bluuebunny/crossref_metadata_2025_split huggingface dataset:
Alkyl Monolayer Passivated Metal–Semiconductor Diodes: 2: Comparison with Native Silicon Oxide
Authors: Liu Yong‐Jun , Yu Hua‐Zhong 
Published: April 2003

AbstractTo understand the electrical properties at passivated metal–semiconductor interfaces, two types of mercury–insulator–silicon (n‐type) junctions, Hg|C10H21Si and Hg|SiO2Si, were fabricated and their current–voltage and capacitance–voltage characteristics compared. Both of them exhibited near‐ideal rectifying characteristics with an excellent saturation current at reverse bias, which is in contrast to the previously reported ohmic behavior of an unmodified mercury–silicon junction. The experimental results also indicated that the n‐decyl monolayer passivated junction possesses a higher effective barrier height, a lower ideality factor (that is, closer to unity), and better reproducibility than that of native silicon oxide. In addition, the dopant density and build‐in potential, extracted from capacitance–voltage measurements of these passivated mercury–silicon junctions, revealed that alkyl monolayer derivatization does not alter the intrinsic properties of the silicon substrate. The calculated surface state density at the alkyl monolayer|silicon interface is lower than that of the silicon oxide|silicon interface. The present study increases the possibility of using advanced organic materials as ultrathin insulator layers for miniaturized, silicon‐based microelectronic devices.
High Lithium Ionic Conductivity in the Lithium Halide Hydrates Li3‐n(OHn)Cl (0.83≤n≤2) and Li3‐n(OHn)Br (1≤n≤2) at Ambient Temperatures
Authors: Schwering Georg , Hönnerscheid Andreas , van Wüllen Leo , Jansen Martin 
Published: April 2003

AbstractLithium ionic conductivity and phase transitions in a series of lithium halides hydrates and hydroxides with general formula Li3‐n(OHn)X (0.83≤n≤2; X=Cl,Br) were studied using impedance measurements and 1H and 7Li NMR spectroscopy. All compounds studied in this work crystallize in the antiperovskite structure or are closely related to this structure type. With the exception of LiCl⋅H2O, all compounds with integer lithium content exhibit good lithium ionic conductivity in their high temperature cubic phases above T=33 °C. Lithium doping of samples LiX⋅H2O and Li2(OH)X leads to a suppression of the phase transition into the noncubic phases and the good ionic conductivity is extended down to lower temperatures (T<0 °C). Thus, lithium doping of the lithium halide hydrates provides a promising tool for tailoring the ionic conductivity at ambient temperatures to its optimum value.
OLED and PLED Devices Employing Electrogenerated, Intramolecular Charge‐Transfer Fluorescence
Authors: Goes Marijn , Verhoeven Jan W. , Hofstraat Hans , Brunner Klemens 
Published: April 2003

AbstractThe light generating mechanism of a series of light emitting diodes with electron donor–bridge–acceptor systems (D–b–A) as the emitting species was examined by constructing model diodes based on small organic molecules (OLEDs) as well as on molecularly doped electroactive (poly‐N‐vinylcarbazole, PVK) and insulating (polystyrene, PS) polymers (PLEDs). The direct electrogeneration of an intramolecular charge‐transfer (CT) fluorescence of the donor–bridge–acceptor systems occurred readily in OLED devices with a D–b–A system as the emissive layer. In diodes with PS as the host matrix, hole‐injection and electron‐injection occurred directly in the D–b–A molecules residing close to the anode and the cathode, respectively. In the PVK diodes, hole‐injection occurred primarily into PVK and the positive charge carrier was subsequently trapped on the D–b–A molecule, whereas electron‐injection at the cathode side occurred directly into the D–b–A molecules. Charge‐hopping between neighboring molecules then occurred until a hole and electron resided on the same molecule, which is equivalent to the formation of the CT excited state, and which finally relaxed by intramolecular charge recombination under the emission of CT fluorescence.
On the Temperature–Pressure Free‐Energy Landscape of Proteins
Authors: Ravindra Revanur , Winter Roland 
Published: April 2003

AbstractWe studied the thermodynamic stability of a small monomeric protein, staphylococcal nuclease (Snase), as a function of both temperature and pressure, and expressed it as a 3D free‐energy surface on the p,T‐plane using a second‐order Taylor expansion of the Gibbs free‐energy change ΔG upon unfolding. We took advantage of a series of different techniques (small‐angle Xray scattering, Fourier‐transform infrared spectroscopy, differential thermal analysis, pressure perturbation calorimetry and densitometry) in the evaluation of the conformation of the protein and in evaluating the changes in the thermodynamic parameters upon unfolding, such as the heat capacity, enthalpy, entropy, volume, isothermal compressibility and expansivity. The calculated results of the free‐energy landscape of the protein are in good agreement with experimental data of the p,T‐stability diagram of the protein over a temperature range from 200 to 400 K and at pressures from ambient pressure to 4000 bar. The results demonstrate that combined temperature–pressure‐dependent studies can help delineate the free‐energy landscape of proteins and hence help elucidate which features and thermodynamic parameters are essential in determining the stability of the native conformational state of proteins. The approach presented may also be used for studying other systems with so‐called re‐entrant or Tamman loop‐shaped phase diagrams.
An Ab Initio Study on the Mechanism of the Atmospheric Reaction NH2+O3→H2NO+O2
Authors: Peiró‐García Julio , Nebot‐Gil Ignacio , Merchán Manuela 
Published: April 2003

AbstractThe atmospheric reaction NH2+O3→H2NO+O2 has been investigated theoretically by using MP2, QCISD, QCISD(T), CCSD(T), CASSCF, and CASPT2 methods with various basis sets. At the MP2 level of theory, the hypersurface of the potential energy (HPES) shows a two step reaction mechanism. Therefore, the mechanism proceeds along two transition states (TS1 and TS2), separated by an intermediate designated as Int. However, when the single‐reference higher correlated QCISD and the multiconfigurational CASSCF methodologies have been employed, the minimum structure Int and TS2 are not found on the HPES, which thus confirms a direct reaction mechanism. Single‐reference high correlated and multiconfigurational methods consistently predict the barrier height of the reaction to be within the range of 3.9 to 6.6 kcal mol−1, which is somewhat higher than the experimental value.1 The calculated reaction enthalpy is −67.7 kcal mol−1.
Hydration and Ion Pairing in Aqueous Sodium Oxalate Solutions
Authors: Buchner Richard , Samani Faradj , May Peter M. , Sturm Peter , Hefter Glenn 
Published: April 2003

AbstractDielectric spectra have been measured for aqueous sodium oxalate solutions up to the saturation concentration (0.04≤c [mmol L−1]≤0.25) at 25 °C over the approximate frequency range 0.2≤ν [GHz]≤20. The spectra exhibit a process at about 1 GHz associated with the presence of ion pairs, in addition to the dominant solvent relaxation process at about 18 GHz. Detailed analysis of the solvent dispersion amplitude indicates that the oxalate ion is highly hydrated but that its solvation sheath is “fragile”, decreasing quickly with increasing solute concentration. The NaOx(aq)− ion pair is shown to be of the double‐solvent‐separated (2SIP) type, with an infinite dilution association constant KA=1.04±0.02. Analysis of the ion‐pair relaxation time as a function of solute concentration gave rate constants for the formation (k12=(7.3±0.4)109 L mol−1 s−1) and dissociation (k21=(6.7±0.5)108 s−1) of the ion pair. These values are reasonably close to the diffusion‐controlled values predicted by the Eigen theory, consistent with a 2SIP structure for the ion pair.
Some unmeasured crystal properties
Authors: Raab R. E. 
Published: April 2003

AbstractThe subject of this paper is three macroscopic properties of crystals: Jones birefringence, non‐reciprocal linear birefringence along a cube edge in certain magnetic cubic crystals, and the static magneto‐electric coefficient of magnetic cubic crystals which exhibit this effect. As each of these properties has a particular theoretical interest, and as they remain, as yet, unmeasured, a background account is presented of each, together with the theory, in multipole form, of experiments which would allow the three properties to be measured.
Solid state recrystallization: a promising technique for the growth of semiconductor materials
Authors: Triboulet R. 
Published: April 2003

AbstractExperimental results related to the growth by solid state recrystallization of different semiconductors such as HgCdTe, HgMnTe, CdTe, ZnSe and ZnS are reported and reviewed. The importance of the initial texture and of the deviation from stoichiometry is stressed and the essential role of metal vacancies is emphasized.
YVO4 crystals – puzzles and challenges
Authors: Ryba‐Romanowski W. 
Published: April 2003

AbstractWork on optical properties of undoped and rare‐earth doped YVO4 crystals is briefly reviewed. Fundamental spectroscopic parameters relevant to laser performance of YVO4 containing erbium, thulium and holmium, derived from absorption and emission spectra and from excited state relaxation dynamics, have been presented. Laser performance of YVO4:Er has been reported and laser potential of YVO4 doped with thulium and holmium has been assessed. Anomalous phenomenon of up‐conversion of IR radiation into red emission in YVO4:Yb,Ho and puzzling anti Stokes emission in nominally undoped YVO4 have been discussed.
Advances in modeling of wide‐bandgap bulk crystal growth
Authors: Bogdanov M. V. , Demina S. E. , Karpov S. Yu. , Kulik A. V. , Ramm M. S. , Makarov Yu. N. 
Published: April 2003

AbstractWe review key aspects of sublimation growth of wide‐bandgap semiconductors like SiC, AlN and GaN, and show how modeling can help to solve a number of practical problems. As the temperature distribution in the growth chamber is the most critical factor in the sublimation technology, we discuss in detail specific features of heat transfer with the focus on the porous materials normally involved in the growth system: powder source, thermal insulation, and graphite. The species transport is simulated using advanced models accounting for a multicomponent vapor and the kinetics of chemical interaction of nitrogen‐containing species with the surface of group‐III nitrides. The effect of growth conditions on parasitic phase formation is analyzed. To optimize the growth system design and operating conditions, we suggest an inverse‐problem approach instead of commonly used trial‐and‐error methods. This simulation procedure has proved quite efficient for getting design solutions, which could hardly be found by conventional straightforward methods. In particular, we demonstrate the effectiveness of the inverse modeling for finding the growth conditions, which provide crystals of desired shapes. A special analysis is made to establish a correlation between the growth conditions and defect distribution in the grown crystal, with the focus on thermoelastic stress produced by temperature gradients. The high‐temperature dynamics of gliding dislocations and consequent plastic stress relaxation in the material is examined. The prospective of global modeling of wide‐bandgap crystal growth by sublimation and still open questions are discussed.
Scanning probe microscopy and computer simulations: Complementary techniques for nanostructured materials and thin films
Authors: Richter A. , Smith R. 
Published: April 2003

AbstractIt is demonstrated how scanning force microscopy in combination with recent simulation techniques and computer power can be used in a complementary way in the analysis and explanation of thin film growth and nanoindentation on crystal surfaces. Simulation techniques such as Monte Carlo models and molecular dynamic models are applied for thin film growth and nanoindentation. The formation of the first molecular layers in the growth of C60 films on silicon can be modelled by classical molecular dynamics to show the different bonding behaviour between C60 molecules, which results in hexagonal and cubic structures with stacking faults within the C60 film. Ab initio calculations of C60 bonding sites to the silicon surface classify bond types by the length and the energy of the C‐Si bonds. Strong binding energies between the C60 molecule and the Si atoms are obtained to fix the C60 molecule at a definite position. Different growth modes such as island and layer growth of C60 films can be studied by Monte Carlo simulations, including diffusion of atoms within the cluster and cluster diffusion over the surface itself. A brief experimental view of the nanoindentation process is given in combination with molecular dynamics simulations for the penetration of the tip into a C60 surface. The crystal symmetry is reflected during the plastic deformation in the pile‐up structure around the indentation hole in relation to the orientation of the indenter and the crystal surface. As an example of these investigations results are given for nanoindentation into the Fe{110} single crystal surface.
Mixtures of organic macrocycles for applications in solar cell devices
Authors: Boguta A. , Wróbel D. , Hoffmann T. J. , Mazurkiewicz P. 
Published: April 2003

AbstractIn this paper we present spectroscopic and photoelectric studies of two families of macrocycles and their mixtures: phthalocyanines and naphthalocyanines complexed with various ions. The dyes are characterized by significant light absorption and each dye absorbs in a different spectral region and covers only a part of the solar light spectrum. The use of the dyes mixture extends the light absorption region and can lead to the enhancement of photovoltaic effects. The spectroscopic properties are studied to establish the radiative and non–radiative deactivation pathways of the dye excited states as processes competitive to charge separation. As it is shown, the excitation energy transfer improve the efficiency of light energy to electric energy conversion. The dynamics of the electromagnetic field in the phthalocyanine–naphthalocyanine–solvent system as a multicomponent body in the sense of extended phenomenological electrodynamics is also presented. Lagrange–Hamilton formalism can be used in the investigation of the local electromagnetic field in the dyes–solvent mixture. The presented results seem to be essential in the determination of the conditions required for the enhancement of the photoeffects in the photoelectrochemical cell based on the organic materials.
Rb3Lu(PO4)2:Ce and Cs3Lu(PO4)2:Ce – new promising scintillator materials
Authors: Wisniewski D. , Wojtowicz A. J. , Drozdowski W. , Farmer J. M. , Boatner L. A. 
Published: April 2003

AbstractCs3Lu(PO4)2:Ce and Rb3Lu(PO4)2:Ce single crystals have been studied under gamma‐, x‐ray and UV excitation. For all types of excitation the luminescence of these materials is dominated by a broad Ceemission band positioned at the UV/visible light boundary. Highly efficient and relatively fast scintillation of both materials identify them as promising scintillators.
Growth and TEM and HREM characterisation of TiC crystals grown from high‐temperature solutions
Authors: Strzeciwilk D. , Wokulski Z. , Tkacz P. 
Published: April 2003

AbstractThe results of TiC crystals and Ni microstructure studies by means of transmission electron microscope are presented. It was shown that Ni may be used as high temperature solvent for obtaining TiC crystals. This paper reports the results of morphology and growth of TiC crystals. The obtained TiC crystals with application of Ni as high temperature solvent were mainly of {001} cubic form, although irregular forms were also observed. Detailed TEM and HREM studies have shown that dislocations are formed in the vicinity of incoherent TiC precipitates in Ni matrices.
Preparation of semi‐insulating CdTe doped with group IV elements by post growth annealing
Authors: Turkevych I. , Grill R. , Franc J. , Höschl P. , Belas E. , Moravec P. , Fiederle M. , Benz K. W. 
Published: April 2003

AbstractThermodynamic conditions for post‐growth annealing to prepare near stoichiometric semi‐insulating CdTe are studied for undoped, and Sn and Ge‐doped single crystals. The main aim of the annealing procedure was to obtain high resistive material with the minimal concentration of native and foreign defects. The high temperature (200 – 1000 °C) in‐situ conductivity σ and Hall effect measurements were used to control the native defect density and to determine the Cd pressure pCd at which shallow defects are compensated. It is shown that contrary to the undoped samples in which the change of the type of conductivity by variations of pCd is easy, the Sn‐ and Ge‐doped samples exhibit a much more stable behavior due to the Sn (Ge) selfcompensation. It was found that: the temperatures near 500 °C is optimum for the real‐time annealing of bulk samples, the chemical diffusion is sufficiently fast at these temperatures while the uncontrolled change of defect density distribution during the subsequent cooling process is minimized. The time‐dependent charge measurement technique was used to characterize the room‐temperature specific resistivity distribution in the as‐grown crystals, which indirectly controls the dynamic of solidification process. This allows us to consider the specific resistivity distribution along the growth direction of each crystal in terms of superposition of segregation and self‐compensation phenomena.
Application of tungsten films for substrate masking in liquid phase epitaxial lateral overgrowth of GaAs
Authors: Dobosz D. , Zytkiewicz Z. R. , Piotrowski T.T. , Kaminska E. , Papis E. , Piotrowska A. 
Published: April 2003

AbstractLiquid phase epitaxial lateral overgrowth of GaAs layers on GaAs substrates masked by tungsten films was studied. We show that at our growth conditions perfect growth selectivity was obtained, so the layers started growing from the openings cut in the mask only. However, serious damage of the mask during epitaxial growth was observed. As this deteriorates crystallographic quality of the layers a procedure was elaborated to eliminate degradation of the tungsten film by the melt. In particular, reduction of growth temperature and deposition of Au/Zn wetting layers between tungsten film and the GaAs substrate were found important to avoid degradation of the mask and for successful lateral growth of the layers. Tungsten masked GaAs substrates were then used for lateral overgrowth of GaAs by liquid phase electroepitaxy. Preliminary results are presented showing that application of electrically conductive tungsten mask, which allows a direct DC current flow from the melt to the substrate, results in much wider and thinner electroepitaxial layers than those grown on the substrates coated by insulating film.
Stress‐induced structural changes in thin InAs layers grown on GaAs substrate
Authors: Bak‐Misiuk J. , Shalimov A. , Kaniewski J. , Misiuk A. , Dynowska E. , Reginski K. , Trela J. , Przesławski T. , Hartwig J. 
Published: April 2003

AbstractEffect of high temperature‐high pressure treatment on strain state of the lattice mismatched InAs layers grown on the GaAs substrate was investigated by means of X‐ray diffraction methods. The InAs layers were grown on (100) oriented GaAs by molecular beam epitaxy. Measurements of the rocking curve width and lattice parameters were carried out using high resolution diffractometer. Annealing of the InAs/GaAs structure performed at high pressure changes its strain state and defect structure. Especially, annealing at the growth temperature at high pressure was found to be effective in improvement of the structural perfection of the layer. It means that thin InAs layers having comparatively low dislocation density can be produced by high temperature ‐ high pressure procedure. The relative changes of threading dislocation density were sensitive to the temperature of the treatment, however they were independent of the primary defect structure of the samples.
Deformation of decagonal Al‐Cu‐Co single quasicrystals
Authors: Bogdanowicz W. 
Published: April 2003

AbstractDeformation process of decagonal single quasicrystals of Al‐Cu‐Co alloy was studied by X‐ray topography and optical microscopy. The deformation was performed at elevated temperature (550°C) not higher than the temperature of disordering transformation of clusters inside anti‐phase domains (600°C). It was found that at a deformation of about 3–5% glide occurs only in the direction of ten‐fold symmetry axis in which the boundaries of anti‐phase domains are arranged. At a deformation of about 7–9% the samples cracked.
Study of surface morphology of electrochemically etched n‐Si (111) electrodes at different anodic potentials
Authors: Jakubowicz J. 
Published: April 2003

AbstractChanges of n‐Si (111) silicon surface morphology after anodisation at different voltage conditions in dilute NH4F solutions were studied by AFM technique. The electrochemical etching was done with respect to current‐voltage (I‐V) characteristics. The Si surface was investigated at increasing and constant voltage conditions. The porous silicon was formed at potentials slightly anodic from the rest potential (from ‐0.6 V to 0.02 V). On the other hand silicon oxide formation and electropolishing occurs at higher anodic potentials. The sustained current oscillations take place in the Si electrode, at 6 V potential in dilute NH4F solution. The nature of oscillations was attributed to cyclic silicon oxide formation and its dissolution. The surface undergoes from smooth (before oscillation peak) to rough (little before top of the peak) during oscillation peak, and finally transforms to smooth at the bottom of the peak. It was confirmed by the roughness parameter.
Influence of nanocrystalization on magnetoelastic Villari effect in Fe73.5Nb3Cu1Si13.5B9 alloy
Authors: Szewczyk R. , Bienkowski A. , Kolano R. 
Published: April 2003

AbstractThe results of an investigation of the influence of thermal annealing on the magnetoelastic properties of Fe73.5Nb3Cu1Si13.5B9 soft magnetic alloy in both amorphous and nanocrystalline state are presented. A new method developed was used to apply uniform compressive stresses to the investigated ring core made of the alloy. The compressive stresses produced by external mechanical forces were applied perpendicularly to the direction of the magnetizing field. Due to the uniform distribution of stresses in the core brittle nanocrystalline alloys may be tested for stresses up to 10 MPa. The results revealed, that process of nanocrystallisation causes significant increase in the stress sensitivity of the Fe73.5Nb3Cu1Si13.5B9 alloy. Moreover the influence of stresses caused by external forces is more significant at relatively low values of the magnetizing field suggesting that these nanocrystalline soft magnetic materials are stress sensitive in the range of technical operation of inductive components based on such materials.