry, Université Libre de Bruxelles, Boulevard du Triomphe, 1050 Bruxelles, Belgium.
    Salaneck, William R
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Femtosecond charge transfer in assemblies of discotic liquid crystals2008In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 112, no 40, p. 15784-15790Article in journal (Refereed)
    Abstract [en]

    The electronic coupling strength within columns of discotic liquid crystals is investigated using core-level resonant photoemission spectroscopy. Coexisting well-ordered and disordered regions are identified in thin films of tetra-alkoxy-substituted phthalocyanines with the aid of near edge X-ray absorption fine structure and photoelectron spectroscopies. These different regions are used to derive a lower limit for the intermolecular charge transfer bandwidth within the framework of the core-hole clock principle. We find average charge transfer times on the order of a few femtoseconds, that is, significantly faster than the C(ls) core-hole lifetime, which indicates a surprisingly strong electronic coupling between the phthalocyanine units as compared to what is expected from the charge transport characteristics of this material. © 2008 American Chemical Society.

  • 23.
    Doherty, Walter J
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Friedlein, Rainer
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Salaneck, William R
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Layer-by-layer deposition of copper phthalocyanine from aqueous solution: Molecular orientation, ordering parameters, and electronic structure2007In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 111, no 6, p. 2724-2729Article in journal (Refereed)
    Abstract [en]

    Highly ordered, multilayer films composed of alternating, oppositely charged, polyionic copper phthalocyanines were prepared on HOPG [0001] substrates via layer-by-layer deposition from aqueous solution and characterized by scanning force microscopy and photoelectron spectroscopies. In films of up to four layers, individual layers alternate. Angle-resolved ultraviolet photoelectron spectra are consistent with a molecular orientation parallel to the substrate surface and indicate that structural order is reduced with film thickness © 2007 American Chemical Society.

  • 24.
    Ekström, Ulf
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics . Linköping University, The Institute of Technology.
    Ottosson, Henrik
    Department of Biochemistry and Organic Chemistry, Uppsala university, Sweden.
    Norman, Patrick
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics . Linköping University, The Institute of Technology.
    Characterization of the chemisorption of methylsilane on a Au(1,1,1) surface from the silicon K- and L-edge spectra: a theoretical study using the four-component static exchange approximation2005In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 111, p. 13846-13850Article in journal (Refereed)
    Abstract [en]

    X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure spectra (NEXAFS) of methylsilane, isolated and chemisorbed to a Au(1,1,1) surface, are determined in the fully relativistic four-component static exchange approximation¯both the K- and the L-edge of silicon are addressed in this investigation. In the fully chemisorbed structure, three H(Si) atoms have been cleaved off when Si binds in the hollow site of Au forming three Si−Au bonds of normal length. As due to the tri-coordinated chemisorption, the onsets of the K- and L-edge NEXAFS absorption bands occur some 2.0 and 2.5 eV lower in energy, respectively. The spin−orbit splittings in the silicon 2p-shell are not significantly changed due to adsorption. A partly chemisorbed methylsilane with only one H(Si) bond cleaved was also studied, and it is shown that the polarization dependence in the surface spectra contains details that can be used experimentally to identify the surface coordination of silicon. The red-shifts in the XPS silicon 1s (2p) spectra upon surface binding are 0.95 (0.65) and 1.15 (0.83) eV for the mono- and tricoordinated system, respectively.

  • 25.
    Filippov, Stanislav
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering. Stockholm Univ, Sweden.
    Grinderslev, Jakob B.
    Aarhus Univ, Denmark.
    Andersson, Mikael S.
    Chalmers Univ Technol, Sweden.
    Armstrong, Jeff
    Rutherford Appleton Lab, England.
    Karlsson, Maths
    Chalmers Univ Technol, Sweden.
    Jensen, Torben R.
    Aarhus Univ, Denmark.
    Klarbring, Johan
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Simak, Sergey
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Haussermann, Ulrich
    Stockholm Univ, Sweden.
    Analysis of Dihydrogen Bonding in Ammonium Borohydride2019In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 123, no 47, p. 28631-28639Article in journal (Refereed)
    Abstract [en]

    The structural and vibrational properties of ammonium borohydride, NH4BH4, have been examined by first-principles density functional theory (DFT) calculations and inelastic neutron scattering (INS). The H disordered crystal structure of NH4BH4 is composed of the tetrahedral complex ions NH4+ and BH4-, which are arranged as in the fcc NaCl structure and linked by intermolecular dihydrogen bonding. Upon cooling, the INS spectra revealed a structural transition between 45 and 40 K. The reversible transition occurs upon heating between 46 and 49 K. In the low-temperature form reorientational dynamics are frozen. The libration modes for BH4- and NH4+ are near 300 and 200 cm(-1), respectively. Upon entering the fcc high-temperature form, NH4+ ions attain fast reorientational dynamics, as indicated in the disappearance of the NH4+ libration band, whereas BH4- ions become significantly mobile only at temperatures above 100 K. The vibrational behavior of BH4- ions in NH4BH4 compares well to the heavier alkali metal borohydrides, NaBH4-CsBH4. DFT calculations revealed a nondirectional nature of the dihydrogen bonding in NH4BH4 with only weak tendency for long-range order. Different rotational configurations of complex ions appear quasi-degenerate, which is reminiscent of glasses.

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  • 26.
    Freitas, R. R. Q.
    et al.
    University of Federal Bahia, Brazil.
    Rivelino, R.
    University of Federal Bahia, Brazil.
    Mota, F. de B.
    University of Federal Bahia, Brazil.
    Gueorguiev, Gueorgui Kostov
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    de Castilho, C. M. C.
    University of Federal Bahia, Brazil; University of Federal Bahia, Brazil.
    Energy Barrier Reduction for the Double Proton-Transfer Reaction in Guanine-Cytosine DNA Base Pair on a Gold Surface2015In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 119, no 27, p. 15735-15741Article in journal (Refereed)
    Abstract [en]

    We investigate, by means of first-principles calculations, the impact of a gold surface on the proton-transfer of the guanine-cytosine (GC) DNA base pair. Our calculations employ density functional improvements to correct van der Waals interactions and properly treat a weakly bound GC pair at an Au(111) surface. We adopted the simultaneous double proton-transfer (SDPT) mechanism proposed by Lowdin, which may lead to a spontaneous mutation in the structure of DNA from specific tautomerization involving the base pairs. Our calculated differences in the energetics and kinetics of the SDPT in the GC pair, when in contact with an inert gold surface, indicate a reduction of about 31% in the activation energy barrier of the GC/Au(111) tautomeric equilibrium. This finding gives strong evidence that tautomerism of DNA base pairs, binding to a noble surface, may be indeed relevant for the assessment of a possible point mutation, which could be induced by the presence of gold nanoparticles during DNA replication.

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  • 27.
    Freitas, Rafael R. Q.
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering. University of Federal Bahia, Brazil.
    Rivelino, R.
    University of Federal Bahia, Brazil.
    Mota, F. de Brito
    University of Federal Bahia, Brazil.
    Castilho, C. M. C. de
    University of Federal Bahia, Brazil; University of Federal Bahia, Brazil.
    Kakanakova-Georgieva, Anelia
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Gueorguiev, Gueorgui Kostov
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Topological Insulating Phases in Two-Dimensional Bismuth-Containing Single Layers Preserved by Hydrogenation2015In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 119, no 41, p. 23599-23606Article in journal (Refereed)
    Abstract [en]

    Two-dimensional (2D) binary XBi compounds, where X belongs to group III elements (B, Al, Ga, and In), in a buckled honeycomb structure may originate sizable gap Z2 topological insulators (TIs). These are characterized by exhibiting single band inversion at the Γ point as well as nontrivial edge states in their corresponding nanoribbons. By using first-principles calculations, we demonstrate that hydrogenation of XBi single layers leads to distinct and stable crystal structures, which can preserve their topological insulating properties. Moreover, hydrogenation opens a band gap in this new class of 2D Z2 TIs, with distinct intensities, exhibiting an interesting electronic behavior for viable room-temperature applications of these 2D materials. The nature of the global band gap (direct or indirect) and topological insulating properties depend on the X element type and spatial configuration of the sheet, as well as the applied strain. Our results indicate that the geometric configuration can be crucial for preserving totally the topological characteristics of the hydrogenated sheets. We identify sizable band inversions in the band structure for the relaxed hydrogenated GaBi and InBi in their chairlike configurations and for hydrogenated BBi and AlBi under strain. Based on these findings, hydrogenation gives rise to a flexible chemical tunability and can preserve the band topology of the pristine XBi phases.

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  • 28.
    Ghorbani Shiraz, Hamid
    et al.
    Linköping University, Department of Science and Technology, Laboratory of Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Khan, Zia
    Linköping University, Department of Science and Technology, Laboratory of Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Pere, Daniel
    IMRA Europe SAS, France.
    Liu, Xianjie
    Linköping University, Department of Science and Technology, Laboratory of Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Coppel, Yannick
    Univ Toulouse, France.
    Fahlman, Mats
    Linköping University, Department of Science and Technology, Laboratory of Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Vagin, Mikhail
    Linköping University, Department of Science and Technology, Laboratory of Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Chmielowski, Radoslaw
    IMRA Europe SAS, France.
    Kahn, Myrtil L.
    Univ Toulouse, France.
    Berggren, Magnus
    Linköping University, Department of Science and Technology, Laboratory of Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Crispin, Xavier
    Linköping University, Department of Science and Technology, Laboratory of Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Effect of Oxygen Poisoning on the Bidirectional Hydrogen Electrocatalysis in TaS2 Nanosheets2023In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 127, no 12, p. 5825-5832Article in journal (Refereed)
    Abstract [en]

    Sustainable production of hydrogen gas, a green energy carrier of high density, is possible only by electrolysis of water based on the hydrogen evolution reaction (HER). Here, we report the effect of oxygen poisoning on the efficiency of hydrogen production and the consumption by the HER and the hydrogen oxidation reaction (HOR), respectively, on the interface of platinum group metal-free electrocatalyst TaS2 in pristine form and intercalated by the organic Lewis base hexylamine. The state of the surface probed by photoelectron spectroscopy was significantly altered by both Lewis base doping and oxygen poisoning. This alteration dramatically affects the hydrogen production efficiency in the HER, while the back process by the HOR was less sensitive to the changes in the surface states of the electrocatalysts. The oxygenated and intercalated electrocatalyst shows more than 2 x 105 times lower exchange current density of the HER compared to pristine oxygenated materials.

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  • 29.
    Ghorbani Shiraz, Hamid
    et al.
    Linköping University, Department of Science and Technology, Laboratory of Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Ullah Khan, Zia
    Linköping University, Department of Science and Technology, Laboratory of Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Pere, Daniel
    IMRA Europe SAS, France.
    Liu, Xianjie
    Linköping University, Department of Science and Technology, Laboratory of Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Coppel, Yannick
    Univ Toulouse, France.
    Fahlman, Mats
    Linköping University, Department of Science and Technology, Laboratory of Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Berggren, Magnus
    Linköping University, Department of Science and Technology, Laboratory of Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Chmielowski, Radoslaw
    IMRA Europe SAS, France.
    Kahn, Myrtil L.
    Univ Toulouse, France.
    Vagin, Mikhail
    Linköping University, Department of Science and Technology, Laboratory of Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Crispin, Xavier
    Linköping University, Department of Science and Technology, Laboratory of Organic Electronics. Linköping University, Faculty of Science & Engineering.
    3R-TaS2 as an Intercalation-Dependent Electrified Interface for Hydrogen Reduction and Oxidation Reactions2022In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 126, no 40, p. 17056-17065Article in journal (Refereed)
    Abstract [en]

    Hydrogen technology, as a future breakthrough for the energy industry, has been defined as an environmentally friendly, renewable, and high-power energy carrier. The green production of hydrogen, which mainly relies on electrocatalysts, is limited by the high cost and/ or the performance of the catalytic system. Recently, studies have been conducted in search of bifunctional electrocatalysts accelerating both the hydrogen evolution reaction (HER) and the hydrogen oxidation reaction (HOR). Herein, we report the investigation of the high efficiency bifunctional electrocatalyst TaS2 for both the HER and the HOR along with the asymmetric effect of inhibition by organic intercalation. The linear organic agent, to boost the electron donor property and to ease the process of intercalation, provides a higher interlayer gap in the tandem structure of utilized nanosheets. XRD and XPS data reveal an increase in the interlayer distance of 22%. The HER and the HOR were characterized in a Pt group metal-free electrochemical system. The pristine sample shows a low overpotential of -0.016 Vat the onset. The intercalated sample demonstrates a large shift in its performance for the HER. It is revealed that the intercalation is a potential key strategy for tuning the performance of this family of catalysts. The inhibition of the HER by intercalation is considered as the increase in the operational window of a water-based electrolyte on a negative electrode, which is relevant to technologies of electrochemical energy storage.

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  • 30.
    Ghosh, Sarbani
    et al.
    Linköping University, Department of Science and Technology, Laboratory of Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Gueskine, Viktor
    Linköping University, Department of Science and Technology, Laboratory of Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Berggren, Magnus
    Linköping University, Department of Science and Technology, Laboratory of Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Zozoulenko, Igor
    Linköping University, Department of Science and Technology, Laboratory of Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Electronic Structures and Optical Absorption of N-Type Conducting Polymers at Different Doping Levels2019In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 123, no 25, p. 15467-15476Article in journal (Refereed)
    Abstract [en]

    Theoretical understanding of the electronic structure and optical transitions in n-doped conducting polymers is still controversial for polaronic and bipolaronic states and is completely missing for the case of a high doping level. In the present paper, the electronic structure and optical properties of the archetypical n-doped conducting polymer, double-stranded benzimidazo-benzophenanthroline ladder (BBL), are studied using the density functional theory (DFT) and the time dependent DFT method. We find that a polaronic state in the BBL chain is a spin-resolved doublet where the spin degeneracy is lifted. The ground state of two electrons corresponds to a triplet polaron pair, which is in stark contrast to a commonly accepted picture where two electrons are postulated to form a spinless bipolaron. The total spin gradually increases until the reduction level reaches c(red) = 100% (i.e., one electron per monomer unit). With further increase of the reduction level, the total spin decreases until it becomes 0 for the reduction level c(red) = 200%. The calculated results reproduce the experimentally observed spin signal without any phenomenological parameters. A detailed analysis of the evolution of the electronic structure of BBL and its absorption spectra with increase in reduction level is presented. The calculated UV-vis-NIR spectra are compared with the available experimental results. The electronic structure and optical absorption for different reduction levels presented here are generic to a wide class of conducting polymers, which is illustrated by the corresponding calculations for another archetypical conducting polymer, poly(3,4-ethylenedioxythiophene) (best known as PEDOT).

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  • 31.
    Goyenola, Cecilia
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Lai, Chung-Chuan
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Näslund, Lars-Åke
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Lu, Jun
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Högberg, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Rosén, Johanna
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Gueorguiev, Gueorgui Kostov
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Theoretical prediction and synthesis of CSxFy thin films2016In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 120, no 17, p. 9527-9534Article in journal (Refereed)
    Abstract [en]

    A new carbon-based compound: CSxFy was addressed by density functional theory calculations and synthesized by reactive magnetron sputtering. Geometry optimizations and energy calculations were performed on graphene-like model systems containing sulfur and fluorine atoms. It is shown that [S+F] concentrations in the range of 0−10 at.%, structural ordered characteristics similar to graphene pieces containing ring defects are energetically feasible. The modeling predicts that CSxFy thin films with graphite and fullerene-like characteristics may be obtained for the mentioned concentration range. Accordingly, thin films were synthesized from a graphite solid target and sulfur hexafluoride as reactive gas. In agreement with the theoretical prediction, transmission electron microscopy characterization and selected area electron diffraction confirmed the presence of small ordered clusters with graphitic features in a sample containing 0.4 at.% of S and 3.4 at.% of F.

  • 32.
    Goyenola, Cecilia
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Stafström, Sven
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Gueorguiev, Gueorgui Kostov
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Structural Patterns Arising during Synthetic Growth of Fullerene-Like Sulfocarbide2012In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 116, no 39, p. 21124-21131Article in journal (Refereed)
    Abstract [en]

    Carbon-based fullerene-like (FL) solid compounds are a new class of materials with extraordinary mechanical properties, which can be tuned by the dopant choice and its concentration. In this work, FL sulfocarbide (CSx) was studied by DFT simulations during synthetic growth with CmSn (m, n andlt;= 2). The energetic and structural effects of S atoms at C sites in a graphene-like network were addressed by geometry optimizations and cohesive energy calculations. Results showed that for S concentrations lower than 10 at. %, smoothly bent pure hexagonal networks predominate. For higher S concentrations, the higher defect concentration leads to stronger deformation of the graphene-like sheets. It was determined that FL-CSx is well-structured (not amorphous) for S contents between 10 and 20 at. %. In contrast to other FL materials, bond rotation mechanisms are not expected to play any significant role during FL-CSx formation, and cross-linking sites are less frequent and may be assimilated in the planar structure during growth. Both quasi-planar networks and cage-like conformations were found to form during the synthetic growth of CSx. The detailed analysis of how CSx structural patterns form during its synthetic growth provides a realistic picture for the deposition of this novel compound by magnetron sputtering.

  • 33.
    Goyenola, Cecilia
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Stafström, Sven
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics. Linköping University, The Institute of Technology.
    Schmidt, Susann
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Gueorguiev, Gueorgui Kostov
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Carbon Fluoride, CFx: Structural Diversity as Predicted by First Principles2014In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 118, no 12, p. 6514-6521Article in journal (Refereed)
    Abstract [en]

    Fluorinated carbon-based thin films offer a wide range of properties for many technological applications that depend on the microstructure of the films. To gain a better understanding of the role of fluorine in the structural formation of these films, CFx systems based on graphene-like fragments were studied by first-principles calculations. Generally, the F concentration determines the type of film that can be obtained. For low F concentrations (up to similar to 5 at. %), films with fullerene-like as well as graphite-like features are expected. Larger F concentrations (greater than= 10 at. %) give rise to increasingly amorphous carbon films. Further increasing the F concentration in the films leads to formation of a polymer-like microstructure. To aid the characterization of CFx systems generated by computational methods, a statistical approach is developed.

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  • 34.
    Gueskine, Viktor
    et al.
    Linköping University, Department of Science and Technology, Laboratory of Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Singh, Amritpal
    Linköping University, Department of Science and Technology. Linköping University, Faculty of Science & Engineering.
    Vagin, Mikhail
    Linköping University, Department of Science and Technology, Laboratory of Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Crispin, Xavier
    Linköping University, Department of Science and Technology, Laboratory of Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Zozoulenko, Igor
    Linköping University, Department of Science and Technology, Laboratory of Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Molecular Oxygen Activation at a Conducting Polymer: Electrochemical Oxygen Reduction Reaction at PEDOT Revisited, a Theoretical Study2020In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 124, no 24, p. 13263-13272Article in journal (Refereed)
    Abstract [en]

    Molecular oxygen requires activation in order to be reduced, which prompts extensive searching for efficient and sustainable electrode materials to drive electrochemical oxygen reduction reaction (ORR), of primary importance for energy production and storage. A conjugated polymer PEDOT is a metal-free material for which promising ORR experimental results have been obtained. However, sound theoretical understanding of this reaction at an organic electrode is insufficient, as the concepts inherited from electrocatalysis at transition metals are not necessarily relevant for a molecular organic material. In this work, we critically analyze the basics of electrochemical ORR and build a model for our DFT calculations of the reaction thermodynamics based on this analysis. Altogether, this work leads to a conclusion that outer sphere electron transfer that currently attracts increasing attention in the context of ORR is a viable mechanism at a conducting polymer electrode.

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  • 35.
    Gustafsson, Håkan
    et al.
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Ahrén, Maria
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, Faculty of Science & Engineering.
    Söderlind, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Córdoba Gallego, José M.
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology.
    Käll, Per-Olov
    Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry. Linköping University, Faculty of Science & Engineering.
    Nordblad, Per
    Uppsala Universitet.
    Westlund, Per-Olof
    Umeå Universitet.
    Uvdal, Kajsa
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, Faculty of Science & Engineering.
    Engström, Maria
    Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Faculty of Health Sciences.
    Magnetic and Electron Spin Relaxation Properties of (GdxY1-x)2O3 (0 ≤ x ≤ 1) Nanoparticles Synthesized by the Combustion Method. Increased Electron Spin Relaxation Times with Increasing Yttrium Content2011In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 115, no 13, p. 5469-5477Article in journal (Refereed)
    Abstract [en]

    The performance of a magnetic resonance imaging contrast agent (CA) depends on several factors, including the relaxation times of the unpaired electrons in the CA. The electron spin relaxation time may be a key factor for the performance of new CAs, such as nanosized Gd2O3 particles. The aim of this work is, therefore, to study changes in the magnetic susceptibility and the electron spin relaxation time of paramagnetic Gd2O3 nanoparticles diluted with increasing amounts of diamagnetic Y2O3. Nanoparticles of (GdxY1-x)2O3 (0 e x e 1) were prepared by the combustion method and thoroughly characterized (by X-ray di.raction, transmission electron microscopy, thermogravimetry coupled with mass spectroscopy, photoelectron spectroscopy, Fourier transform infrared spectroscopy, and magnetic susceptibility measurements). Changes in the electron spin relaxation time were estimated by observations of the signal line width in electron paramagnetic resonance spectroscopy, and it was found that the line width was dependent on the concentration of yttrium, indicating that diamagnetic Y2O3 may increase the electron spin relaxation time of Gd2O3 nanoparticles.

  • 36.
    Huang, Jing-Jia
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. SGL Carbon GmbH, Germany.
    Militzer, Christian
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering. SGL Carbon GmbH, Germany.
    Wijayawardhana, Charles
    SGL Carbon GmbH, Germany.
    Forsberg, Urban
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Ojamäe, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Pedersen, Henrik
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Controlled CVD Growth of Highly ⟨111⟩-Oriented 3C-SiC2022In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 126, no 23, p. 9918-9925Article in journal (Refereed)
    Abstract [en]

    Highly ⟨111⟩-oriented 3C-SiC coatings with a distinct surface morphology consisting of hexagonally shaped pyramidal crystals were prepared by chemical vapor deposition (CVD) using silicon tetrachloride (SiCl4) and toluene (C7H8) at T ≤ 1250 °C and ptot = 10 kPa. In contrast, similar deposition conditions, with methane (CH4) as the carbon precursor, resulted in randomly oriented 3C-SiC coatings with a cauliflower-like surface of SiC crystallites. No excess carbon was detected in the highly ⟨111⟩-oriented 3C-SiC samples despite the use of aromatic hydrocarbons. The difference in the preferred growth orientation of the 3C-SiC coatings deposited by using C7H8 and CH4 as the carbon precursors was explained via quantum chemical calculations of binding energies on various crystal planes. The adsorption energy of C6H6 on the SiC (111) plane was 6 times higher than that on the (110) plane. On the other hand, CH3 exhibited equally strong adsorption on both planes. This suggested that the highly ⟨111⟩-oriented 3C-SiC growth with C7H8 as the carbon precursor, where both C6H6 and CH3 were considered the main active carbon-containing film forming species, was due to the highly preferred adsorption on the (111) plane, while the lower surface energy of the (110) plane controlled the growth orientation in the CH4 process, in which only CH3 contributed to the film deposition. 

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  • 37.
    Imam, Mewlude
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. European Spallat Source ERIC, Sweden.
    Souqui, Laurent
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Herritsch, Jan
    Philipps University of Marburg, Germany.
    Stegmueller, Andreas
    Philipps University of Marburg, Germany.
    Höglund, Carina
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. European Spallat Source ERIC, Sweden.
    Schmidt, Susann
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Hall-Wilton, Richard
    European Spallat Source ERIC, Sweden; Mid Sweden University, Sweden.
    Högberg, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Tonner, Ralf
    Philipps University of Marburg, Germany.
    Pedersen, Henrik
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Gas Phase Chemistry of Trimethylboron in Thermal Chemical Vapor Deposition2017In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 121, no 47, p. 26465-26471Article in journal (Refereed)
    Abstract [en]

    Alkylboranes, such as trimethylboron (TMB) and triethylboron (TEB), are promising alternative precursors in low temperature chemical vapor deposition (CVD) of boron-containing thin films. In this study, CVD growth of B-C films using TMB and quantum-chemical calculations to elucidate a gas phase chemical mechanism were undertaken. Dense, amorphous, boron-rich (B/C 1.5-3) films were deposited at 1000 degrees C in both dihydrogen and argon ambients, while films with crystalline B4C and B25C inclusions were deposited at 1100 degrees C in dihydrogen. A script-based automatization scheme was implemented for the quantum-chemical computations to enable time efficient screening of thousands of possible gas phase CVD reactions. The quantum-chemical calculations suggest TMB is mainly decomposed by an unimolecular alpha-H elimination of methane, which is complemented by dihydrogen-assisted elimination of methane in dihydrogen.

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  • 38.
    Jansson, Mattias
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Chen, Shula
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    La, Rui
    University of Calif San Diego, CA 92093 USA.
    Stehr, Jan Eric
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Tu, Charles W.
    University of Calif San Diego, CA 92093 USA; University of Calif San Diego, CA 92093 USA.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Effects of Nitrogen Incorporation on Structural and Optical Properties of GaNAsP Nanowires2017In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 121, no 12, p. 7047-7055Article in journal (Refereed)
    Abstract [en]

    In this work, we carry out a comprehensive investigation of structural and optical effects in GaNAsP nanowires (NWs), which are novel materials promising for advanced photovoltaic applications. Despite a significant mismatch in electronegativity between N and As/P atoms, we show that incorporation of nitrogen does not degrade structural quality of the nanowires and the fabricated NW arrays have excellent compositional uniformity among individual wires. From temperature-dependent photoluminescence (PL) measurements, statistical fluctuations of the alloy composition are shown to lead to localization of photoexcited carriers at low temperatures but do not affect material properties at room temperature. According to time-resolved PL measurements, the room-temperature carrier lifetime increases in the GaNAsP NWs as compared with the GaAsP NWs, which indicates reduced nonradiative recombination. Moreover, in spite of the very low N content in the studied NWs (up to 0.16%), their bandgap energy can be tuned by more than 100 meV. This is accompanied by about 30% reduction in the temperature dependence of the bandgap energy. The presented results demonstrate that alloying of GaAsP with nitrogen provides an additional means of design optimization, beneficial for, e.g., NW-based intermediate band solar cells that are highly dependent on the optimum bandgap structure.

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  • 39.
    Jasiunas, Rokas
    et al.
    Ctr Phys Sci & Technol, Lithuania.
    Zhang, Huotian
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Yuan, Jun
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering. Cent South Univ, Peoples R China.
    Zhou, Xuehong
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Qian, Deping
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Zou, Yingping
    Cent South Univ, Peoples R China.
    Devizis, Andrius
    Ctr Phys Sci & Technol, Lithuania.
    Sulskus, Juozas
    Vilnius Univ, Lithuania.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Gulbinas, Vidmantas
    Ctr Phys Sci & Technol, Lithuania; Vilnius Univ, Lithuania.
    From Generation to Extraction: A Time-Resolved Investigation of Photophysical Processes in Non-fullerene Organic Solar Cells2020In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 124, no 39, p. 21283-21292Article in journal (Refereed)
    Abstract [en]

    Non-fullerene organic solar cells (NFOSCs) demonstrate record efficiencies exceeding 16%. In comparison with cells with the fullerene-based acceptor, the NFOSCs benefit from a longer wavelength absorption, which leads to a small highest occupied molecular orbital (HOMO) level offset. Here, we use several advanced transient investigation techniques, covering timescale from sub-ps to mu s, to address all sequence of processes starting from photoexcitation of donors or acceptors to carrier extraction in several NFOSCs and cells with phenyl-C71-butyric acid methyl ester (PCBM). Though small offsets result in higher open-circuit voltage, we show that at the same time, it limits cell performance because of inefficient hole transfer from excited acceptors to donors and enhanced geminate recombination. We demonstrate that 100 meV HOMO level offset and proper acceptor molecule structures are sufficient for efficient hole transfer (&gt;70%) and for reduction of the geminate recombination losses down to about 20%. Subsequent extraction of unbound charge carriers in all NFOSCs is slightly faster than in cells with PCBM, while non-geminate carrier recombination causing additional losses is slightly slower in the best performing NFOSCs than in cells with PCBM.

  • 40.
    Jasiuunas, Rokas
    et al.
    Ctr Phys Sci & Technol, Lithuania.
    Jasinskas, Vidmantas
    Ctr Phys Sci & Technol, Lithuania.
    Zhang, Huotian
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Upreti, Tanvi
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering. Heidelberg Univ, Germany.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Kemerink, Martijn
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering. Heidelberg Univ, Germany.
    Gulbinas, Vidmantas
    Ctr Phys Sci & Technol, Lithuania.
    Carrier Mobility Dynamics under Actual Working Conditions of Organic Solar Cells2021In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 125, no 27, p. 14567-14575Article in journal (Refereed)
    Abstract [en]

    Although organic photovoltaics has made significant progress since its appearance decades ago, the underlying physics of charge transport in working cells is still under debate. Carrier mobility, determining the carrier extraction and recombination, is one of the most important but complex and still poorly understood parameters. Low-energy charge carrier states acting as traps play a particularly important role in carrier transport. Occupation of these states under real operation conditions of solar cells induces additional complexity. In this study, we use several transient methods and numerical modeling to address carrier transport under actual working conditions of bulk heterojunction organic solar cells based on fullerene and nonfullerene acceptors. We show that occupation of low-energy states strongly depends on the blend materials and the effective electric field. We define conditions when such occupation increases carrier mobility, making it less time-dependent on the microsecond time scale, and when its influence is only marginal. We also show that the initial mobility, determined by carrier relaxation within the high-energy part of the distributed density of states, strongly decreases with time independently of the low-energy state population.

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  • 41.
    Kepčija, Nenad
    et al.
    Technische Universität München, Germany.
    Zhang, Yi-Qi
    Technische Universität München, Germany.
    Kleinschrodt, Martin
    Technische Universität München, Germany.
    Björk, Jonas
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics. Linköping University, The Institute of Technology.
    Klyatskaya, Svetlana
    Karlsruhe Institute of Technology, Germany.
    Klappenberger, Florian
    Technische Universität München, Germany.
    Ruben, Mario
    Karlsruhe Institute of Technology, Germany.
    Barth, Johannes V.
    Technische Universität München, Germany.
    Steering On-Surface Self-Assembly of High-Quality Hydrocarbon Networks with Terminal Alkynes2013In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 117, no 8, p. 3987-3995Article in journal (Refereed)
    Abstract [en]

    The two-dimensional (2D) self-assembly of 1,3,5-triethynyl-benzene (TEB) and de novo synthesized 1,3,5-tris-(4-ethynylphenyl)benzene (Ext-TEB) on Ag(111) was investigated by means of scanning tunneling microscopy (STM) under ultrahigh vacuum (UHV) conditions. Both 3-fold symmetric molecules form long-range ordered nanoporous networks featuring organizational chirality, mediated by novel, planar 6-fold cyclic binding motifs. The key interaction for the expression of the motifs is identified as C–H···π bonding. For Ext-TEB, an additional open-porous phase exists with the 3-fold motif. The nature of the underlying noncovalent bonding schemes is thoroughly analyzed by density functional theory (DFT) calculations including van der Waals corrections. The comparison of calculations focusing on isolated 2D molecular sheets and those including the substrate reveals the delicate balance between the attractive molecule–molecule interaction, mediated by both the terminal alkyne and the phenyl groups, and the molecule–substrate interaction responsible for the commensurability and the regularity of the networks. Comparison with bulk structures of similar molecules suggests that these strictly planar cyclic binding motifs appear only in 2D environments.

  • 42.
    Khikhlovskyi, Vsevolod
    et al.
    Eindhoven University of Technology, Netherlands; TNO, Netherlands.
    Wang, Rui
    TNO, Netherlands.
    van Breemen, Albert J. J. M.
    TNO, Netherlands.
    Gelinck, Gerwin H.
    TNO, Netherlands.
    Janssen, Rene A. J.
    Eindhoven University of Technology, Netherlands.
    Kemerink, Martijn
    Department of Applied Physics, Eindhoven University of Technology, Eindhoven, The Netherlands.
    Nanoscale Organic Ferroelectric Resistive Switches2014In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 118, no 6, p. 3305-3312Article in journal (Refereed)
    Abstract [en]

    Organic ferroelectric resistive switches function by grace of nanoscale phase separation in a blend of a semiconducting and a ferroelectric polymer that is sandwiched between metallic electrodes. In this work, various scanning probe techniques are combined with numerical modeling to unravel their operational mechanism. Resistive switching is shown to result from modulation of the charge injection barrier at the semiconductor-electrode interfaces. The modulation is driven by the stray field of the polarization charges in the ferroelectric phase and consequently is restricted to regions where semiconductor and ferroelectric phases exist in close vicinity. Since each semiconductor domain can individually be switched and read out, a novel, nanoscale memory element is demonstrated. An ultimate information density of similar to 30 Mb/cm(2) is estimated for this bottom-up defined memory device.

  • 43.
    Lawton, T J
    et al.
    Tufts University, MA 02155 USA .
    Pushkarev, V
    Carnegie Mellon University, PA 15213 USA .
    Broitman, Esteban
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Reinicker, A
    Carnegie Mellon University, PA 15213 USA .
    Sykes, E C H
    Tufts University, MA 02155 USA .
    Gellman, A J
    US DOE, PA 15236 USA Carnegie Mellon University, PA 15213 USA .
    Initial Oxidation of Cu(hkl) Surfaces Vicinal to Cu(111): A High-Throughput Study of Structure Sensitivity2012In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 116, no 30, p. 16054-16062Article in journal (Refereed)
    Abstract [en]

    The initial stage in the oxidation of Cu single crystal surfaces has been studied on a surface structure spread single crystal ((SC)-C-4) exposing a continuous distribution of all Cu(hkl) surface orientations lying within 10 degrees polar angle of the (111) plane, Cu(111)+/- 10 degrees-(SC)-C-4. The uptake of oxygen across the Cu(111) +/- 10 degrees-(SC)-C-4 during exposure to O-2 at 300 K has been measured using spatially resolved X-ray photoelectron spectroscopy (XPS), and the resulting Cu2O surface oxide layer has been imaged using scanning tunneling microscopy (STM). Uptake of oxygen is dependent on surface step density and increases with increasing polar angle relative to the (111) pole. In contrast, the oxygen uptake does not depend on the crystallographic orientation of the step edge or, in other words, the kink density along the step edge. STM images reveal that once oxidation of the step edges begins, all of the boundaries of the Cu2O step oxide layer are oriented along (100) step edges in the Cu(111) terrace independent of the initial orientation of the step. In other words, the oxidizing step edges have no memory of their original orientation, and thus, the step growth depends only on step density and not on the kink density along the step edge. The combined use of both spatially resolved XPS and atomic scale imaging with STM on a Cu(111) +/- 10 degrees-(SC)-C-4 has provided unique insight into the origins of structure-sensitive surface chemistry.

  • 44.
    Lenz, Annika
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry. Linköping University, The Institute of Technology.
    Selegård, Linnea
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, Faculty of Science & Engineering.
    Söderlind, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Inorganic Chemistry. Linköping University, Faculty of Science & Engineering.
    Larsson, Arvid
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Uvdal, Kajsa
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, Faculty of Science & Engineering.
    Ojamäe, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry. Linköping University, The Institute of Technology.
    Käll, Per-Olov
    Linköping University, Department of Physics, Chemistry and Biology, Inorganic Chemistry. Linköping University, The Institute of Technology.
    ZnO Nanoparticles Functionalized with Organic Acids: An Experimental and Quantum-Chemical Study2009In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 113, no 40, p. 17332-17341Article in journal (Refereed)
    Abstract [en]

    Electrochemical synthesis and physical characterization of ZnO nanoparticles functionalized with four different organic acids, three aromatic (benzoic, nicotinic, and trans-cinnamic acid) and one nonaromatic (formic acid), are reported. The functionalized nanoparticles have been characterized by X-ray powder diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, UV−vis, and photoluminescence spectroscopy. The adsorption of the organic acids at ZnO nanoparticles was further analyzed and interpreted using quantum-chemical density-functional theory computations. Successful functionalization of the nanoparticles was confirmed experimentally by the measured splitting of the carboxylic group stretching vibrations as well as by the N(1s) and C(1s) peaks from XPS. From a comparison between computed and experimental IR spectra, a bridging mode adsorption geometry was inferred. PL spectra exhibited a remarkably stronger near band edge emission for nanoparticles functionalized with formic acid as compared to the larger aromatic acids. From the quantum-chemical computations, this was interpreted to be due to the absence of aromatic adsorbate or surface states in the band gap of ZnO, caused by the formation of a complete monolayer of HCOOH. In the UV−vis spectra, strong charge-transfer transitions were observed.

  • 45.
    Li, Fenghong
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Zhan, Yiqiang
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Lee, Tsung-Hsun
    Institute of Innovation and Advanced Studies, National Cheng Kung University, Tainan, Taiwan.
    Liu, Xianjie
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Chikamatsu, Akira
    Department of Chemistry, The University of Tokyo, Tokyo, Japan.
    Guo, Tzung-Fang
    Institute of Electro-Optical Science and Engineering, Advanced Optoelectronic Technology Center, National Cheng Kung University, Tainan, Taiwan.
    Lin, Hong-Ji
    National Synchrotron Radiation Research Center, Hsin-Chu, Taiwan.
    Huang, J C A
    Institute of Innovation and Advanced Studies, National Cheng Kung University, Tainan, Taiwan.
    Fahlman, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Modified Surface Electronic and Magnetic Properties of La(0.6)Sr(0.4)MnO(3) Thin Films for Spintronics Applications2011In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 115, no 34, p. 16947-16953Article in journal (Refereed)
    Abstract [en]

    We present the surface electronic and magnetic properties of half-metal La(0.6)Sr(0.4)MnO(3) (LSMO) thin film modified by a simple cleaning procedure, the so-called SC1 (5 H(2)O, 1 NH(4)OH, I H(2)O(2)), at 85 degrees C for 10-40 min in ambient atmosphere. In this study, photoemission spectroscopy (XPS/UPS), X-ray absorption spectroscopy (XAS), and X-ray magnetic circular dichroism (XMCD) are used to characterize these properties of the manganites. Thanks to SC1 treatment, the work function of LSMO changes from 4.0-4.1 to 4.8-4.9 eV obtained from UPS measurements, while its surface roughness changes from 0.268 to 0.796 nm in AFM images. Combined 0 1s, Mn 2p, Sr 3d, La 4d, and Mn 3s core-level XPS spectroscopy investigations suggest that Mn and Sr contents decrease at the surface and the Mn value becomes 3.7 due to SC1 treament. Mn L-edge XAS spectra of LSMO thin film demonstrate that SC1 treatment results in a removal of Mn(2+) and an increase of the Mn(4+) concentration. OK-edge XAS spectra further prove an enhancement of hybridization between O 2p orbitals and e(g)down arrow, of Mn 3d induced by more Mn(4+). XMCD results show that SC1 treatment does not induce any drastic changes of magnetic properties of the LSMO thin film surface.

  • 46.
    Liang, Xia
    et al.
    Imperial Coll London, England.
    Klarbring, Johan
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering. Imperial Coll London, England.
    Baldwin, William J.
    Univ Cambridge, England.
    Li, Zhenzhu
    Imperial Coll London, England.
    Csanyi, Gabor
    Univ Cambridge, England.
    Walsh, Aron
    Imperial Coll London, England; Ewha Womans Univ, South Korea.
    Structural Dynamics Descriptors for Metal Halide Perovskites2023In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 127, no 38, p. 19141-19151Article in journal (Refereed)
    Abstract [en]

    Metal halide perovskites have shown extraordinary performance in solar energy conversion technologies. They have been classified as "soft semiconductors" due to their flexible corner-sharing octahedral networks and polymorphous nature. Understanding the local and average structures continues to be challenging for both modeling and experiments. Here, we report the quantitative analysis of structural dynamics in time and space from molecular dynamics simulations of perovskite crystals. The compact descriptors provided cover a wide variety of structural properties, including octahedral tilting and distortion, local lattice parameters, molecular orientations, as well as their spatial correlation. To validate our methods, we have trained a machine learning force field (MLFF) for methylammonium lead bromide (CH3NH3PbBr3) using an on-the-fly training approach with Gaussian process regression. The known stable phases are reproduced, and we find an additional symmetry-breaking effect in the cubic and tetragonal phases close to the phase-transition temperature. To test the implementation for large trajectories, we also apply it to 69,120 atom simulations for CsPbI3 based on an MLFF developed using the atomic cluster expansion formalism. The structural dynamics descriptors and Python toolkit are general to perovskites and readily transferable to more complex compositions.

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  • 47.
    Lima, E.R.A.
    et al.
    Escola de Química, Universidade Federal do Rio de Janeiro, Cidade Universitária, CEP 21949-900, Rio de Janeiro, RJ, Brazil, Programa de Engenharia Química, COPPE, Universidade Federal do Rio de Janeiro, 21945-970, Rio de Janeiro, RJ, Brazil.
    Biscaia, Jr. E.C.
    Biscaia Jr., E.C., Programa de Engenharia Química, COPPE, Universidade Federal do Rio de Janeiro, 21945-970, Rio de Janeiro, RJ, Brazil.
    Boström, Mathias
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics .
    Tavares, F.W.
    Escola de Química, Universidade Federal do Rio de Janeiro, Cidade Universitária, CEP 21949-900, Rio de Janeiro, RJ, Brazil.
    Prausnitz, J.M.
    Department of Chemical Engineering, University of California, Berkeley, CA 94720-1462, Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720.
    Osmotic second virial coefficients and phase diagrams for aqueous proteins from a much-improved poisson - Boltzmann equation2007In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 111, no 43, p. 16055-16059Article in journal (Refereed)
    Abstract [en]

    A much-improved Poisson - Boltzmann equation for two globular proteins using bispherical coordinates is used to establish the potential of mean force (PMF) between two globular lysozyme particles. Calculations presented here include previously ignored ion-protein nonelectrostatic potentials. The lysozyme - lysozyme PMF is used to calculate osmotic second virial coeffiencients. The theoretical PMF curve as a function of sodium chloride concentration is successfully compared with that from experiment. Our theoretical PMF shows how the second virial coefficient and the phase diagram depends on salt concentration, pH and, most notably, on the choice of salt in the aquous solution. © 2007 American Chemical Society.

  • 48.
    Lischka, Matthias
    et al.
    Tech Univ Munich, Germany; Deutsch Museum, Germany.
    Fritton, Massimo
    Tech Univ Munich, Germany; Deutsch Museum, Germany.
    Eichhorn, Johanna
    Tech Univ Munich, Germany; Deutsch Museum, Germany.
    Vyas, Vijay S.
    Max Planck Inst Solid State Res, Germany; Marquette Univ, WI 53233 USA.
    Strunskus, Thomas
    Christian Albrechts Univ Kiel, Germany.
    Lotsch, Bettina V.
    Max Planck Inst Solid State Res, Germany; Nanosyst Initiat Munich, Germany; Ctr NanoSci, Germany; Univ Munich LMU, Germany.
    Björk, Jonas
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Heckl, Wolfgang M.
    Tech Univ Munich, Germany; Deutsch Museum, Germany; Nanosyst Initiat Munich, Germany; Ctr NanoSci, Germany.
    Lackinger, Markus
    Tech Univ Munich, Germany; Deutsch Museum, Germany; Nanosyst Initiat Munich, Germany; Ctr NanoSci, Germany.
    On-Surface Polymerization of 1,6-Dibromo-3,8-diiodpyrene-A Comparative Study on Au(111) Versus Ag(111) by STM, XPS, and NEXAFS2018In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 122, no 11, p. 5967-5977Article in journal (Refereed)
    Abstract [en]

    The surface chemistry of 1,6-dibromo-3,8-diiodopyrene (Br2I2Py) is comparatively studied on Au(111) versus Ag(111) surfaces under ultrahigh vacuum conditions by a combination of high-resolution scanning tunneling microscopy (STM) and X-ray spectroscopy. The chemical state of the molecular networks, that is, the dehalogenation and the possible formation of organometallic intermediates, is assessed by X-ray photoelectron spectroscopy. In addition, pyrene tilt angles are quantified by carbon K-edge near edge X-ray absorption fine structure experiments. Upon room-temperature (RT) deposition of Br2I2Py onto Au(111), only partial deiodination was found, and STM revealed the coexistence of ordered arrangements of both intact Br2I2Py molecules and organometallic dimers as well as few larger aggregates. Further annealing to 100 C triggered full deiodination followed by the formation of organometallic chains of otherwise still brominated molecules. By contrast, on Ag(111), iodine is fully and bromine is partly dissociated upon RT deposition of Br2I2Py. The initially disordered organometallic aggregates can be reorganized into more ordered structures by mild annealing at 125 degrees C. Yet, the conversion of the organometallic intermediates into well-defined cross-linked quasi 2D covalent networks was neither possible on Au(111) nor on Ag(111). This is attributed to the large steric hindrance in the covalently linked adsorbed state.

  • 49.
    Liu, Xianjie
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Grueneis, Alexander
    University of Vienna, Austria .
    Haberer, Danny
    Leibniz IFW Dresden, Germany .
    Fedorov, Alexander V.
    Leibniz IFW Dresden, Germany .
    Vilkov, Oleg
    St Petersburg State University, Russia .
    Strupinski, Wlodek
    Institute Elect Mat Technology, Poland .
    Pichler, Thomas
    University of Vienna, Austria .
    Tunable Interface Properties between Pentacene and Graphene on the SIC Substrate2013In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 117, no 8, p. 3969-3975Article in journal (Refereed)
    Abstract [en]

    Understanding energy-level alignment and molecular growth characteristics of an organic semiconductor on the graphene surface is crucial for graphene-related device performance. Here we demonstrate that tunable interface properties and molecular orientation can be achieved by modifying graphene films on a SiC substrate with monolayer copper-hexadecafluorophthalocyanine (F16CuPc) molecules. On clean graphene, pentacene molecules form a tilted configuration even at very low coverage (one or two monolayers) rather than flat-lying as on the graphite surface. Pentacene molecules prefer to grow with a (022) plane parallel to the clean graphene surface. With increasing coverage, X-ray adsorption data indicate there is no obvious change of molecular stacking orientation. The corresponding hole injection barrier is about 0.7 eV. On the modified graphene where thin (one or two monolayers) F16CuPc molecules are flat-lying on graphene, an almost perfect up-standing molecular stacking of pentacene film was formed on the modified surface. A low hole injection barrier of 0.3 eV was observed. Furthermore, the interface of dirty graphene upon pentacene was also discussed.

  • 50.
    Liu, Yanfeng
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Zhang, Jianyun
    Chinese Acad Sci, Peoples R China; Univ Chinese Acad Sci, Peoples R China.
    Zhou, Guanqing
    Shanghai Jiao Tong Univ, Peoples R China.
    Liu, Feng
    Shanghai Jiao Tong Univ, Peoples R China.
    Zhu, Xiaozhang
    Chinese Acad Sci, Peoples R China; Univ Chinese Acad Sci, Peoples R China.
    Zhang, Fengling
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Electric Field Facilitating Hole Transfer in Non-Fullerene Organic Solar Cells with a Negative HOMO Offset2020In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 124, no 28, p. 15132-15139Article in journal (Refereed)
    Abstract [en]

    The record high photoinduced current and power conversion efficiencies of organic solar cells (OSCs) should be attributed to the significant contribution of non-fullerene electron acceptors via hole transfer to electron donors and/or a pronounced decrease in energy losses for exciton dissociation by aligned highest occupied molecular orbitals (HOMOs) or lowest unoccupied molecular orbitals (LUMOs). However, the hole transfer mechanism in those highly efficient non-fullerene OSCs with small HOMO offsets has not been extensively studied and fully understood, yet. Herein, we comparatively study the hole transfer kinetics in two OSCs with a positive (0.05 eV) and a negative (-0.07 eV) HOMO offset (Delta HOMO) based on polymer donor PTQ10 paired with non-fullerene acceptors ZITI-C or ZITI-N. Short-circuit current densities (J(sc)) of 20.42 and 12.81 mA cm(-2) are achieved in the OSCs based on PTQ10:ZITI-C (Delta HOMO = 0.05 eV) and PTQ10:ZITI-N (Delta HOMO = -0.07 eV) with an optimized donor (D):acceptor (A) ratio of 1:1, respectively, despite the small and even negative Delta HOMO. Results from time-resolved transient absorption spectroscopy show slower hole transfer (14.3 ps) in PTQ10:ZITI-N than that (3.7 ps) in PTQ10:ZITI-C. To understand the decent J(sc) value in the OSCs of PTQ10:ZITI-N, the temperature and electric field dependences of hole transfer are investigated in low-donor-content OSCs (D:A ratio of 1:9) in which photocurrent is dominated by the contribution via hole transfer from ZITI-N to PTQ10. Devices based on PTQ10:ZITI-C and PTQ10:ZITI-N show similar free charge generation behavior as a function of temperature, whereas the external quantum efficiencies of the PTQ10:ZITI-N device exhibit a much stronger bias dependence than that of PTQ10:ZITI-C, which suggests that the electric field facilitates exciton dissociation in PTQ10:ZITI-N where the energetic driving force alone cannot efficiently dissociate excitons.

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