bluuebunny/crossref_metadata_2025_split huggingface dataset:
An alternative method for simultaneously measuring cell parameters of a twisted‐nematic liquid crystal cell
Authors: Chen Kun‐Huang , Chen Jing‐Heng , Lin Jiun‐You , Su Der‐Chin , Su Jung‐Chieh 
Published: February 2008

AbstractA phase‐sensitive method is developed to simultaneously measure the cell parameters of a TNLC (twisted‐nematic liquid crystal) cell based on Jones calculus and the heterodyne interferometric ellisometry. These cell parameters include the twist angle, the cell gap, and the angle of the entrance LC director. When a circularly polarized heterodyne light beam normally passes through a TNLC cell, the phase difference between the p ‐ and s ‐ polarization of the interference signal can be measured accurately with an analyzer and the heterodyne interferometric ellisometry. The phase difference de‐ pends on the azimuth angle of the analyzer and the parameters. By substituting the measured values of the phase differences at three different azimuth angles of the analyzer into the special equations derived with Jones calculus. Hence these three parameters can be estimated by using a personal computer with numerical analysis technique. Because of its common path optical configuration and its heterodyne interferometric ellisometry, this method has many merits such as high stability against the surrounding vibration, high resolution, and easy operation. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Spectroscopic ellipsometry and ellipsometric porosimetry studies of CVD low‐k dielectric films
Authors: Marsik P. , Verdonck P. , Schneider D. , De Roest D. , Kaneko S. , Baklanov M. R. 
Published: February 2008

AbstractAurora® ELK, a porous low‐k SiCOH film deposited by CVD, was used to study the effect of UV curing. Samples were cured for various curing times and the purpose of this work is to observe the effects of UV curing on optical, mechanical and structural properties of the low‐k film. We have used 1) ellipsometric porosimetry to determine the porosity and the pore‐size distribution and 2) nitrogen purged UV ellipsometry in a range from 2 to 9 eV to observe the changes of the dielectric function of the cured material. Additional FTIR and laser‐induced surface acoustic wave measurements were performed. The porogen removal and the increase of porosity were observed, and a k‐value of 2.3 was reached for the optimum curing time. However for longer curing times, densification and reduction of the porosity occurs. The growth of the hydrogen incorporation has been observed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Analysis of T. Lanuginosus lipase growth on octadecanthiol using surface plasmon resonance ellipsometry
Authors: Balevicius Z. , Vaicikauskas V. , Valincius G. , Ignatjev I. 
Published: February 2008

AbstractSurface plasmon resonance ellipsometry (SPRE) was used to investigate a multilayer system produced by Thermomyces Lanuginosus lipase (TLL) deposited from buffer solution onto chemically formed octadecanthiole (ODT) self‐assembled monolayer grown on a gold surface. The angular dependence of the ellipsometric parameters ψ and Δ was also investigated at a fixed wavelength (800 nm) when the TLL molecules were deposited on ODT from a buffer solution having a TLL concentration of 0.05 μM/L. Modelling the dependence of ψ and Δ on the angle of incidence using the Fresnel equations for a layered media showed that the system formed after 10 min can be imagined to be a two well defined layers: a self‐assembled ODT monolayer and a layer consisting of TLL and the buffer solution mixture. In the case of a system formed after 24 h, it was necessary to introduce an intermediate layer containing ODT and TLL molecules. The dependence of the ellipsometric parameters on angle measured at various wavelengths in the range from 750 nm to 950 nm demonstrated that the system formed in 24 h was more vitreous than a system formed in 10 min. It was concluded that for investigation of TLL and ODT molecules interaction by means of SPRE, the exposition time has to be taken into consideration. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Quantifying the accuracy of ellipsometer systems
Authors: Johs Blaine , Herzinger C. M. 
Published: February 2008

AbstractAs the diversity and complexity of ellipsometric applications continue to increase, so do the requirements for ellipsometric data accuracy. In the previous ICSE‐3 conference, Aspnes identified this issue, and suggested a 0.1% target for ellipsometric accuracy [1]. Unfortunately, there is no generally accepted method for characterizing or quantifying ellipsometric data accuracy. In this paper, a simple method and metric are proposed for quantifying the accuracy of an ellipsometer system. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Spectroscopic ellipsometry of anodized layer on single crystal InAsSb layer grown by melt epitaxy
Authors: Postava K. , Gao Y. Z. , Gong X. Y. , Halagačka L. , Pištora J. , Nakaoka A. , Yamaguchi T. 
Published: February 2008

AbstractAnodized layers on InAsSb, InSb, and InAs surfaces are characterized using phase modulation spectroscopic ellipsometry in a wide spectral range from 0.6 to 6.5 eV. Single crystal InAs0.04Sb0.94 layer was grown using melt‐epitaxy (ME). Optical properties of anodized layer prepared on InAsSb single crystal are compared with those on pure single crystals of InAs and InSb. Ellipsometric spectra of were fitted to the Tauc‐Lorentz model describing the anodizing layer optical functions. Clear tendency of ultraviolet shift of the band gap energy with decreasing antimony content is observed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical characterization of non‐stoichiometric silicon nitride films
Authors: Necas David , Perina Vratislav , Franta Daniel , Ohlídal Ivan , Zemek Josef 
Published: February 2008

AbstractCharacterizations of non‐stoichiometric silicon nitride films prepared by PECVD method onto silicon single crystal substrates are performed using variable angle spectroscopic ellipsometry and spectroscopic reflectometry and Rutherford backscattering spectrometry (RBS). The optical characterization employs a dispersion model based on the parametrization of the density of electronic states of the valence and conduction bands. The thin overlayers onto the upper boundaries of the films are taken into account. The values of the dispersion parameters of the SiNx films and thicknesses of these films and overlayers are determined. The ratios of Si and N atomic fractions in the individual films are evaluated using RBS. The results from the optical method and RBS are correlated. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Plasma flow induced local variation of dispersion constants of ITO‐films observed with spectroscopic imaging ellipsometry
Authors: Vaupel M. , Vinnichenko M. 
Published: February 2008

AbstractThe influence of the intentionally inhomogeneous plasma flow on the spatial distribution of the ITO optical properties has been investigated. The oscillator force has a minimum at low plasma flow and maxima at the high plasma flow regions of the sample. The free electron density increases at the edges of the wafer compared to the low plasma flow area of the sample. The changes are explained by varying the film microstructure and stoichiometry on macro‐ and microscopic scales. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
IR‐VIS‐UV ellipsometry, XRD and AES investigation of In/Cu and In/Pd thin films
Authors: Wronkowska A. A. , Arwin H. , Bukaluk A. , Skowroński Ł. , Trzcinski M. , Okulewicz K. , Wronkowski A. 
Published: February 2008

AbstractOptical and compositional properties of In, In/Pd and Pd/In/Pd thin films evaporated on Cu and SiO2 substrates in vacuum were investigated by means of X‐ray diffractometry, Auger electron spectroscopy and spectroscopic ellipsometry methods. Auger depth profile studies were performed in order to determine the composition of InCu and InPd structures. In both systems interdiffusion of metals was detected at room temperature. The XRD patterns indicated formation of CuIn2 and PdIn3 phases in the samples. Optical properties of the composite layers containing intermetallic phases were derived from ellipsometric quantities Ψ and Δ measured in the photon energy range 0.1‐6.0 eV at different angles of incidence using suitable multilayer models for the examined samples. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Mechanism for the gas‐phase reaction between OH and 3‐methylfuran: A theoretical study
Authors: Zhang Weichao , Du Benni , Mu Lailong , Feng Changjun 
Published: February 2008

AbstractThe mechanism for the OH + 3‐methylfuran reaction has been studied via ab initio calculations to investigate various reaction pathways on the doublet potential energy surface. Optimizations of the reactants, products, intermediates, and transition structures are conducted using the MP2 level of theory with the 6‐311G(d,p) basis set. The single‐point electronic energy of each optimized geometry is refined with G3MP2 and G3MP2B3 calculations. The theoretical study suggests that the OH + 3‐methylfuran reaction is dominated by the formation of HC(O)CHC(CH3)CHOH (P7) and CH(OH)CHC(CH3)C(O)H (P9), formed from two low‐lying adducts, IM1 and IM2. The direct hydrogen abstraction pathways and the SN2 reaction may play a minor or negligible role in the overall reaction of OH with 3‐methylfuran. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008
Whether proton transition to the triphosphate tail of ATP occurs at protein kinase environment: A Car‐Parrinello ab initio molecular dynamics study
Authors: Yang Sheng‐Yong , Zou Jun , Xiang Ming‐Li , Xie Guo‐Bin , Shi Bing , Wei Yu‐Quan 
Published: February 2008

AbstractProtonation state of the triphosphate tail of ATP (adenosine triphosphate) in protein environment is a fundamental issue, which has significant impact on the mechanism investigation of biochemical processes with ATP involved. Proton transition from surroundings (water molecule coordinating to magnesium, HW; amino group of Lys, HL) to the ATP tail in the catalytic core of protein kinase found recently disproved the commonly accepted deprotonation state of ATP tail. In this account, Car‐Parrinello ab initio molecular dynamics (CP‐AIMD) method has been employed to examine whether the proton transition occurs. To provide a comparison basis for the dynamics simulations, static quantum mechanics (QM), and combined quantum mechanics and molecular mechanics (QM/MM) calculations have also been carried out. Consistent results have been obtained that complete transition of hydrogen from the surroundings to the triphosphate tail of ATP is not allowed. The most dominant conformations correspond to the ones with HW bonding to O(W) and H‐bonding to O(ATP), [O(W)‐HW···O(ATP)], HL bonding to N(Lys) and H‐bonding to O(ATP), [N(Lys)‐HL···O(ATP)]. Metastable structures with one hydrogen atom bonding with two heavy atoms (hydrogen acceptors) were also located by our dynamic simulations. This bonding mode can satisfy the hungering for hydrogen of the two heavy atoms simultaneously. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008
Dissociation of a diatomic molecule induced by discontinuous reversals of a static electric field
Authors: Ghosh S. , Bhattacharyya S. P. 
Published: February 2008

AbstractA diatomic molecule modeled by a Morse oscillator is shown to undergo dissociation if the external electric field, in which the molecule is placed, undergoes discontinuous reversals. A threshold frequency of reversal is found to exist. The classical behavior is compared with its quantum counterpart. The mechanism of dissociation is analyzed. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008
Theoretical studies on the binding models of tetramethylammonium with phenol: Cation‐π and hydrogen‐bond interactions
Authors: Jiang Yanke , Wu Jun , Zou Jianwei , Lu Yunxiang , Hu Guixiang , Yu Qingsen 
Published: February 2008

AbstractA series of computations on the tetramethylammonium (TMA)‐phenol system were carried out with density functional theory (DFT) and Möller‐Plesset second order perturbation (MP2) methods at level of 6‐31+G**. The optimized structures obtained by the MP2 method are different from that obtained by the DFT method because of the influence of dispersion forces. Electron correlation contributes over 50% of total binding energy, and its influence on TMA–phenol system is similar to TMA–furan (50%) system, whereas much more significant than that in the TMA–imidazole (20%). Four different configurations for the TMA–phenol complex have been located. The interconverting barriers among the four binding models are less than 1 kcal/mol, significantly lower than those for the complex NH4+‐phenol. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008
Density functional theory study on hydrogen‐bonded complexes of adenine with polyformamide molecules
Authors: Tang Ke , Sun Haitao , Zhou Zhengyu , Wang Zhizhong 
Published: February 2008

AbstractThe structures of hydrogen‐bonded complexes A–Fn(n= 2–7) of adenine with polyformamide molecules have been fully optimized at B3LYP/6‐31G(d) basis set level. All the formamide molecules prefer to be NH proton donor rather than CH proton donor and are favorably bound to the five‐numbered moiety of adenine. A displacement of formamide molecules to one side of adenine mean plane has happened with an increasing number of formamide molecules. An obvious effect of hydrogen‐bonding cooperativity can be seen during the complex process. The most interesting geometrical change of adenine upon the complex is the shortening of the bond C4N6 resulting from the strengthening of the conjugation between the π system of the adenine ring and the lone pair of the nitrogen atom. An existence of weak NH···π bonding interaction between the π system of adenine and NH bond of F7 is found and further conformed by an natural bond orbital analysis specially carried out on A–F7. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008
Speciation of Energetic Materials on a Microcantilever Using Surface Reduction
Authors: Yi Dechang , Senesac Larry , Thundat Thomas 
Published: February 2008

AbstractAlthough microcantilevers have been used to detect explosives with extremely high sensitivity using variations in adsorption‐induced bending and resonance frequency, obtaining selectivity remains a challenge. Reversible chemoselectivity at ambient temperatures based on receptor‐based detection provides only limited selectivity due to the generality of chemical interactions. The oxygen imbalance in secondary explosives presents a means to achieve receptor‐free speciation of explosives using surface reduction of adsorbed molecules. We demonstrate highly selective and real‐time detection of Trinitrotoluene (TNT) using a copper oxide‐coated cantilever with a surface reduction approach. Not only can this technique exclusively differentiate explosives from nonexplosives, but also it has the potential to specify individual explosives such as TNT, pentaerythritol tetranitrate (PETN), and RDX. This technique together with receptor‐based detection techniques provides a multimodal approach for achieving very high selectivity. SCANNING 30: 000–000, 2008. © 2008 Wiley Periodicals, Inc.
Study of oxide protective layers on stainless steel by AES, EDS and XPS
Authors: Mandrino Djordje , Godec Matjaž , Torkar Matjaž , Jenko Monika 
Published: February 2008

AbstractA protective oxide layer was formed on the surface of stainless steel by standard industrial‐type thermal treatment. Additional post‐thermal treatment annealing and polishing followed by annealing were applied in an attempt to improve characteristics of the layers. Oxide layers formed on samples without and with different types of post‐thermal treatment processing were analysed and compared. Several techniques were employed. SEM was used to image the surface; AES, XPS and energy‐dispersive spectroscopy (EDS) were all used to probe the elemental composition of the oxide layers. AES was also used as the most straightforward method to obtain depth profiles. Low beam energy EDS was used in an attempt to obtain some fast averaged volume information from the layers. XPS was mainly used for determining chemical states on the surface of the sample but not for depth profiling (low sputtering rate due to large illuminated area). Analysed samples differed with regard to surface morphology of the oxide layers, oxide layer compositions and thicknesses. An attempt was made to relate these differences to differences in post‐thermal treatment procedures. Copyright © 2008 John Wiley & Sons, Ltd.
XPS characterization of a synthetic Ti‐containing MFI zeolite framework: the titanosilicalites, TS‐1
Authors: Langerame Fausto , Salvi Anna Maria , Silletti Marcello , Moretti Giuliano 
Published: February 2008

AbstractFollowing a previous investigation on micro‐ and mesoporous titanosilicates, we have here deepened the XPS and X‐ray‐excited Auger electron spectroscopy (XAES) studies on the surface properties of microporous titanosilicalites‐1 (TS‐1) and reference silicalites‐1 (S‐1), both characterized by the MFI framework type. The aim was that of complementing the information already obtained on these compounds with other techniques such as X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), dielectric relaxation spectroscopy (DRS), electron spin resonance (ESR), and quantomechanical calculations. Notwithstanding the expected low photoelectron intensity due to the very low solubility of Ti (IV) ions in the MFI framework, an accurate XPS curve‐fitting procedure and the simultaneous use of the XPS and Auger signals (Wagner plot) have made possible, both qualitatively and quantitatively, the distinction of two Ti (IV) sites: the framework tetrahedral species—Ti (IV) substituting Si (IV)—and the Ti(IV) tetrahedral species grafted to surface hydroxyl groups. Both species are prone to convert into octahedrally coordinated Ti (IV) species as a consequence of interaction with water and other ligands. Copyright © 2008 John Wiley & Sons, Ltd.
Carbide formation upon heat treatment of molybdenum layers deposited on carbon substrates: comparison of experimental data with a cellular automaton model
Authors: Kiniger M. , Eisenmenger‐Sittner C. , Hell J. , Schwarz B. , Hutter H. , Puchner S. 
Published: February 2008

AbstractManipulation of the adhesion of copper on carbon is crucial for the production of copper‐carbon composites as potential high‐performance heat sinks in electronic devices. A thin 100‐nm sputter‐deposited molybdenum (Mo) interlayer between copper and carbon increases adhesion significantly after thermal treatment. Mo layers of 100 nm have been sputter‐deposited on a plane of carbon substrate. SIMS measurements have been performed after rapid heating and subsequent thermal annealing of the samples at the temperatures 400, 500 and 600 °C for 1 min. While the carbon signal measured with SIMS in the Mo interlayer for the sample annealed at 400 °C is very low, a higher‐carbon signal at the interface has been detected after annealing at 500 °C. Annealing the sample at 600 °C yields a high‐carbon signal throughout the whole Mo interlayer resulting from the formation of Mo2C. A cellular automaton model for parallel carbon‐Mo layers has been designed in order to simulate the influence of the grain boundaries for the reaction and diffusion process. Comparing the results of the simulation and the experiment, the previously drawn assumption that grain boundary diffusion plays a crucial role for the growth kinetics of Mo2C at the Mo‐C interface could be corroborated. Copyright © 2008 John Wiley & Sons, Ltd.
Calculation of layer thickness on rough surfaces by polyhedral model
Authors: Mohai M. 
Published: February 2008

AbstractThe XPS intensity data are sensitive to the surface topography of the sample; implicitly or explicitly, a geometric model is always involved.Samples with rough surfaces, covered by thin overlayers, commonly occur in practice. The rough surfaces can be modelled with a set of small polyhedra. If the surface can be inspected visually, the area ratio of the planes of the polyhedra at different angles can be estimated or, in case of regular structure, can be calculated exactly. The intensity originating from the various planes of the sample is weighted by this ratio, taking into account the projected areas corresponding to different effective thickness values.In the latest version of the XPS MultiQuant program, the correction factor set can be freely edited and calculations can be conveniently performed on any type of polyhedron‐shaped samples. Copyright © 2008 John Wiley & Sons, Ltd.
Actual constitution of the mixed oxide promoter in a Rh/Ce1−xPrxO2−y/Al2O3 catalyst. Evolution throughout the preparation steps
Authors: Aboussaïd Karima , Bernal Serafín , Blanco Ginesa , Calvino José Juan , Cifredo Gustavo Aurelio , López‐Haro Miguel , Pintado José María , el Begrani Mohamed Soussi , Stéphan Odile , Trasobares Susana 
Published: February 2008

AbstractThe evolution of the ceria‐praseodymia mixed oxide promoter throughout the successive steps involved in the preparation of a 3% Rh/25% Ce0.8Pr0.2O2−x/Al2O3–3.5% SiO2 catalyst is studied with the help of X‐ray diffraction (XRD), spatially resolved electron energy loss spectroscopy (EELS), XPS, and thermal programed desorption (TPD) techniques. Incipient wetness impregnation has been used to obtain the appropriate loading of this promoter. As revealed by XRD, EELS, and XPS data, the alumina‐supported CeO2PrO2−x mixed oxide sample consisted of a bimodal distribution of the particles of the promoter. XRD shows two fluorite‐like phases: cerium‐rich particles with a mean crystallite size greater than 6 nm and smaller praseodymium‐rich crystals, about 3.5 nm size. Surface Ce/Pr ratio obtained by XPS was consistent with a higher dispersion of the praseodymium‐rich oxide particles. The final Rh catalyst was prepared in a second step, by impregnation of the CePrOx/Al2O3 system with an acidic solution of Rh(NO3)3. The low pH of this solution is responsible for further modifications of the lanthanide oxides distribution. Thus, there is a redispersion of the praseodymium‐rich phase, which is evidenced by EELS and XPS data. Likewise, CO2 desorption from samples exposed to the atmosphere is consistent with an enhanced basicity of the sample due to the increase of Pr3+ content at the surface of the catalyst. The observed changes on the nanostructure of the mixed oxide promoter can be attributable to a partial dissolution of the oxide, selectively leaching Pr3+ cations from the lattice, which are finally deposited as small particles after the drying steps of the preparation. Copyright © 2008 John Wiley & Sons, Ltd.