bluuebunny/crossref_metadata_2025_split huggingface dataset:
HCN: Hydrogen‐Bonded Versus Conjugated Polymer
Authors: Springborg Michael 
Published: July 2012

AbstractResults of a density‐functional study of linear HCN and CNH monomers, the corresponding hydrogen‐bonded polymers, and a conjugated polymer (CHN)x with C and N atoms alternating along a zigzag chain are reported. Minimizing the total energy as a function of structure results in realistic structures for the monomers and the conjugated polymer; but the local‐density approximation may be responsible for the too short hydrogen bonds found for the hydrogen‐bonded polymers. For the optimized structures we present electronic energies, densities of states, photoelectron spectra, momentum densities, and reciprocal form factors. Comparing these clearly demonstrates both similarities and differences for the various systems. It is further demonstrated that the conjugated polymer can lower the total energy upon a C–N bond‐length alternation. A model is then constructed with which solitons and polarons in the conjugated polymer are examined. Both types of structural defects are stable for the charged chains and induce two gap‐states. Finally, polarons in the hydrogen‐bonded chains are discussed.
Solid Phases from the Liquid System H2N(CH2)2NH2  CdBr2  HBr  H2O. An X‐ray and 79,81Br — NQR Study of (H3N(CH2)2NH3)CdBr4, (H3N(CH2)2NH3) (CdBr3)2 · H2O, and (H3N(CH2)2NH3)2CdBr6
Authors: Krishnan V. G. , Dou Shi‐Qi , Paulus Helmut , Weiss Alarich 
Published: July 2012

AbstractFrom the aqueous system ethylenediamine, (en),  CdBr2  HBr  H2O of varying component concentrations, at room temperature the compounds (enH2)CdBr4, (enH2)(CdBr3)2 · H2O, and (enH2)2CdBr6 were crystallized. 79,81Br NQR spectroscopy shows that the three solid phases, crystallized at room temperature, are the stable ones in the temperature range 77 ≤ T/K ≤ 300. (enH2)CdBr4 shows a three line 81Br NQR spectrum, the frequencies lying in the range 53 ≤ v (81Br)/MHz < 68 and having negative temperature coefficients dv/dt over the whole temperature range covered. A phase transition with hysteresis is observed at 340 K. In the high temperature phase I only one 81Br NQR line is observed, with negative temperature coefficient, too.(enH2)(CdBr3)2 · H2O shows also a three line 81Br NQR spectrum, the frequencies lying in the range 38 MHz to 72 MHz at room temperature with positive as well as negative temperature coefficients.(enH2)2CdBr6 reveals a four line 81Br NQR spectrum, three of the lines lying in the range 40 MHz to 70 MHz; the fourth line was observed at frequencies as low as 10 MHz. (enH2)(CdBr3)2 · H2O crystallizes at room temperature monoclinic, space group C2h6‐C2/c with Z = 4 (formula units per unit cell) a = 818 pm, b = 2413 pm, c = 801 pm, β = 107.8°. The structure is characterized by chains of units [Cd4Br12]4. The chains are built up by edge connected octahedra CdBr6 and the corners of two neighbouring octahedra are part of a bridging tetrahedron CdBr4, located alternating cis and trans on the chain. (enH2)2CdBr6 crystallizes also monoclinic, space group C2h2‐P21/m, a = 669 pm, b = 2050 pm, c = 637 pm, β = 93.4°; Z = 4. The structure corresponds to a formulation ((enH2))2(CdBr4)2⊖ · 2Br⊖. In both compounds hydrogen bonding is observed. The NQR results are in full agreement with the crystal structures; structure and bond scheme are discussed.
First Evidence of the Preformation of an Inorganic Network in Sol‐Gel Processing of Lead Zirconate Titanate, obtained by EXAFS Spectroscopy
Authors: Ahlfänger R. , Bertagnolli H. , Ertel T. , Kolb U. , Peter D. , Naß R. , Schmidt H. 
Published: July 2012

AbstractWe report the results of EXAFS spectroscopical investigations on lead zirconium titanium precursors in the sol and gel state. Analysis of the second coordination shell for both the sol and the gel yields the contribution of titanium backscatterers at a mean distance of 3.48 Å (sol) and 3.44 Å (gel). We draw the conclusion that a uniform composition on a microscopic scale exists in the sol as well as the gel state. In other words, heterocondensation is favoured against homocondensation. This provides a good explanation of the low calcination and sintering temperatures in the sol‐gel processing of lead zirconate titanate compared with other preparation techniques.
Temporal and Spatial Averaging Effects in Local Tropospheric Hydroxyl Determination
Authors: Armerding W. , Herbert A. , Comes F. J. 
Published: July 2012

AbstractThough the theory of the fast tropospheric photochemistry is well established its verification by experimental measurements e.g. of OH in the troposphere – including the simultaneous determination of all input parameters controlling the local chemistry – has not yet been achieved. The main reasons for this deficit are severe problems in realizing proper experimental procedures. The only accepted results in the past evolved from long path absorption measurements. But this method contains severe temporal and spatial averaging. In this paper we will discuss how to design a suitable experiment (based on model calculations) considering the temporal and spatial fluctuations of tropospheric trace gases and the resulting averaging problems.
Silicon Film Formation by Reaction of Active Hydrogen with Silane
Authors: Roth A. , Comes F. J. 
Published: July 2012

AbstractSilane is reacted with active hydrogen in a flow reactor. Thin silicon films are produced which are amorphous or μ‐cristalline, depending only on flow conditions. Growth rates of the films are between 3 and 6 Å/s. The transition from μ‐cristalline to amorphous behaviour is continuous. Treating the material with atomic hydrogen results in a substantial change of the film properties. Etching of the material is also observed and found different for μc‐Si: H compared to a‐Si:H.
Growth, Structure and Properties of Thin Films and Superlattice Structures
Authors: Sundgren Jan‐Eric 
Published: July 2012

AbstractThis paper addresses growth mechanisms, characterization and properties of thin films grown from the vapor phase. The emphasis is placed on artificial structures such as metastable alloys and layered materials, including superlattices. For metastable alloy formation it is demonstrated that a bombardment of the growing film surface by low‐energy ions can be used to promote growth of metastable alloys even at temperatures high enough for epitaxial films to form. In the case of layered materials it is shown using a combination of X‐ray diffraction and high resolution transmission electron microscopy, that superlattices with atomically sharp interfaces can be grown not only in the case of materials with covalent bonds (e.g., semiconductors) but also in the case of materials with metallic bonds. Finally, some properties of metallic superlattices are also discussed.
Ultrathin Films of Polymers Plenary Lecture
Authors: Wegner Gerhard 
Published: July 2012

AbstractThe Langmuir‐Blodgett technique provides for the possibility to prepare ultrathin layers of macromolecules on solid, planar substrates. In this context a series of novel polymers was synthesized and tested with the aim to develop the materials science background and the methodology to fabricate devices based on such ultrathin layers. This made it necessary to develop or adapt a number of methods to characterize these ultrathin layers at surfaces with regard to homogeneity, orientation phenomena, optical properties and transport behavior. The design of macromolecules described as “hairy‐rods” proved to be particularly successful and novel types of supramolecular architectures could be realized best described as “molecularly reinforced liquids”. First attempts to build prototype devices based on layered assemblies of these nonconventional polymers are mentioned.
Bindungsstruktur in plasmapolymerisierten Schichten aus Vinyltrimethylsilan
Authors: Kruse A. , Hennecke M. , Baalmann A. , Schlett V. , Stuke H. 
Published: July 2012

AbstractPlasma polymer films of vinyltrimethylsilane (VTMS) were deposited by radiofrequency (RF. 13.56 MHz) or Microwave (MW, 2.45 GHz) discharges in two reactors of the same volume and geometry.—The polymer films were characterized by electron spectroscopy for chemical analysis (ESCA) and infrared spectroscopy (FTIR). It turned out, that the RF—and the MW—polymers had almost the same Si/C‐composition ratio of 1/5 in the entire range of RF‐and MW‐power (60–150 W). Although the Si/C film‐composition remains almost constant, the binding states of Si‐and C‐atoms in the respective ESCA‐spectra are changing. While the CSi part of the C1s‐peak increases with the RF‐or MW‐power, the CH/CC part of the peak decreases, indicating a loss of hydrogen in the polymer films.—Obviously the fragmentation of the VTMS‐monomer is quite different for the two types of plasma discharges. While films of the RF‐plasma clearly show strong contributions of the methyl and vinyl groups, these groups are completely missing for the MW‐plasma polymers.—From these results structure models of the plasma polymers have been developed.
Membrane‐Properties of Polymer Films: The Acid‐Doping Reaction of Polyaniline
Authors: Asturias Gabriel E. , Jang Guang‐Way , Macdiarmid Alan G. , Doblhofer Karl , Zhong Chuanjian 
Published: July 2012

AbstractThe protonation/deprotonation reaction of polyaniline in the emeraldine oxidation state (PANI‐E) is discussed on the basis of membrane‐equilibrium considerations. The important role of the partitioning of H+ between the polymer and the bathing solution is pointed out. The concentration of (free) H+ in the polymer phase is used as a parameter in formulating the dissociation equilibrium of the Brønsted acid (PANI‐E)H+. It is shown that the pKa value determined for this dissociation equilibrium, pKa ≈ 5, is practically constant for all experimental conditions considered in this work. However, the pH of the bathing solution which leads to a defined protonation state of the PANI‐E may vary widely depending on the partitioning equilibrium for H+. This fact is demonstrated experimentally, and the experimental findings are shown to agree with theoretical predictions based on estimated and experimentally determined Donnan potentials.
Properties of Thin Palladium‐Films and Their Hydrogen‐Permeability
Authors: Züchner H. , Schlüter H.‐J. , Rauf T. , Hergemöller R. 
Published: July 2012

AbstractThin Pd films are used as protective layers against reoxidation of cleaned less noble metals in order to allow an easy hydrogen uptake. The hydrogen permeability through the Pd‐films into the substrate metal depends strongly on the film preparation conditions especially on the deposition rate and substrate temperature during deposition. Various measurements (including resistivity, electrochemical diffusion, SIMS and AES, gravimetrical and X‐ray diffraction measuring techniques) have been applied to characterize film samples prepared in different ways in order to find the optimal conditions to prepare protective but hydrogen permeable Pd‐films. It could be shown that the hydrogen uptake from the gas phase is mainly determined by adsorption layers on the film surface, additionally the hydrogen permeability is closely connected with the structure of the interface between film and substrate. Low deposition rates and increased substrate temperatures during preparation are the basis to obtain Pd‐films with best properties for an easy hydrogen uptake and permeability.
Layered Structures in Electrolessly Deposited Nickel/Phosphorus Films
Authors: Paletschek Axel , Ramiaramanana Patrick , Weil Konrad G. 
Published: July 2012

AbstractElectrolessly deposited nickel/phosphorus films with average phosphorus contents above 20 at% consist of a glassy matrix which contains variable amounts of fcc nickel crystals, supersaturated with phosphorus. The relative amounts of these crystalline inclusions can be varied widely when additives are present during the plating process. In earlier studies we could demonstrate that the crystalline inclusions were of columnar shape and extend through the whole film. In this paper we will report on experiments aimed at the finding of additives which lead to the formation of layered structures with subsequent predominantly crystalline and predominantly glassy layers.
Investigation of Rhodamine 6G Adsorption at the Fused‐Silica/Ethanolic Solution Interface Using Optical Second Harmonic Generation
Authors: Hill W. , Werner L. , Marlow F. 
Published: July 2012

AbstractAdsorption of rhodamine 6G molecules at the interface between fused‐silica and ethanolic solution is investigated by means of optical second harmonic generation (SHG). In internal reflection geometry, the SHG intensities as a function of angle of incidence exhibit characteristic points arising from beginning total reflection of both fundamental and harmonic waves. Curve shapes of SHG responses depend on dispersion and absorption of the solution. The fit of the angular dependences by an interface model taking into account complex refractive indices of the solution yields optical constants, which are necessary for the determination of surface concentration and orientation of the adsorbed molecules. A relation between tensor components of the nonlinear susceptibility of a layer of plate‐like molecules can be used for the calculation of a mean refractive index inside the layer, which leads to a more realistic determination of nutation angles of the molecules.
XPS and Electrochemical Studies of Thin TiN Layers
Authors: Siemensmeyer B. , Bade K. , Schultze J. W. 
Published: July 2012

AbstractTiN layers were prepared by implantation of 3 keV N2+ into Ti. The resulting layer thickness was 8 nm. Implantation, XPS and electrochemical studies were carried out in a closed system. Therefore no air oxidation took place between preparation and analysis. The electrochemical investigations (current, capacity, electron transfer and photoelectrochemical measurements) revealed the stability of TiN up to 1.3 V. At higher potentials oxidation to TiO2 and N2 dissolved in TiO2 took place. The reaction products could be detected with XPS. Sputter depth profiles revealed a layer structure Ti/TiN/TiO2. The layer thicknesses of TiO2 were smaller than on Ti at the same potentials. Photoelectrochemical experiments indicated similar electronic properties for the oxide layers on Ti and TiN. During oxidation no photocurrent was observed for TiN below 1.5 V. The stability of TiN against oxidation is explained by a N3‐ layer at the surface with a large electron density screening the underlying Ti ions and inhibiting oxidation.
Thin Pyrite Films Prepared by Sulphurization of Electrodeposited Iron Films
Authors: Pimenta G. , Schröder V. , Kautek W. 
Published: July 2012

AbstractA simple procedure for the production of pyrite (FeS2) thin films starting from the pure elements is presented. A pure, highly (110) oriented polycrystalline iron precursor layer could be successfully electrodeposited. Direct sulphurization of those films on Mo foils resulted in pyrite with (200) oriented grains embedded in a randomly oriented matrix. No other iron sulphide phase like e.g. marcasite was observed. XPS shows the presence of at least 97% FeS2. Depth profiles demonstrate the stoichiometric homogeneity across the films.
Surface Analysis Investigations on the Reaction of FeS2 with Alkali Metals
Authors: Bronold M. , Pettenkofer C. , Jaegermann W. 
Published: July 2012

AbstractThe reactions of cleaved (100) single crystal surfaces of FeS2 with in‐situ deposited lithium and potassium have been studied with X‐ray and ultraviolet photoelectron spectroscopy. Room temperature deposition of K leads to the formation of KFeS2 as has been verified by comparism with core level and valence band spectra of polycrystalline KFeS2. The reaction products formed by deposition of Li are thought to be Li2S and FeS. The results of the UHV experiments are compared to electrochemical measurements.
Metal‐Support Interaction in a Pt  TiO2 Thin Film System: Observation of the Pt3Ti Phase at 823 K
Authors: Lamber R. , Schulz‐Ekloff G. 
Published: July 2012

AbstractIt is shown by means of analytical electron microscopy that platinum dispersions on TiO2 (anatase) films form a Pt3Ti alloy under thermal treatment at 823 K in hydrogen. The formation of the Pt3Ti intermetallic compound is accompanied by the local reduction of the TiO2 support to titanium suboxides (Ti4O7).
Adsorption and Polymerization of Thiophene on a Ag(111) Surface
Authors: Baumgärtner K. M. , Volmer‐Uebing M. , Taborski J. , Bäuerle P. , Umbach E. 
Published: July 2012

AbstractThe adsorption and in‐situ polymerization of monothiophene on Ag(111) has been studied by X‐ray photoemission (XPS), programmed thermal desorption (TDP) and mass spectrometry. Thiophene is physisorbed on Ag(111) and desorbs entirely below 250 K. Three different desorption peaks representing multilayers and two different monolayer states can be distinguished by TPD. X‐ray irradiation leads to polymerization in multilayers which is accelerated by enhanced substrate temperatures, whereas the polymerization process is quenched at the Ag surface.
Etching Pretreatment and Galvanic Cu Enhancement of Laser‐Deposited Ultrathin Ni Structures on p‐Si
Authors: Sorg N. , Kautek W. , Paatsch W. 
Published: July 2012

AbstractDetailed investigations about the influence of pretreatment on the surface composition are presented. XPS data show that in 2 M NH4F radically etched Si is widely inert in respect to oxide formation at air: even after 1.5 h air contact, the oxidized Si is still less than 4 surface atom%. The same amount of oxide can be built up, however, by a 3 min contact with aqueous solution. This indicates the important role of water and humidity in the oxide formation at air.—A galvanic procedure to enhance photodeposited metal structures with a high lateral resolution is demonstrated. Cu can be electrodeposited in the dark restricted to this primary Ni structure. The thickness of the stripes could be enhanced by more than one order of magnitude while their width remained unchanged. This dark current process can only take place because the band bending has been reduced to such an extent that thermionic emission of electrons from the valence band to the metal is possible. This occurs exclusively under the metal (Ni) covered areas.
Isotope Effect in the Time Resolved Fluorescence of Anthracene in Small Unilamellar Vesicles
Authors: Brand K. , Hof M. , Schneider F. W. 
Published: July 2012

AbstractThe fluorescence decay of anthracene in small unilamellar vesicles (SUV) was determined employing a precise single photon counting technique. The fluorescence data were fitted best by a biexponential decay law. The longer component τ2 (4.75 ns at 26.0 °C) represents the decay time of anthracene being quenched by the lipid molecules. The shorter (red shifted) component τ1 (1.47 ns at 26.0 °C) displays a strong solvent (H2O/D2O) isotope effect. Therefore it is suggested that a number of H2O molecules may be present in the interior of the lipid bilayer. Both τ1 and τ2 processes display an apparent negative activation energy below the main phase transition which may be explained by a pre‐equilibrium whose ΔH0 is more negative than the positive activation energy of the subsequent emission step.
Investigations on Conducting Polymer Films with a Fast Electrochemical Quartz Crystal Microbalance
Authors: Dusemund C. , Schwitzgebel G. 
Published: July 2012

AbstractA fast electrochemical quartz crystal microbalance (EQCM) is presented, by means of which it is possible to obtain a resolution of a few nanograms within a measuring time of one millisecond. So, mass changes accompanying cyclic voltammetry (CV) of high scan rates as well as step experiments can be recorded.—The EQCM was used for the investigation of ion‐exchange properties of conducting polymers, especially polypyrrole, which was electropolymerised potentiodynamically onto gold in aqueous solution. The insertion and expulsion of counterions (anions and/or cations) during the electrochemical change of the oxidation state of the film was studied. From the mass change and the accompanying current the different contributions of the ions to the exchange could be determined.
Contraction of Small Features in Hardened Thin Films of Novolak
Authors: Köhler J. M. , Ritzel O. , Brodkorb W. , Dittrich P. 
Published: July 2012

AbstractThe geometry of sub‐half‐micron features of thin films of cross linked novolak, which are formed by a three‐layer‐resist process, is found to be dependant not only on the conditions of preparation, but on the feature size, too. Small features show a reduction of the expected height up to more than 30 per cent of the thickness of the original thin film. Smaller features are stronger contracted than larger. The contraction effect increases with decreasing curing time and curing temperature during the thermal cross linking process. It decreases with decreasing thermal stress during the reactive ion etching of the novolak film. There is assumed, that the effect depends on surface forces of small novolak features and the local mobility of polymer net work. The effect will become important in the further development of microlithographic technologies.
Plasma‐Etching of Nafion® and Deposition of Electrocatalysts by MOPECVD
Authors: Zylka D. , Schmeußer M. , Ledjeff K. 
Published: July 2012

AbstractCation exchange membranes are used as solid polymer electrolytes (SPE) for proton transport in special types of electrolysers and fuel cells. A good contact with the electrodes is necessary to achieve high efficiency. Therefore, surface treatment of the solid polymer electrolyte using a plasma etching process is investigated to create favourable conditions for the preparation of sufficient membrane electrocatalyst composites. Nafion® membranes are etched in a pulsed 27 MHz oxygen/argon plasma under different conditions. The adjustment of the plasma parameters determine the surface structure and properties of the membrane after the etching process.—With a view to coat membranes in future, a new coating technique for temperature sensitive substrates by means of an MOPECVD process is beeing developed. Platinum, ruthenium and tin organyls are decomposed in argon/hydrogen plasma to create metallic thin films. The plasma parameters RF‐power, pressure, electrode temperature and plasma gas mixture significantly affect the quality of metal films deposited using this technique. After the optimization of these parameters the production of films with conductivities corresponding to their bulk metals is now possible.
Growth of Thin Films of Lanthanide Oxides and Lanthanide Copper Oxides by MOCVD
Authors: Gerfin Tobias , Becht Michael , Dahmen Klaus‐Hermann 
Published: July 2012

AbstractThin films of CeO2, Nd2O3 and Nd2CuO4 were prepared by MOCVD on quartz, sapphire, MgO[100] and Si[100]. The usual β‐diketonato complexes were used as precursors. Preliminary information about the thermal stability and possible fragmentation of the precursors was obtained by thermal analysis and mass spectrometry. The good cristallinity of the films was demonstrated by XRD. In all three compounds a preferential orientation was found. The morphology and elemental distribution on the films was investigated by profilometry and EMPA. For the deposition of CeO2 films from the precursor Ce(dpm)4 a variety of carrier and reaction gases were investigated.