bluuebunny/crossref_metadata_2025_split huggingface dataset:
Insights into OLED functioning through coordinated experimental measurements and numerical model simulations
Authors: Berner D. , Houili H. , Leo W. , Zuppiroli L. 
Published: December 2004

AbstractApplying this method to the standard OLED device structure that has received broad attention in the literature, we have found a number of surprising results. From our experiments, we have demonstrated that the average electric field inside the hole transport layer is larger than or equal to the average field in the emission layer over the entire current range. The device simulations fully clarify the situation, giving insight into the space charge effects as well as the hole and the electron current distributions in the device. In particular, we found that there is a leakage of unrecombined holes towards the cathode at low voltages. We also found a strong variation of the electric field in the Alq3 layer due to space charge effects. By using the laser dye derivatives DCM‐TPA with electron trapping capabilities and DCM‐II with both electron and hole trapping capabilities as dopants in a standard OLED architecture, we could study the effect on transport and emission characteristics. In the case of the exclusively electron trapping dopant, a blue‐shift of the emission color with increasing bias is observed which we find is due to a splitting of the recombination zone.Applying this method to the standard OLED device structure that has received broad attention in the literature, we have found a number of surprising results. From our experiments, we have demonstrated that the average electric field inside the hole transport layer is larger than or equal to the average field in the emission layer over the entire current range. The device simulations fully clarify the situation, giving insight into the space charge effects as well as the hole and the electron current distributions in the device. In particular, we found that there is a leakage of unrecombined holes towards the cathode at low voltages. We also found a strong variation of the electric field in the Alq3 layer due to space charge effects. By using the laser dye derivatives DCM‐TPA with electron trapping capabilities and DCM‐II with both electron and hole trapping capabilities as dopants in a standard OLED architecture, we could study the effect on transport and emission characteristics. In the case of the exclusively electron trapping dopant, a blue‐shift of the emission color with increasing bias is observed which we find is due to a splitting of the recombination zone.
A review of electron–phonon coupling seen in the high‐Tc superconductors by angle‐resolved photoemission studies (ARPES)
Authors: Cuk T. , Lu D. H. , Zhou X. J. , Shen Z.‐X. , Devereaux T. P. , Nagaosa N. 
Published: December 2004

AbstractThis issue of pss (b) – basic solid state physics contains a collection of Review Articles on the rather controversially discussed topic of Electron–Phonon Interaction in High‐Temperature Superconductors, guest‐edited by Miodrag Kulić, Johann Wolfgang Goethe‐Universität Frankfurt/Main, Germany, with a Preface written by V. L. Ginzburg and E. G. Maksimov [1].The cover picture, taken from the review [2] by T. Cuk et al., shows plots of the electron–phonon coupling vertex, g2(k, k′), where k, k′ are the initial and final electron momentum for electrons scattered by the bond‐buckling phonon B1g (the out‐of‐phase vibration of the in‐plane oxygen) in a tight‐binding model of the copper–oxygen plane. The momentum dependence of this vertex, along with the d‐wave superconducting gap and the van Hove singularity at the anti‐node, accounts for the momentum dependence of the collective mode coupling seen in angle‐resolved photoemission data on Bi2212.The present issue also sees the start of our rapid research letters, the fastest peer‐reviewed publication medium in solid state physics. For more information see www.pss‐rapid.com and the Editorial by the Editor‐in‐Chief Martin Stutzmann on page 7 [3].
Microwave‐Assisted Synthesis of Pyrimidine Libraries
Authors: Bagley Mark C. , Hughes David D. , Lubinu M. Caterina , Merritt Eleanor A. , Taylor Paul H. , Tomkinson Nicholas C. O. 
Published: December 2004

AbstractDi‐ or trisubstituted pyrimidine libraries are prepared in good yield by the microwave irradiation of an alkynone and either an amidine or guanidine at 120–150 °C in acetonitrile in the presence of sodium carbonate or at 100 °C after treatment with methanolic sodium methoxide in a sealed tube using a monomodal microwave synthesiser. These rapid and efficient methods often require no chromatographic purification and so are appropriate for automated combinatorial methodology and have been applied in the synthesis of a small library of potentially useful novel ligands for the estrogen receptor based on the pyrimidine template.
Solid Phase Synthesis of 2‐substituted Melatonin Derivatives via Palladium‐mediated Coupling Reactions using Microwave Irradiation
Authors: Berthault Aurélie , Berteina‐Raboin Sabine , Finaru Adriana , Guillaumet Gérald 
Published: December 2004

AbstractA comparative study between conventional thermal and microwave assisted procedures on solid support to generate pharmacomodulated melatonin analogues using Stille, Sonogashira, Heck and Suzuki palladium mediated reaction.
Rapid Access to a Pentacyclic Library Core Structure: A Microwave Assisted Approach
Authors: Patterson Stephen , Lorenz Christiane , Slawin Alexandra M. Z. , Westwood Nicholas J. 
Published: December 2004

AbstractHigh throughput synthetic chemistry continues to develop in response to the challenges set by the genome projects. The ability to prepare large numbers of potentially bioactive compounds requires both technology and robust chemistry. Synthetic approaches that combine the use of microwave irradiation with facile isolation of products are therefore of importance. Here we describe a flexible approach to highly functionalised pentacyclic structures using microwave techniques. A range of pentacycles differing both in substituent patterns and ring size are prepared to exemplify the approach. Rapid access to these structures paves the way for the synthesis of libraries based on these cores.
Microwave Assisted Domino Knoevenagel Condensation/6π‐electron Electrocyclization Reactions for the Rapid and Efficient Synthesis of Substituted 2H,5H‐pyrano[4,3‐b]pyran‐5‐ones and Related Heterocycles
Authors: Leutbecher Heiko , Conrad Jürgen , Klaiber Iris , Beifuss Uwe 
Published: December 2004

AbstractBoth natural and unnatural compounds with a 2H,5H‐pyrano[4,3‐b]pyran‐5‐one skeleton are of interest to medicinal chemistry as they exhibit several different biological activities. This heterocyclic ring systems is accessible by a Domino Knoevenagel condensation/6π‐electron electrocyclization. A simple and rapid microwave assisted protocol of this Domino process has been developed for the preparation of libraries of substituted 2H,5H‐pyrano[4,3‐b]pyran‐5‐ones and related heterocyclic systems in a single preparative step by reaction of an α,β‐unsaturated aldehyde with a 6‐substituted 4‐hydroxy‐2H‐pyran‐2‐one.
Indirect Coupling of the 2(1H)‐pyrazinone Scaffold with Various (oligo)‐saccharides via “click chemistry”: en route towards Glycopeptidomimetics
Authors: Ermolat'ev Denis , Dehaen Wim , Van der Eycken Erik 
Published: December 2004

AbstractThe indirect coupling via a 1,2,3‐triazole ring system, of the 2(1H)‐pyrazinone scaffold with various saccharides is described. A microwave‐enhanced Cu(I)‐catalyzed Huisgen [2+3] dipolar cycloaddition reaction is applied. This opens the way for the generation of an interesting new class of glycopeptidomimetics.
XPS and Auger LMM analysis of ZnO/Si and ZnO/SiO2 interfaces
Authors: Raven M. S. 
Published: December 2004

AbstractThe interface between ZnO/Si and ZnO/SiO2 was studied by etching through the junction region and analyzing XPS and Auger LMM spectra. By comparing XPS shifts and peak splitting in the Si2p spectra, chemical complexes of the form Si—Ox—Zn (x≃1) were identified at the ZnO/Si interface. The transition from ZnO/SiO2 was characterized by intensity variations in the O1s spectra. Relative to metallic zinc the Auger LMM shifts were −4 eV for ZnO on Si and −3 eV for ZnO on SiO2. Such shifts were attributed mainly to extra‐atomic relaxation. Correspondence of levels (zero Auger shifts) was observed in the spectra from the two interface regions suggesting that zinc extra‐atomic relaxation was constant throughout a region of varying chemical composition.
Surface analysis of aromatic polyimide films using ESCA
Authors: Leary H. J. , Campbell D. S. 
Published: December 2004

AbstractC 1s, N 1s and O 1s core spectra were measured for well‐cured polyimide films of poly(N,N′‐(p,p′‐oxydiphenylene)promellitimide), and of poly(p,p′‐oxybis(phenylene)‐3,3′,4,4′‐benzophenonetetracarboxylimide). Resolvable were: multiple C 1s, two N 1s and two O 1s components. A carbonyl deficiency not due to X‐ray‐induced decarboxylation was detected. Approximately 45% of the surface carbon matrix was found to be comprised of partially oxidized, non‐carbonyl‐containing moieties of unknown origin. C 1s chemical shift behavior showed that imide bond formation does occur on curing; the imidization reaction in the surface region is incomplete (or altered) based on the changes in the O 1s and N 1s data with increasing temperature of curing. A surface chemical structure inconsistent with the bulk structural formula is observed.
Electron beam effects in Auger electron spectroscopy and scanning electron microscopy
Authors: Fontaine J. M. , Duraud J. P. , Le Gressus C. 
Published: December 2004

AbstractElectron beam effects on Si(100) and 5% Fe/Cr alloy samples have been studied by measurements of the secondary electron yield δ, determination of the surface composition by Auger electron spectroscopy and imaging with scanning electron microscopy. Variations of δ as a function of the accelerating voltage Ep (0.5<Ep<5 ke V), of the spot diameter ϕ (1 μm<ϕ<200 μm) and of the electron bombardment time t can be represented by simple expressions. The variations mainly affect the very low energy range of the n(E) distribution and correspond to volume phenomenon and surface effect. Impurities diffusing into or out of the irradiated regions cause changes in the contrast of scanning electron microscopy images at low bombardment levels. In contrast, the Auger electron spectroscopy peaks are modified only at high damage levels. The residual vacuum lower than 10 −9 Torr has no effect on technological samples covered with their reaction layers; the sensitivities to the beam depend rather on the earlier mechanical, thermal and chemical treatment of the surfaces.
The use of a new inelastic electron tunnelling spectrometer in the study of isomers of benzenedicarboxylic acid
Authors: Oxley D. P. , Bowles A. J. , Horley C. C. , Langley A. J. , Pritchard R. G. , Tunnicliffe D. L. 
Published: December 2004

AbstractA spectrometer is described with particular reference to its resolution and to a novel quick change specimen holder. For the benefit of new workers in the field, the need for four‐point probe measurements is reiterated, together with the importance of suitable cleaning procedures during sample preparation and rigorous electrical screening of the spectrometer. A high resolution spectrum of benzoic acid is presented together with spectra of 1,2‐, 1,3‐ and 1,4‐benzenedicarboxylic acids. Brief mention is made of the use of a computer data acquisition system with the latter, full details being described elsewhere.
The dependence on the angle of incidence of the steady state sputter yield of silicon bombarded by oxygen ions
Authors: Warmoltz N. , Werner H. W. , Morgan A. E. 
Published: December 2004

AbstractThe increased dependence of the sputter yield of silicon on the angle of incidence under oxygen ion bombardment, as compared to argon ion bombardment, observed during a SIMS analysis is discussed. Taking into account that the sputter yield depends on the implanted oxygen concentration, a relation is derived between the steady state sputter yield and the implanted oxygen surface concentration for different angles of incidence. Since this relation is in itself insufficient to determine the steady state values of the sputter yield and the surface concentration actually obtained, a graphical method is used to combine it with a second one, viz. the dependence of the momentary sputter yield on the momentary surface concentration. Measurements of the steady state sputter yield of silicon, bombarded by oxygen ions in the lower keV range at different angles of incidence, agree with the predicted values.
Quantitative depth profiling in surface analysis: A review
Authors: Hofmann S. 
Published: December 2004

AbstractAfter a brief survey of the various non‐destructive and destructive methods used for obtaining in‐depth composition profiles, the generally applicable method of ion sputtering in combination with a surface analysis technique is discussed in more detail. The quantitative evaluation of sputtering profiles requires the conversion of a measured signal intensity versus sputtering time into a true concentration versus distance from the original surface. Basically, this procedure comprises the quantification of the surface analysis method applied and the sputtering rate, both being dependent on sample composition. Furthermore, various phenomena limit the quantitative evaluation of depth profiles; the most important of which are ion and/or electron beam induced changes of surface composition and surface microtopography. Different factors such as information depth, ion beam inhomogeneity, original and beam induced roughness, knock‐on and atomic mixing effects, preferential sputtering, enhanced atomic migration etc. are discussed with respect to their influence on depth resolution and its dependence on sputter depth. Model calculations and their comparison with experimental data reveal the influence of these factors. In conclusion, the basic requirements for the optimization of sputter profiling are stated.
XPS and AES study of antimony oxides
Authors: Garbassi F. 
Published: December 2004

AbstractXPS and AES have been applied to the surface analysis of antimony oxides, Sb2O3, Sb2O4 and Sb2O5. By means of the computer‐operated separation of oxygen and antimony contribution, the oxygen to metal atomic ratios calculated from XPS data were found to be close to the expected values. An antimony powder sample was found to be covered by a surface layer of Sb2O4 and the variations in shape of Auger MNN peaks of Sb during depth profiling are shown and discussed.
Results of a Ta2O5 sputter yield round robin
Authors: Bevolo A. J. 
Published: December 2004

AbstractThe ASTM E42.08 subcommittee on ion beam sputtering has sponsored a round robin to measure the sputter yield of anodic Ta2O5 films grown on tantalum. The purpose of this study was to compare the results from different laboratories and to test the suitability of this material as a standard for sputter yield measurements. Six different laboratories made 42 separate measurements of the sputter yield of Ta2O5 by determining the time to the Ta2O5/Ta interface during Auger depth profiles using 2 ke V Ar+ ions. The scatter of an individual set of measurements varied from 3 to 6% (except for one laboratory) while the means of the individual set of measurements varied about 10% from the average of all of the measurements. This result indicated the presence of systematic errors among the various laboratories. The possible sources of these errors are discussed.
Ion scattering spectrometry: A versatile technique for a variety of materials
Authors: Baun W. L. 
Published: December 2004

AbstractThe extraordinary surface sensitivity of low energy ion scattering spectrometry may be applied to the characterization of a wide variety of materials. On the one hand, the surface chemistry may be determined, using ion scattering spectrometry for engineering materials used in diverse technologies such as lubrication and adhesive bonding; such surface chemistry, perhaps involving only a few monolayers, may govern the success or failure of a process. On the other hand, ion scattering spectrometry is also useful in investigating the chemistry and physical and electronic structure of single crystals. The presence of fine features in the spectra enable shadowing and selective neutralization effects to be observed. Striking spectral features are seen in III–V, II–VI, and I–VII compounds. Scattered ion yield curves show a potential for the use of ion scattering spectrometry to determine bonding and electronic structure in some elements. In addition, conventional scattering experiments may be used to determine subtle elemental changes on crystal faces having different orientations. Adsorption‐desorption characteristics of different orientations may also be studied in conjunction with the complementary secondary ion mass spectrometry technique.
The depth dependence of the depth resolution in sputter profiling
Authors: Werner H. W. 
Published: December 2004

AbstractIt is shown that data from different authors on the depth dependence of the depth resolution can be compared only when both the instrumental parameter (β) and the intrinsic parameter (α) are taken into account. These two essential parameters are shown to be unique for every given ‘set of instrument and sample’. A linear z‐dependence was derived in a first approximation from experimental data. In this case it is shown that a power approximation in a (log (Δz/z)vs log z) plot, can have any value for the exponent between −1 and 0, dependent on the z‐interval considered. The z‐interval for which a given value of the exponent is obtained, in turn depends on α and β. The influence of the acceptance area and the primary ion energy on the intrinsic parameter α and the influence of the beam inhomogeneity on the parameter β are discussed. The implications of a non‐linear z‐dependence on the interpretation of experimental data are considered.
Electron inelastic mean free paths in several solids for 200 eV ⩽ E ⩽ 10 keV
Authors: Ashley J. C. , Tung C. J. 
Published: December 2004

AbstractValues of k and p are given for predicting inelastic mean free paths for electrons with energies from 200 eV to 10 keV from the simple formula λ = kEp, based on theoretical calculations for ten elemental and compound solids. These results indicate that in the energy range 400 eV ⩽ E ⩽ 2000 eV, the value of p lies in the range 0.65–0.80. For Si and SiO2, presentation of the available experimental data and theoretical results illustrate the differences which exist in the values of electron mean free paths.
X‐ray photoelectron spectra of the U 4f levels in UF4, UF5 and UF6
Authors: Trowbridge L. D. , Richards H. L. 
Published: December 2004

AbstractUF6, UF5 and UF4 have been studied by X‐ray photoelectron spectroscopy. U 4f7/2 binding energies for these compounds were observed to be 384.9, 383.4 and 382.3 eV, respectively. The corresponding U 4f5/2 energies were 395.7, 394.2 and 393.2 eV. Solid UF6 was formed by condensation of a molecular beam onto Ni and Cu substrates at −80° C. UF4 was produced by reaction of the UF6 beam at higher substrate temperatures (−30° C and 25 °C). UF5 was produced at higher temperature and pressure by reaction of Cu and UF6. In the X‐ray photoelectron spectroscopy vacuum chamber, the UF5 converted slowly to UF4, probably by disproportionation and loss of UF6.
Multilayer analysis of ion implanted GaAs using spectroscopic ellipsometry
Authors: Erman M. , Theeten J. B. 
Published: December 2004

AbstractThe large number of independent data measured by spectroscopic ellipsometry as well as the marked optical contrast between the amorphous and crystalline state of GaAs are the basic reasons for the feasability of a multilayer analysis from the ellipsometric data taken on an ion implanted GaAs sample. The mathematical method and its limitations (convergence, influence of noise and systematic errors) are discussed. It is illustrated with the case of 10 ke V B+ ions implanted in GaAs (100) at room temperature at a dose of 1014 ions cm−2. The depth profile of lattice damage is obtained and discussed. The effect of thermal annealing up to 400° C is also examined.
Topographic images of supported catalysts
Authors: Gómez A. , Hernández P. , José‐Yacamán M. 
Published: December 2004

AbstractThe topographic mode of imaging has been used to study the systems Pd on graphite, Pt on graphite and Pt on alumina. It is shown that this method can provide information on the shape of the particles, on the morphology of the substrates (including steps on their surfaces) and on the distribution of the particles with respect to substrate features. It is also shown that with this method particles can be detected which, due to their smallness and to the presence of substrate noise, are otherwise invisible.
Fast atom bombardment mass spectrometry for applied surface analysis
Authors: Surman D. J. , van den Berg J. A. , Vickerman J. C. 
Published: December 2004

AbstractFast atom bombardment mass spectrometry permits the detection of secondary ions from surfaces of insulator materials without the necessity for charge neutralization of the surface by electron bombardment. It thus opens the possibility of routine mass spectral analysis of surfaces yielding data concerning not only their elemental composition but also their chemical structure. The possibilities are illustrated from examples of the analysis of glass and catalyst surfaces.
AES investigations of chemical composition of some alkali compounds
Authors: Dolizy P. , Grolière F. 
Published: December 2004

AbstractAuger electron spectroscopy is used as a quantitative and qualitative tool to investigate solid surfaces. Conventional quantitative analyses are based on the comparison of the Auger signal from the sample to that from pure standard. A detailed analysis of peak shape of Auger signal shows that the upper part of the derived Auger line (lower energy side) is strongly related to the chemical bonding whereas the lower part (high energy side) is nearly insensitive to the chemical effects.A calibration method for quantitative Auger spectroscopy based on the amplitude variation of the LVV Auger transitions of one element as a function of its chemical bonding within the compound is described. This method takes into account sample ‘matrix’ effects as well as all kinds of instrumental effects on the measured Auger signal.It has been also shown that AES can be used to make successful chemical analyses on alkali antimonides. A direct relation between electronic charge transfer between atoms and Auger peak shape has been observed, it is used to relate photoelectric quantum yield of SbKx compound to the ionicity of the Sb–K bond.
XPS and AES quantitative surface analysis: Comparison on oxide powder systems
Authors: Garbassi Fabio 
Published: December 2004

AbstractXPS and AES quantitative surface analyses on several oxide systems, containing two or three metal elements, are compared. Both single‐phase and multi‐phase systems have been investigated, representative of a variety of situations regarding surface v. bulk composition relationships. Metal‐to‐metal ratios obtained via the two techniques have been compared. A very intimate intermixing of cations, as it happens in single‐phase systems (i.e. solid solutions), appears a necessary but not sufficient condition for obtaining good correlation between the results of the two spectroscopies. Slopes of the straight lines correlationg XPS and AES data are generally far from the expected value of 1, suggesting the existence of strong matrix effects for at least one of the two techniques.