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  • 1.
    Bakulin, Artem A.
    et al.
    FOM Institute AMOLF, Netherlands; University of Cambridge, England.
    Xia, Yuxin
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
    Bakker, Huib J.
    FOM Institute AMOLF, Netherlands.
    Inganäs, Olle
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
    Gao, Feng
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
    Morphology, Temperature, and Field Dependence Separation in High-Efficiency Solar Cells Based on Polyquinoxaline Copolymer2016Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 120, nr 8, s. 4219-4226Artikel i tidskrift (Refereegranskat)
    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.

  • 2.
    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
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Electric-Field Control of Spin-Polarization and Semiconductor-to-Metal Transition in Carbon-Atom-Chain Devices2017Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 121, nr 46, s. 26125-26132Artikel i tidskrift (Refereegranskat)
    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.

  • 3.
    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
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk kemi. Linköpings universitet, Tekniska fakulteten.
    Surface-Enhanced Raman Scattering Due to Charge-Transfer Resonances: A Time-Dependent Density Functional Theory Study of Ag-13-4-Mercaptopyridine2016Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 120, nr 37, s. 20721-20735Artikel i tidskrift (Refereegranskat)
    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.

  • 4.
    Björk, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk kemi. Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska fakulteten. Linköping University.
    Thermodynamics of an Electrocyclic Ring-Closure Reaction on Au(111)2016Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 120, nr 38, s. 21716-21721Artikel i tidskrift (Refereegranskat)
    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.

  • 5.
    Björk, Jonas
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Beräkningsfysik. Linköpings universitet, Tekniska högskolan.
    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
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Beräkningsfysik. Linköpings universitet, Tekniska högskolan.
    Unraveling the Mechanism of the Covalent Coupling Between Terminal Alkynes on a Noble Metal2014Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 118, nr 6, s. 3181-3187Artikel i tidskrift (Refereegranskat)
    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.

  • 6.
    Bounechada, Djamela
    et al.
    Chalmers, Dept Chem & Biol Engn, SE-41296 Gothenburg, Sweden Chalmers, Competence Ctr Catalysis, SE-41296 Gothenburg, Sweden .
    Darmastuti, Zhafira
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad sensorvetenskap. Linköpings universitet, Tekniska högskolan.
    Andersson, Mike
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad sensorvetenskap. Linköpings universitet, Tekniska högskolan.
    Ojamäe, Lars
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Kemi. Linköpings universitet, Tekniska högskolan.
    Lloyd Spetz, Anita
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad sensorvetenskap. Linköpings universitet, Tekniska högskolan.
    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/SiO22014Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 118, nr 51, s. 29713-29723Artikel i tidskrift (Refereegranskat)
    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.

  • 7.
    Brena, B.
    et al.
    Department of Physics, Uppsala University, Box 518, SE-751 20 Uppsala, Sweden.
    Ojamäe, Lars
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Fysikalisk Kemi.
    Surface effects and quantum confinement in nanosized GaN clusters: Theoretical predictions2008Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 112, nr 35, s. 13516-13523Artikel i tidskrift (Refereegranskat)
    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.

  • 8.
    Bronner, Christopher
    et al.
    Heidelberg Univ, Phys Chem Inst, D-69120 Heidelberg, Germany ; Free Univ Berlin, Fachbereich Phys, D-14195 Berlin, Germany.
    Björk, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk kemi. Linköpings universitet, Tekniska högskolan.
    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 nanoribbon2015Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 119, nr 1, s. 486-493Artikel i tidskrift (Refereegranskat)
    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.

  • 9.
    Chen, Peng
    et al.
    Nanyang Technology University.
    Yin, Zongyou
    Nanyang Technology University.
    Huang, Xiao
    Nanyang Technology University.
    Wu, Shixin
    Nanyang Technology University.
    Liedberg, Bo
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Sensorvetenskap och Molekylfysik. Linköpings universitet, Tekniska högskolan.
    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 Ratio2011Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 115, nr 49, s. 24080-24084Artikel i tidskrift (Refereegranskat)
    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.

  • 10.
    Chen, Shula
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Ytors Fysik och Kemi. Linköpings universitet, Tekniska fakulteten.
    Chen, Weimin
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Ytors Fysik och Kemi. Linköpings universitet, Tekniska fakulteten.
    Buyanova, Irina
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Ytors Fysik och Kemi. Linköpings universitet, Tekniska fakulteten.
    Effects of Strong Band-Tail States on Exciton Recombination Dynamics in Dilute Nitride GaP/GaNP Core/Shell Nanowires2018Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 122, nr 33, s. 19212-19218Artikel i tidskrift (Refereegranskat)
    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.

  • 11.
    Chirgwandi, Z G
    et al.
    Chalmers.
    Panas, I
    Chalmers.
    Johansson, L-G
    Chalmers.
    Norden, B
    Chalmers.
    Willander, Magnus
    Linköpings universitet, Institutionen för teknik och naturvetenskap. Linköpings universitet, Tekniska högskolan.
    Winkler, D
    Royal Institute of Technology.
    Properties of a Biophotovoltaic Nanodevice2008Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 112, nr 48, s. 18717-18721Artikel i tidskrift (Refereegranskat)
    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.

  • 12.
    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
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Beräkningsfysik. Linköpings universitet, Tekniska högskolan.
    Linares, Mathieu
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Beräkningsfysik. Linköpings universitet, Tekniska högskolan.
    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 Acceptor2014Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 118, nr 9, s. 4784-4790Artikel i tidskrift (Refereegranskat)
    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.

  • 13.
    Cirera, B.
    et al.
    IMDEA Nanosci, Spain.
    Björk, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska fakulteten.
    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 Halides2017Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 121, nr 14, s. 8033-8041Artikel i tidskrift (Refereegranskat)
    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.

  • 14.
    da Cunha, Wiliam Ferreira
    et al.
    University of Brasilia, Brazil.
    Ribeiro, Luiz Antonio
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Beräkningsfysik. Linköpings universitet, Tekniska högskolan.
    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 Polymers2014Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 118, nr 41, s. 23451-23458Artikel i tidskrift (Refereegranskat)
    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.

  • 15.
    Dannetun, Per
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska fakulteten.
    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.
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska fakulteten. william.r.salaneck@liu.se.
    Evolution of Charge-Induced Gap States in Short Diphenylpolyenes as Studied by Photoelectron Spectroscopy1994Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, The Journal of Physical Chemistry, Vol. 98, nr 11, s. 2853-2858Artikel i tidskrift (Refereegranskat)
    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.

  • 16.
    de Jong, Michel P
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Ytors Fysik och Kemi.
    Osikowicz, Wojciech
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Ytors Fysik och Kemi.
    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
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Ytors Fysik och Kemi.
    Femtosecond charge transfer in assemblies of discotic liquid crystals2008Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 112, nr 40, s. 15784-15790Artikel i tidskrift (Refereegranskat)
    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.

  • 17.
    Doherty, Walter J
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Friedlein, Rainer
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Ytors Fysik och Kemi.
    Salaneck, William R
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Ytors Fysik och Kemi.
    Layer-by-layer deposition of copper phthalocyanine from aqueous solution: Molecular orientation, ordering parameters, and electronic structure2007Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 111, nr 6, s. 2724-2729Artikel i tidskrift (Refereegranskat)
    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.

  • 18.
    Ekström, Ulf
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Beräkningsfysik. Linköpings universitet, Tekniska högskolan.
    Ottosson, Henrik
    Department of Biochemistry and Organic Chemistry, Uppsala university, Sweden.
    Norman, Patrick
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Beräkningsfysik. Linköpings universitet, Tekniska högskolan.
    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 approximation2005Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 111, s. 13846-13850Artikel i tidskrift (Refereegranskat)
    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.

  • 19.
    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
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    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 Surface2015Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 119, nr 27, s. 15735-15741Artikel i tidskrift (Refereegranskat)
    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.

  • 20.
    Freitas, Rafael R. Q.
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska fakulteten. 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
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Gueorguiev, Gueorgui Kostov
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Topological Insulating Phases in Two-Dimensional Bismuth-Containing Single Layers Preserved by Hydrogenation2015Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 119, nr 41, s. 23599-23606Artikel i tidskrift (Refereegranskat)
    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.

  • 21.
    Goyenola, Cecilia
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Lai, Chung-Chuan
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Näslund, Lars-Åke
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Lu, Jun
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Högberg, Hans
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Hultman, Lars
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Rosén, Johanna
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Gueorguiev, Gueorgui Kostov
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Theoretical prediction and synthesis of CSxFy thin films2016Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 120, nr 17, s. 9527-9534Artikel i tidskrift (Refereegranskat)
    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.

  • 22.
    Goyenola, Cecilia
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Stafström, Sven
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Beräkningsfysik. Linköpings universitet, Tekniska högskolan.
    Hultman, Lars
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Gueorguiev, Gueorgui Kostov
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Structural Patterns Arising during Synthetic Growth of Fullerene-Like Sulfocarbide2012Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 116, nr 39, s. 21124-21131Artikel i tidskrift (Refereegranskat)
    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.

  • 23.
    Goyenola, Cecilia
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Stafström, Sven
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Beräkningsfysik. Linköpings universitet, Tekniska högskolan.
    Schmidt, Susann
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Hultman, Lars
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Gueorguiev, Gueorgui Kostov
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Carbon Fluoride, CFx: Structural Diversity as Predicted by First Principles2014Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 118, nr 12, s. 6514-6521Artikel i tidskrift (Refereegranskat)
    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.

  • 24.
    Gustafsson, Håkan
    et al.
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV.
    Ahrén, Maria
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Molekylär ytfysik och nanovetenskap. Linköpings universitet, Tekniska fakulteten.
    Söderlind, Fredrik
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Kemi. Linköpings universitet, Tekniska fakulteten.
    Córdoba Gallego, José M.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Nanostrukturerade material. Linköpings universitet, Tekniska högskolan.
    Käll, Per-Olov
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Fysikalisk Kemi. Linköpings universitet, Tekniska fakulteten.
    Nordblad, Per
    Uppsala Universitet.
    Westlund, Per-Olof
    Umeå Universitet.
    Uvdal, Kajsa
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Molekylär ytfysik och nanovetenskap. Linköpings universitet, Tekniska fakulteten.
    Engström, Maria
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiologi. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Hälsouniversitetet.
    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 Content2011Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 115, nr 13, s. 5469-5477Artikel i tidskrift (Refereegranskat)
    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.

  • 25.
    Imam, Mewlude
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten. European Spallat Source ERIC, Sweden.
    Souqui, Laurent
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Herritsch, Jan
    Philipps University of Marburg, Germany.
    Stegmueller, Andreas
    Philipps University of Marburg, Germany.
    Höglund, Carina
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten. European Spallat Source ERIC, Sweden.
    Schmidt, Susann
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Hall-Wilton, Richard
    European Spallat Source ERIC, Sweden; Mid Sweden University, Sweden.
    Högberg, Hans
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Birch, Jens
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Tonner, Ralf
    Philipps University of Marburg, Germany.
    Pedersen, Henrik
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Kemi. Linköpings universitet, Tekniska fakulteten.
    Gas Phase Chemistry of Trimethylboron in Thermal Chemical Vapor Deposition2017Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 121, nr 47, s. 26465-26471Artikel i tidskrift (Refereegranskat)
    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.

  • 26.
    Jansson, Mattias
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Ytors Fysik och Kemi. Linköpings universitet, Tekniska fakulteten. Linköpings universitet, Institutionen för fysik, kemi och biologi, Funktionella elektroniska material.
    Chen, Shula
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Ytors Fysik och Kemi. Linköpings universitet, Tekniska fakulteten. Linköpings universitet, Institutionen för fysik, kemi och biologi, Funktionella elektroniska material.
    La, Rui
    University of Calif San Diego, CA 92093 USA.
    Stehr, Jan Eric
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Ytors Fysik och Kemi. Linköpings universitet, Tekniska fakulteten. Linköpings universitet, Institutionen för fysik, kemi och biologi, Funktionella elektroniska material.
    Tu, Charles W.
    University of Calif San Diego, CA 92093 USA; University of Calif San Diego, CA 92093 USA.
    Chen, Weimin
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Ytors Fysik och Kemi. Linköpings universitet, Tekniska fakulteten. Linköpings universitet, Institutionen för fysik, kemi och biologi, Funktionella elektroniska material.
    Buyanova, Irina
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Ytors Fysik och Kemi. Linköpings universitet, Tekniska fakulteten. Linköpings universitet, Institutionen för fysik, kemi och biologi, Funktionella elektroniska material.
    Effects of Nitrogen Incorporation on Structural and Optical Properties of GaNAsP Nanowires2017Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 121, nr 12, s. 7047-7055Artikel i tidskrift (Refereegranskat)
    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.

  • 27.
    Kepčija, Nenad
    et al.
    Technische Universität München, Germany.
    Zhang, Yi-Qi
    Technische Universität München, Germany.
    Kleinschrodt, Martin
    Technische Universität München, Germany.
    Björk, Jonas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Beräkningsfysik. Linköpings universitet, Tekniska högskolan.
    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 Alkynes2013Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 117, nr 8, s. 3987-3995Artikel i tidskrift (Refereegranskat)
    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.

  • 28.
    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 Switches2014Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 118, nr 6, s. 3305-3312Artikel i tidskrift (Refereegranskat)
    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.

  • 29.
    Lawton, T J
    et al.
    Tufts University, MA 02155 USA .
    Pushkarev, V
    Carnegie Mellon University, PA 15213 USA .
    Broitman, Esteban
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    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 Sensitivity2012Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 116, nr 30, s. 16054-16062Artikel i tidskrift (Refereegranskat)
    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.

  • 30.
    Lenz, Annika
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Fysikalisk Kemi. Linköpings universitet, Tekniska högskolan.
    Selegård, Linnea
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Molekylär ytfysik och nanovetenskap. Linköpings universitet, Tekniska fakulteten.
    Söderlind, Fredrik
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Oorganisk Kemi. Linköpings universitet, Tekniska fakulteten.
    Larsson, Arvid
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Holtz, Per-Olof
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Uvdal, Kajsa
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Molekylär ytfysik och nanovetenskap. Linköpings universitet, Tekniska fakulteten.
    Ojamäe, Lars
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Fysikalisk Kemi. Linköpings universitet, Tekniska högskolan.
    Käll, Per-Olov
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Oorganisk Kemi. Linköpings universitet, Tekniska högskolan.
    ZnO Nanoparticles Functionalized with Organic Acids: An Experimental and Quantum-Chemical Study2009Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 113, nr 40, s. 17332-17341Artikel i tidskrift (Refereegranskat)
    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.

  • 31.
    Li, Fenghong
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Ytors Fysik och Kemi. Linköpings universitet, Tekniska högskolan.
    Zhan, Yiqiang
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Ytors Fysik och Kemi. Linköpings universitet, Tekniska högskolan.
    Lee, Tsung-Hsun
    Institute of Innovation and Advanced Studies, National Cheng Kung University, Tainan, Taiwan.
    Liu, Xianjie
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Ytors Fysik och Kemi. Linköpings universitet, Tekniska högskolan.
    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
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Ytors Fysik och Kemi. Linköpings universitet, Tekniska högskolan.
    Modified Surface Electronic and Magnetic Properties of La(0.6)Sr(0.4)MnO(3) Thin Films for Spintronics Applications2011Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 115, nr 34, s. 16947-16953Artikel i tidskrift (Refereegranskat)
    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.

  • 32.
    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
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik.
    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 equation2007Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 111, nr 43, s. 16055-16059Artikel i tidskrift (Refereegranskat)
    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.

  • 33.
    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
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska fakulteten.
    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 NEXAFS2018Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 122, nr 11, s. 5967-5977Artikel i tidskrift (Refereegranskat)
    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.

  • 34.
    Liu, Xianjie
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Ytors Fysik och Kemi. Linköpings universitet, Tekniska högskolan.
    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 Substrate2013Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 117, nr 8, s. 3969-3975Artikel i tidskrift (Refereegranskat)
    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.

  • 35.
    Liu, Yuan
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Kemi. Linköpings universitet, Tekniska fakulteten.
    Ojamäe, Lars
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Kemi. Linköpings universitet, Tekniska fakulteten.
    C-13 Chemical Shift in Natural Gas Hydrates from First-Principles Solid-State NMR Calculations2016Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 120, nr 2, s. 1130-1136Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Natural gas hydrates (NGHs) are of interest both as a prospective energy resource and for possible technological applications. C-13 NMR technology is a powerful tool to characterize NGHs, and in this work, the trends and origins of C-13 NMR chemical shifts of hydrocarbon molecules in NGHs from quantum-chemical first-principles calculations on solid state phases are presented. The chemical shift is found to decrease as the size of the water cavities increases for single occupancy NGHs, and to increase as the amount of CH4 increases for the multioccupancy cases. In most cases, the chemical shift of NGHs monotonically increases as the external pressure increases. Furthermore, the chemical shift can be mainly attributed to the host-guest interaction together with a small contributions from water molecules for tight environments and mainly depends on host-guest interaction for loose environments. The theoretical results provide useful information for identification of the types of clathrate phases and guest molecules included in NGH samples taken from natural sites.

  • 36.
    Liu, Yuan
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Kemi. Linköpings universitet, Tekniska fakulteten. Not Found:Linkoping Univ, Dept Chem, IFM, SE-58183 Linkoping, Sweden.
    Ojamäe, Lars
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Kemi. Linköpings universitet, Tekniska fakulteten.
    CH-Stretching Vibrational Trends in Natural Gas Hydrates Studied by Quantum-Chemical Computations2015Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 119, nr 30, s. 17084-17091Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Vibrational Raman spectrosopy of hydrocarbon CH-stretching vibrations is often-used to study natural gas, hydrates., In this work, CH-stretching vibrational, Raman spectra of hydrocarbon molectles (CH4, C2H6, C(3)H6, C3H8, C4H8, i-C4H10, and n-C4H10) encapsulated in the water cages (D, ID, T, P, H, and I) of the SI, sII, sH, and sK crystal phases. are derived from quantum-chemical computations at the omega B97X-D/6-311++G(24,2p) level of theory. The trends of CH-stretching vibrational frequencies Of hydrocarbon Molecules in natural gas hydrates are found to follow the prediction by the loose cage tight cage model: as the size of Water cavity increases, the CH frequencies will first decrease and: then increase until equal to-that in the gas phase. In the "tight cage" situation, the frequency will be greater than in the gas phase; in the "loose cage" situation, the frequency will be smaller or asymptotic to that in the gas phase. Furthermore, the OH-stretching frequencies are sensitive to the H-bond configuration, and the varying strengths of H-bonds for different configurations are reflected by,the frequency distribution in the corresponding subspectra.

  • 37.
    Ma, Zaifei
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Tang, Zheng
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Wang, Ergang
    Chalmers, Sweden .
    Andersson, Mats R
    Chalmers, Sweden .
    Inganäs, Olle
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Zhang, Fengling
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Influences of Surface Roughness of ZnO Electron Transport Layer on the Photovoltaic Performance of Organic Inverted Solar Cells2012Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 116, nr 46, s. 24462-24468Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Here, we demonstrate the correlation between the surface roughness of the ZnO interlayer used as an electron transporting interlayer (ETL) in organic inverted solar cells (ISCs) and the photovoltaic performance of the ISCs. Three different surfaces of the ZnO ETL are studied in ISCs with the polymer poly[2,3-bis-(3-octyloxyphenyl)-quinoxaline-5,8-diyl-alt-thiophene-2,5-diyl] (TQ1) mixed with [6,6]-phenyl C71 butyric acid methyl ester (PC71BM) as the active layer. The results obtained from these ISCs show that power conversion efficiency increases from 2.7% to 3.9% when the root-mean-square roughness of the ZnO layer decreases from 48 to 1.9 nm. Moreover, it is found that the short-circuit current density is higher in the ISC based on the smoother ZnO interlayer, with a larger donor/acceptor (D/A) interfacial area in the active layer that facilitates exciton dissociation. The reduced effective interfacial area between the photoactive layer and the ZnO interlayer with decreased ZnO surface roughness leads to an observed improvement in both fill factor and open circuit voltage, which is ascribed to a reduced concentration of traps at the interface between the ZnO interlayer and the active layer.

  • 38.
    Magnuson, Martin
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Eriksson, Fredrik
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Hultman, Lars
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Högberg, Hans
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Bonding Structures of ZrHx Thin Films by X-ray Spectroscopy2017Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 121, s. 25750-25758Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The variation in local atomic structure and chemical bonding of ZrHx (x=0.15, 0.30, 1.16) magnetron sputtered thin films are investigated by Zr K-edge (1s) X-ray absorption near-edge structure and extended X-ray absorption fine structure spectroscopies. A chemical shift of the Zr K-edge towards higher energy with increasing hydrogen content is observed due to charge-transfer and an ionic or polar covalent bonding component between the Zr 4d and the H 1s states with increasing valency for Zr. We find an increase in the Zr-Zr bond distance with increasing hydrogen content from 3.160 Å in the hexagonal closest-packed metal (a-phase) to 3.395 Å in the understoichiometric d-ZrHx film (CaF2-type structure) with x=1.16 that largely resembles that of bulk d-ZrH2. For yet lower hydrogen contents, the structures are mixed a- and d-phases, while sufficient hydrogen loading (x>1) yields a pure δ-phase that is understoichiometric, but thermodynamically stable. The change in the hydrogen content and strain is discussed in relation to the corresponding change of bond lengths, hybridizations, and trends in electrical resistivity.

  • 39.
    Maiwulidan, Yimamu
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten. European Spallat Source ERIC, Sweden.
    Höglund, Carina
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska fakulteten. European Spallat Source ERIC, Sweden.
    Jensen, Jens
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Schmidt, Susann
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten. European Spallat Source ERIC, Sweden.
    Ivanov, Ivan Gueorguiev
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Hall-Wilton, Richard
    European Spallat Source ERIC, Sweden; Mid Sweden University, Sweden.
    Birch, Jens
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Pedersen, Henrik
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Kemi. Linköpings universitet, Tekniska fakulteten.
    Trimethylboron as Single-Source Precursor for Boron-Carbon Thin Film Synthesis by Plasma Chemical Vapor Deposition2016Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 120, nr 38, s. 21990-21997Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Boron–carbon (BxC) thin films are potential neutron converting layers for 10B-based neutron detectors. However, as common material choices for such detectors do not tolerate temperatures above 500 °C, a low temperature deposition route is required. Here, we study trimethylboron B(CH3)3 (TMB) as a single-source precursor for the deposition of BxC thin films by plasma CVD using Ar plasma. The effect of plasma power, TMB/Ar flow ratio and total pressure, on the film composition, morphology, chemical bonding, and microstructures are investigated. Dense and boron-rich films (B/C = 1.9) are achieved at high TMB flow under a low total pressure and high plasma power, which rendered an approximate substrate temperature of ∼300 °C. Films mainly contain B–C bonds with the presence of B–O and C–C, which is attributed to be the origin of formed amorphous carbon in the films. The high H content (15 ± 5 at. %) is almost independent of deposition parameters and contributed to lower the film density (2.16 g/cm3). The plasma compositional analysis shows that the TMB molecule decomposes to mainly atomic H, C2, BH, and CH. A plasma chemical model for the decomposition of TMB with BH and CH as the plausible film depositing species in the plasma is proposed.

  • 40.
    Malysheva, Lyuba
    et al.
    Bogolyubov Institute for Theoretical Physics, 03680, Kiev, Ukraine.
    Onipko, Alexander
    Bogolyubov Institute for Theoretical Physics, 03680, Kiev, Ukraine.
    Fyrner, Timmy
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Kemi. Linköpings universitet, Tekniska fakulteten.
    Lee, Hung-Hsun
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Molekylär fysik. Linköpings universitet, Tekniska fakulteten.
    Valiokas, Ramūnas
    Department of Nanoengineering, Center for Physical Sciences and Engineering, Savanoriu 231, LT-02300 Vilnius, Lithuania.
    Konradsson, Peter
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Organisk Kemi. Linköpings universitet, Tekniska högskolan.
    Liedberg, Bo
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Sensorvetenskap och Molekylfysik. Linköpings universitet, Tekniska högskolan.
    Spectroscopic Characterization and Modeling of Methyl- and Hydrogen-Terminated Oligo (ethylene glycol) Self-Assembled Monolayers2012Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 116, nr 22, s. 12008-12016Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Two series of oligo (ethylene glycol) (OEG) thiol compounds HS-(CH2CH2O)nR with R = CH3, H and n = 5, 6, 7, have been synthesized and used to form self-assembled monolayers (SAMs) on gold. The data from null ellipsometry, infrared reflection-absorption spectroscopy and ab initio calculations of this type of OH- and CH3-terminated OEG SAMs are used to examine the rarely addressed in-SAM orientation of oligo (ethylene glycols) and to provide detailed assignments of infrared bands in the fingerprint and CH-stretching regions. Based on these results, a new spectral band has been observed at 2947 cm-1 and identified by the firstprinciple calculations as localized vibrations that are specific for hydrogen-terminated OEG thiolate SAMs. This band can be used as an indicator of a high crystalline like ordering. It is further more stressed that theory agrees with the experimentally obtained CH-stretching spectra remarkably well if, and only if, the OEG helix axis within studied SAMs is tilted by about 20o with respect to the surface normal.

  • 41.
    Martinsson, Erik
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Molekylär fysik. Linköpings universitet, Tekniska fakulteten.
    Mehdi Shahjamali, Mohammad
    Nanyang Technology University, Singapore .
    Enander, Karin
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Molekylär fysik. Linköpings universitet, Tekniska fakulteten.
    Boey, Freddy
    Nanyang Technology University, Singapore .
    Xue, Can
    Nanyang Technology University, Singapore .
    Aili, Daniel
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Molekylär fysik. Linköpings universitet, Tekniska fakulteten.
    Liedberg, Bo
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Molekylär fysik. Linköpings universitet, Tekniska fakulteten.
    Local Refractive Index Sensing Based on Edge Gold-Coated Silver Nanoprisms2013Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 117, nr 44, s. 23148-23154Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Bulk and surface refractive index sensitivity for localized surface plasmon resonance (LSPR) sensing based on edge gold-coated silver nanoprisms (GSNPs) and gold nanospheres was investigated and compared with conventional surface plasmon resonance (SPR) sensing based on propagating surface plasmons. The hybrid GSNPs benefit from an improved stability since the gold frame protecting the unstable silver facets located at the silver nanoprisms (SNPs) edges and tips prevents truncation or rounding of their sharp tips or edges, maintaining a high refractive index sensitivity even under harsh conditions. By using layer-by-layer deposition of polyelectrolytes and protein adsorption, we found that GSNPs exhibit 4-fold higher local refractive index sensitivity in close proximity (andlt;10 nm) to the surface compared to a flat gold film in the conventional SPR setup. Moreover, the sensitivity was 8-fold higher with GSNPs than with gold nanospheres. This shows that relatively simple plasmonic nanostructures for LSPR-based sensing can be engineered to outperform conventional SPR, which is particularly interesting in the context of detecting low molecular weight compounds where a small sensing volume, reducing bulk signals, is desired.

  • 42.
    Martinsson, Erik
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Molekylär fysik. Linköpings universitet, Tekniska högskolan.
    Otte, Marinus A.
    Institut Catala de Nanociencia i Nanotecnologia (ICN2), Consejo Superior de Investigaciones Cientificas (CSIC) & CIBER-BBN, Campus UAB, Bellaterra, Barcelona, Spain.
    Shahjamali, Mohammad M.
    Northwestern University, Evanston, Illinois, USA.
    Sepulveda, Borja
    Institut Catala de Nanociencia i Nanotecnologia (ICN2), Consejo Superior de Investigaciones Cientificas (CSIC) & CIBER-BBN, Campus UAB, Bellaterra, Barcelona, Spain.
    Aili, Daniel
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Molekylär fysik. Linköpings universitet, Tekniska högskolan.
    Substrate Effect on the Refractive Index Sensitivity of Silver Nanoparticles2014Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 118, nr 42, s. 24680-24687Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The bulk refractive index (RI) sensitivity of dispersed and immobilized silver nanoparticles of three different shapes (spheres, cubes, and plates) is investigated. We demonstrate, both experimentally and theoretically, that the influence of immobilization on the RI sensitivity is highly dependent on the shape of the nanoparticles. A strong correlation is seen between the fraction of the particle surface area in direct contact with the substrate and the decrease in RI sensitivity when the particles are immobilized on a glass substrate. The largest decrease (−36%) is seen for the most sensitive nanoparticles (plates), drastically reducing their advantage over other nanoparticle shapes. The shape-dependent substrate effect is thus an important factor to consider when designing nanoplasmonic sensors based on colloidal noble-metal nanoparticles.

  • 43.
    Mastria, Rosanna
    et al.
    CNR NANOTEC Ist Nanotecnol, Italy; University of Salento, Italy.
    Rizzo, Aurora
    CNR NANOTEC Ist Nanotecnol, Italy.
    Giansante, Carlo
    CNR NANOTEC Ist Nanotecnol, Italy; UNILE, Italy.
    Ballarini, Dario
    CNR NANOTEC Ist Nanotecnol, Italy.
    Dominici, Lorenzo
    CNR NANOTEC Ist Nanotecnol, Italy; UNILE, Italy.
    Inganäs, Olle
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
    Gigli, Giuseppe
    CNR NANOTEC Ist Nanotecnol, Italy; University of Salento, Italy.
    Role of Polymer in Hybrid Polymer/PbS Quantum Dot Solar Cells2015Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 119, nr 27, s. 14972-14979Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Hybrid nanocomposites (HCs) obtained by blend solutions of conjugated polymers and colloidal semiconductor nanocrystals are among the most promising materials to be exploited in solution-processed photovoltaic applications. The comprehension of the operating principles of solar cells based on HCs thus represents a crucial step toward the rational engineering of high performing photovoltaic devices. Here we investigate the effect of conjugated polymers on hybrid solar cell performances by taking advantage from an optimized morphology of the HCs comprising lead sulfide quantum dots (PbS QDs). Uncommonly, we find that larger photocurrent densities are achieved by HCs incorporating wide-bandgap polymers. A combination of spectroscopic and electro-optical measurements suggests that wide-bandgap polymers promote efficient charge/exciton transfer processes and hinder the population of midgap states on PbS QDs. Our linings underline the key role of the polymer in HC-based solar cells in the activation/deactivation of charge transfer/loss pathways.

  • 44.
    Mickan, Martin
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska fakulteten. University of Lorraine, France.
    Stoffel, Mathieu
    University of Lorraine, France.
    Rinnert, Herve
    University of Lorraine, France.
    Helmersson, Ulf
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska fakulteten.
    Horwat, David
    University of Lorraine, France.
    Restoring the Properties of Transparent Al-Doped ZnO Thin Film Electrodes Exposed to Ambient Air2017Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 121, nr 27, s. 14426-14433Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The properties of Al-doped ZnO (AZO) films are known to degrade with exposure to humidity. Different AZO films deposited using reactive direct current magnetron sputtering (DCMS) and high power impulse magnetron sputtering (HiPIMS) have been aged in ambient laboratory conditions and annealed at temperatures between 160 and 180 degrees C in a N-2 atmosphere. Their electrical and optical properties, which have been investigated both ex situ and in situ during the annealing, are improved. The results of the in situ measurements are interpreted in terms of a diffusion process, where hydroxyl groups are decomposed and water is diffusing out of the films. As hydroxyl groups are known to act as a trap for charge carriers in ZnO, their removal from the film can explain the improvement of the electrical properties by the annealing.

  • 45.
    Nemec, H.
    et al.
    Nemec, H., Department of Chemical Physics, Lund University, Getingevdgen 60, 222 41 Lund, Sweden.
    Nienhuys, H.-K.
    Institute for Atomic and Molecular Physics, Kruislaan 407, 1098SJ Amsterdam, Netherlands.
    Zhang, Fengling
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik.
    Inganäs, Olle
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik.
    Yartsev, A.
    Department of Chemical Physics, Lund University, Getingevdgen 60, 222 41 Lund, Sweden.
    Sundstrom, V.
    Sundström, V., Department of Chemical Physics, Lund University, Getingevdgen 60, 222 41 Lund, Sweden.
    Charge carrier dynamics in alternating polyfluorene copolymer: Fullerene blends probed by terahertz spectroscopy2008Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 112, nr 16, s. 6558-6563Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Time-resolved terahertz spectroscopy is used for investigation of photoinduced charge carrier dynamics in blends of a polyfluorene copolymer (poly[2,7-(9,9-dioctyl-fluorene)-alt-5,5-(4',7'-di-2-thienyl- 2',1',3-benzo-thiadiazole)]) and an electron acceptor ([6,6]-phenyl-C61-butyric acid methyl ester). The transient far-infrared response appears instantaneously after photoexcitation. We show that the transient conductivity spectrum is dominated by two major contributions: response of separated charge carriers and response of coupled polaron pairs. © 2008 American Chemical Society.

  • 46. Nilsing, Mattias
    et al.
    Persson, Petter
    Lunell, Sten
    Ojamäe, Lars
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Fysikalisk Kemi.
    Dye-sensitization of the TiO2 rutile (110) surface by perylene dyes: Quantum-chemical periodic B3LYP computations2007Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 111, nr 32, s. 12116-12123Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The adsorption of perylene derivatives on the rutile TiO2(110) surface was studied by quantum-chemical periodic calculations employing the hybrid HF-DFT functional B3LYP. The perylene molecule, which is a possible constituent of dyes in dye-sensitized solar cells, was functionalized by attachment of phosphonic acid or carboxylic acid groups to permit anchoring to the metal oxide surface. The anchor groups were bound to the molecule directly or via different spacer groups, namely --CH2-, -CH2-CH2-, and -CH = CH-. The effects of the anchor and spacer groups on the adsorption geometry and energy, on the electronic structure of the dye-TiO2 interface, and on the electron transfer rates were investigated. The phosphonic acid anchor group was found to bind the perylene derivatives much more strongly to the surface than the carboxylic acid anchor group. The spacer groups were capable of significantly altering electron transfer rates across the dye-metal oxide interface, where the unsaturated groups permitted injection times in the low femtosecond regime.

  • 47.
    Näslund, Lars-Åke
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Ingason, Arni Sigurdur
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Holmin, Susanne
    Permascand AB, Ljungaverk, Sweden; Mid Sweden University, Sundsvall, Sweden.
    Rosén, Johanna
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Formation of RuO(OH)(2) on RuO2-Based Electrodes for Hydrogen Production2014Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 118, nr 28, s. 15315-15323Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The catalytic and durable electrode coating of ruthenium dioxide (RuO2), applied on nickel (Ni) substrates, is today utilized as electrocatalytic cathodes for hydrogen production, e.g., in the chlor-alkali process and alkaline water electrolysis. The drawback is, however, the sensitivity to reverse currents obtained during power shutdowns, e.g., at maintenance, where the RuO2-based electrodes can be severely damaged unless polarization rectifiers are employed. Through the material characterization techniques X-ray diffraction and X-ray photoelectron spectroscopy, we can now reveal that RuO2 coatings, when exposed to hydrogen evolution at industrially relevant conditions, transforms into ruthenium oxyhydroxide (RuO(OH)(2)). The study further shows that as the hydrogen evolution proceeds the formed RuO(OH)(2) reduces to metallic ruthenium (Ru).

  • 48.
    Näslund, Lars-Åke
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Sánchez-Sánchez, Carlos M.
    University of Alicante, Spain .
    Ingason, Arni Sigurdur
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Bäckström, Joakim
    Permascand AB, Ljungaverk, Sweden.
    Herrero, Enrique
    University of Alicante, Spain .
    Rosén, Johanna
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Holmin, Susanne
    Permascand AB, Ljungaverk, Sweden.
    The Role of TiO2 Doping on RuO2-Coated Electrodes for the Water Oxidation Reaction2013Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 117, nr 12, s. 6126-6135Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Electrochemical water splitting into H-2 and O-2 presents a significant and challenging energy loss due to the high overpotential required at the anode. Today, in industrially relevant applications, dimensionally stable anodes (DSA) based on the electrocatalytic active RuO2 are conventionally utilized. To enhance the resistance against corrosion, incorporation of TiO2 in the RuO2-coated electrodes is widely employed. In the present work we have used scanning electrochemical microscopy (SECM) to demonstrate that TiO2-doped RuO2-coated electrodes, in addition to being more durable, also show an electrocatalytic activity that is, on average, 13% higher as compared to the pure RuO2-coated electrodes. We also demonstrate that cracks in the pure RuO2 coating are the most active zones, probably because Ti from the Ti support has diffused into the first applied layer of the RuO2 coating. To reveal the nature of this enhanced activity for water oxidation displayed on TiO2-doped RuO2 electrodes, we have employed X-ray photoelectron spectroscopy (XPS) for material characterization. The results show that the electrocatalytic activity enhancement displayed on the mixed (Ru1-x:Ti-x)O-2 coating is promoted through a charge transfer from the RuO2 to the TiO2, which provides new and more reactive sites designated as activated RuO2 delta+.

  • 49.
    Oliveira, M. I. A.
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska högskolan. University of Federal Bahia, Brazil .
    Rivelino, R.
    University of Federal Bahia, Brazil .
    de Brito Mota, F.
    University of Federal Bahia, Brazil .
    Gueorguiev, Gueorgui Kostov
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Optical Properties and Quasiparticle Band Gaps of Transition-Metal Atoms Encapsulated by Silicon Cages2014Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 118, nr 10, s. 5501-5509Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Semiconductors assembled upon nanotemplates consisting of metal-encapsulating Si cage clusters (M@Si-n) have been proposed as prospective materials for nanodevices. To make an accurate and systematic prediction of the optical properties of such M@Si-n clusters, which represent a new type of metal silicon hybrid material for components in nanoelectronics, we have performed first-principles calculations of the electronic properties and quasiparticle band gaps for a variety of M@Si-12 (M Ti, Cr, Zr, Mo, Ru, Pd, Hf, and Os) and M@Si-16 (M = Ti, Zr, and Hf) clusters. At first stage, the electronic structure calculations have been performed within plane-wave density functional theory in order to predict equilibrium geometries, polarizabilities, and optical absorption spectra of these endohedral cagelike clusters. The quasiparticle calculations were performed within the GW approximation, which predict that all of these systems are semiconductors exhibiting large band gaps. The present results have demonstrated that the independent-particle absorption spectra of M@Si-n, calculated within the local density or generalized gradient approximations to density functional theory, are dramatically influenced by many-body effects. On average, the quasiparticle band gaps were significantly increased, in comparison with the independent-particle gaps, giving values in the 2.45-5.64 eV range. Consequently, the inclusion of many-body effects in the electron electron interaction, and going beyond the mean-field approximation of independent particles, might be essential to realistically describe the optical spectra of isolated M@Si-n clusters, as well as their cluster-assembled materials.

  • 50.
    Oliveira, Micael J. T.
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska högskolan. University of Coimbra, Portugal.
    Medeiros, Paulo V. C.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Beräkningsfysik. Linköpings universitet, Tekniska högskolan.
    Sousa, Jose R. F.
    University of Coimbra, Portugal .
    Nogueira, Fernando
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska högskolan. University of Coimbra, Portugal.
    Gueorguiev, Gueorgui Kostov
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska högskolan.
    Optical and Magnetic Excitations of Metal-Encapsulating Si Cages: A Systematic Study by Time-Dependent Density Functional Theory2014Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 118, nr 21, s. 11377-11384Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A systematic study of the optical and magnetic excitations of 12 MSi12 and four MSi10 transition metal encapsulating Si cages has been carried out by employing real time time-dependent density functional theory. Criteria for the choice of transition metals (M) are clusters stability, synthesizability, and diversity. It was found that both the optical absorption and the spin-susceptibility spectra are mainly determined by, in decreasing order of importance, (1) the cage shape, (2) the group in the Periodic Table to which M belongs, and (3) the period of M in the Periodic Table. Cages with similar structures and metal species that are close to each other in the Periodic Table possess spectra sharing many similarities; for example, the optical absorption spectra of the MSi12 (M = V, Nb, Ta, Cr, Mo, and W), which are highly symmetric and belong to groups 4 and 5 of the Periodic Table, all share a very distinctive peak at around 4 eV. In all cases, although some of the observed transitions are located at the Si skeleton of the cages, the transition metal species is always significant for the optical absorption and the spin-susceptibility spectra. Our results provide fingerprint data for identification of gas-phase MSi12 and MSi10 by optical absorption spectroscopy.

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