bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nuclear field effect on the spin dynamics of electron localized on a donor in a single quantum well
Authors: Testelin C. , Aubry E. , Bernardot F. , Chamarro M. , Karczewski G. 
Published: February 2008

AbstractWe use photoinduced Faraday rotation (PFR) in presence of an applied magnetic field to study the spin dynamics of localized electrons. The sample is a CdTe/CdMgTe quantum well (QW) of width 80 Å containing a layer of iodine donors at its center, with concentration 1011 cm–2. The spin polarization of donor‐bound electrons is built via the optical polarization of donor‐bound excitons, their hole spin relaxation, and their recombination. In a transverse (in‐plane) magnetic field, PFR shows damped Larmor oscillations from which we deduce a 18 ns electron‐spin decoherence time, and a transverse Landé factor of 1.29. In addition, for oblique optical incidence the electron‐nuclei hyperfine interaction builds a nuclear spin polarization in presence of polarized electrons. This leads to the construction of an effective magnetic field, the Overhauser field, acting on the electronic spins. The Larmor frequency is then different for σ+ or σ– polarizations of the exciting light. The dependence of the phenomenon on the optical incidence allows the determination of the maximal Overhauser field, which is about 10 mT, at least two orders of magnitude weaker than for III‐V semiconductors. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Anomalous resonant nonlinear absorption of excitons in CdSe/ZnS quantum dots
Authors: Dneprovskii V. , Kabanin D. , Lyaskovskii V. , Wumaier T. , Zhukov E. 
Published: February 2008

AbstractWe have explained the observed anomalous dependence of colloidal CdSe/ZnS quantum dots' (QDs) absorption upon the intensity of input picosecond laser pulses in the case of one‐photon resonant excitation of exciton 1S3/2(h) – 1S (e) transition – the linear absorption at low intensity is replaced by nonlinear decreasing and then increasing of absorption (!) at high intensities – by saturation effect (state filling) of two‐level system with variable lifetime of the excited state (variable saturation intensity). The lifetime decreases at high excitation due to nonradiative Auger recombination. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Nonlinear absorption and refraction of CdSe/ZnS quantum dots at two‐photon resonant excitation of excitons
Authors: Dneprovskii V. , Kabanin D. , Lyaskovskii V. , Santalov A. , Wumaier T. , Dang Thai Giang , Zhukov E. 
Published: February 2008

AbstractThe observed nonlinear absorption, optical limiting and nonlinear refraction of colloidal CdSe/ZnS quantum dots in the case of two‐photon resonant excitation of 1S3/2(h) – 1S (e) exciton transition by powerful picosecond laser pulses have been explained by two‐photon absorption and self‐defocusing effect. The results of experiments have allowed to separate self‐defocusing effects arising due to the change of nonlinear refractive index of bound electrons and nonlinear refraction from two‐photon generated carriers. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effect of matrix parameters on mesoporous matrix based quantum computation
Authors: Hodgson T. E. , Bertino M. F. , Leventis N. , D'Amico I. 
Published: February 2008

AbstractWe present a solid state implementation of quantum computation, which improves previously proposed optically driven schemes. Our proposal is based on vertical arrays of quantum dots embedded in a mesoporous material which can be fabricated with present technology. We study the feasibility of performing quantum computation with different mesoporous matrices.We analyse which matrix materials ensure that each individual stack of quantum dots can be considered isolated from the rest of the ensemble‐a key requirement of our scheme. This requirement is satisfied for all matrix materials for feasible structure parameters and GaN/AlN based quantum dots. We also show that one dimensional ensembles substantially improve performances, even of CdSe/CdS based quantum dots. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Strong excitonic mixing effect in asymmetric double quantum wells: On the optimization of electroabsorption modulators
Authors: Kim Dong Kwon , Citrin D. S. 
Published: February 2008

AbstractWe investigate the mixing of excitons originating in different subband pairs in asymmetric double quantum wells (ADQWs) in a range of electric field where the two lowest exciton states anticross. This excitonic mixing is mainly attributed to the Coulomb interactions between subbands and the valence‐subband nonparabolicity. Results show that excluding the excitonic mixing effect results in significant error in both the energies and the oscillator strengths of the excitons in an ADQW with thick barrier (3 nm). Even in an ADQW with a fairly thin barrier (1.2 nm), the error in the oscillator strengths can be substantial, although the errors in the computed energies may be tolerable. We find that including the mixing of excitons is indispensable in optimizing the structures of the asymmetric double quantum well electroabsorption modulators. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electrical and optical charging of CdTe quantum dots
Authors: Kłopotowski Ł. , Kudelski A. , Wojnar P. , Krebs O. , Voisin P. , Karczewski G. , Wojtowicz T. 
Published: February 2008

AbstractWe study two charging mechanisms of CdTe self assembled quantum dots embedded in a field effect structure: A standard electrical injection of carriers from the back contact resulting from an application of a gate voltage and a novel all‐optical effect. The optical charging results from a reduction of the built in electric field by an above barrier illumination, which enables the tunneling of carriers from the back contact. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Near‐field control of the light emission properties of a symmetric semiconductor quantum dot
Authors: Pistone G. , Savasta S. , Di Stefano O. , Martino G. , Girlanda R. , Portolan S. 
Published: February 2008

AbstractWe study the carrier capture and distribution among the available energy levels of a symmetric semiconductor quantum dot under continuous‐wave optical excitation resonant with the barrier energy levels. We find that at low temperature all the dot level‐occupations but one decrease monotonically with energy. The uncovered exception, corresponding to the second (dark) energy level, displays a steady‐state carrier density exceeding that of the lowest level more than a factor two. The root cause is not radiative recombination before relaxation to lower energy levels, but at the opposite, carrier trapping due to the symmetry‐induced suppression of radiative recombination. We show that spatially resolved photoluminescence spectroscopy can detect the evanescent waves generated by dark states occupations, allowing the observation of such effects. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Luminescence and energy structure of ultrathin InAs/AlAs quantum wells
Authors: Shamirzaev T. S. , Gilinsky A. M. , Kalagin A. K. , Zhuravlev K. S. 
Published: February 2008

AbstractThe energy spectrum of thin InAs/AlAs quantum wells (QWs) has been studied by photoluminescence (PL). It has been found that the PL spectra of the QWs consist of intense lines related to a no‐phonon excitonic transition accompanied with its phonon replicas. The band alignment in the QWs with the lowest conduction band states belonging to the indirect minimum is shown to be of type I. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Control of the concentration of protons intercalated into tungsten oxide thin films during deposition
Authors: Yamada Y. , Tajima K. , Okada M. , Bao S. , Tazawa M. , Yoshimura K. , Roos A. 
Published: February 2008

AbstractTungsten oxide thin films with protons intercalated during deposition (Hx WO3) were prepared using reactive direct‐current magnetron sputtering in a gas mixture of argon, oxy‐gen, and hydrogen. The as‐deposited films were tungsten bronze. The concentration of intercalated protons, given by the x ‐values in Hx WO3, was evaluated by electrochemically ejecting protons from the films. The x ‐value was proportional to the hydrogen flow ratio at the deposition. The dispersion of the extinction coefficient (κ) of the films was estimated by analyzing the experimental spectra measured with spectroscopic ellipsometry using the model composed of a homogeneous tungsten bronze layer with an additional surface roughness layer. As a result of this analysis, the κ ‐value increases strongly with intercalated protons, and a linear dependence existed between the x ‐value and κ ‐value. Therefore, it is possible to evaluate the x ‐value of the Hx WO3 films using this dependence without ejecting protons. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Spectroscopic ellipsometry of silicon‐containing diamond‐like carbon (DLC‐Si) films
Authors: Kato Naohiko , Mori Hiroyuki , Takahashi Naoko 
Published: February 2008

AbstractTo clarify optical properties of DLC‐Si film, we have studied the change in optical constants of the DLC‐Si films as a function of the Si content using spectroscopic ellipsometry. Using the 4 layered structure model (substrate/interface/film/surface roughness/adsorbed water/air), the thickness of each layer and the parameters of the Tauc‐Lorentz oscillator of the film were estimated. The calculated spectra agreed well with the measured one using the layered model with adsorbed water on the DLC‐Si films, compared to the model without water. The thickness of the adsorbed water was in the range from 1nm to 4nm on the DLC‐Si films. However, there was no adsorbed water on the DLC film. This fact is consistent with the larger content of silanol (Si‐OH) measured by the derivatization‐XPS of the DLC‐Si films, compared to that of the DLC film. We have clarified that the refractive index increased at the broad range of 200‐850 nm, the extinction coefficient at the broad range of 200‐1700 nm decreased with an increase in the Si content of the DLC‐Si films. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Spectroscopic ellipsometry analysis of multilayered TiO2‐Ag thin films for photochromic application
Authors: Miao L. , Jiang T. , Tanemura S. , Tanemura M. , Nabatova‐Gabain N. , Xu G. 
Published: February 2008

AbstractBy altering the surrounding media of metal particles, the wavelength of surface plasma resonance can be tailored, which offers the potential for utilizing of plasma resonance related phenomenon, such as photochromism. Both sandwiched (TiO2/Ag/TiO2) and overcoated (TiO2/Ag) films with different thicknesses were deposited on quartz substrate by rf helicon magnetron sputtering method. The structure of multilayered TiO2‐Ag films and the concentration of loaded metal Ag in each layer were determined by spectroscopic ellipsometry in high accuracy. The spectral dependent dielectric functions of each layer were obtained, which exhibited typical semiconductor TiO2, metal Ag and mixture TiO2‐Ag behaviors, respectively. The surface plasma resonance peak was observed for several extremely thin mixture layers. The apparent redshift of SPR peak from 700 nm to 780 nm was happened with increasing of Ag amount from 35% to 50%. The broadening of SPR peak was found for layer 3 in sample 1 with low concentration Ag embedded in TiO2 media. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical quantities of rough films calculated by Rayleigh‐Rice theory
Authors: Franta Daniel , Ohlídal Ivan , Necas David 
Published: February 2008

AbstractExperimental ellipsometric and spectroscopic data of a randomly rough silicon substrate are treated using several theoretical approaches. It is shown that the effective medium approximation and scalar diffraction theory are unsuitable approaches for treating the experimental data of rough surfaces containing spatial frequencies comparable with the wavelength of incident light. Using the Rayleigh‐Rice theory one can obtain an excellent fit of the experimental data and very close agreement between the values of the statistical parameters determined using the optical method and atomic force microscopy. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical characterization of phase changing Ge2Sb2Te5 chalcogenide films
Authors: Franta Daniel , Hrdlicka Martin , Necas David , Frumar Miloslav , Ohlídal Ivan , Pavli šta Martin 
Published: February 2008

AbstractThe variable angle spectroscopic ellipsometry and spectroscopic reflectometry is used for the optical characterization of the as‐deposited and annealed Ge2Sb2Te5 (GST) films. The dispersion model of the GST films is based on the parameterization of the density of electronic states. As a consequence of annealing, roughness of the upper boundaries of the GST films originates. This annealing also causes the evident redistribution of the density of electronic states from the higher energies to lower energies. The roughening and redistribution of the electrons are explained by means of the phase change of the GST films from amorphous to polycrystalline structure. This phase change is accompanied by changing the conductivity of the films that was proved by introducing the terms of the free carriers in the dispersion model of the GST films. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Spectroscopic ellipsometry and reflectometry of statistically rough surfaces exhibiting wide intervals of spatial frequencies
Authors: Ohlídal Ivan , Necas David , Franta Daniel 
Published: February 2008

AbstractTwo optical methods for the optical characterization of the statistically rough surfaces exhibiting wide intervals of spatial frequencies are presented. These methods employ the combination of variable angle spectroscopic ellipsometry and near‐normal spectroscopic reflectometry. The first method is based on combining the scalar diffraction theory and effective medium theory while the second method combines the scalar diffraction theory with Rayleigh‐Rice theory.Both the methods are applied to the optical characterization of statistically rough GaAs surfaces prepared by thermal oxidation. It is shown that both the methods can be utilized for characterization of these surfaces in a reasonable way, however, the latter is more suitable for this purpose. The results of the optical characterization of the selected rough GaAs surface are supported by those obtained using atomic force microscopy. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Spectroscopic ellipsometric study of Ge nanocrystals embedded in SiO2 using parametric models
Authors: Basa P. , Petrik P. , Fried M. , Dâna A. , Aydinli A. , Foss S. , Finstad T. G. 
Published: February 2008

AbstractGe‐rich SiO2 layers on top of Si substrates were deposited using plasma enhanced chemical vapour deposition. Ge nanocrystals embedded in the SiO2 layers were formed by high temperature annealing. The samples were measured and evaluated by spectroscopic ellipsometry. Effective medium theory (EMT) and parametric semiconductor models have been used to model the dielectric function of the layers. Systematic dependences of the layer thickness and the oscillator parameters have been found on the annealing temperature (nanocrystal size). (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical properties of NiCrOx thin films
Authors: Dahmouchène Nora , Voué Michel , Stehlé Jean‐Louis , Defranoux Christophe , Nouvellon Corinne , De Coninck Joel 
Published: February 2008

AbstractThe optical properties of thin NiCrOx layers were investigated by spectroscopic ellipsometry (SE). The layers were coated on float glass by magnetron sputtering at different oxygen partial pressures (20% to 30% oxygen in the sputtering gas) and the influence of the degree of oxidation was considered in details. The optical constants of the films n and k, in the visible to near infrared spectral range (0.35 to 1.7 mm), appear to be extremely sensitive to their chemical composition. Complementary studies were carried out using Fourier transform infrared ellipsometry (FTIR‐SE) to determine the optical conductivity of the films and compare it with four‐points‐probe measurements. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An automatic imaging spectroscopic ellipsometer for characterization of nano‐film pattern on solid substrate
Authors: Meng Y. H. , Chen Y. Y. , Qi C. , Liu L. , Jin G. 
Published: February 2008

AbstractIn order to characterize the physical and spatial properties of nano‐film pattern on solid substrates, an automatic imaging spectroscopic ellipsometer (ISE) based on a polarizer ‐ compensator ‐ specimen ‐ analyzer configuration in the visible region is presented. It can provide the spectroscopic ellipsometric parameters ψ (x, y, λ) and Δ (x, y, λ) of a large area specimen with a lateral resolution in the order of some microns. A SiO2 stepped layers pattern is used to demonstrate the function of the ISE which shows potential application in thin film devices such as high‐throughput bio‐chips. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
QSAR Models for Prediction of Glycogen Synthase Kinase‐3β Inhibitory Activity of Indirubin Derivatives
Authors: Lather Viney , Kristam Rajendra , Saini Jagmohan Singh , Kristam Rajendra , Karthikeyan Narasingapuram Arumugam , Balaji Vitukudi Narayana 
Published: February 2008

AbstractGlycogen Synthase (GS) Kinase‐3 (GSK‐3), a serine/threonine kinase, isolated and purified as an enzyme capable of phosphorylating and inactivating the enzyme GS is a fascinating enzyme with diverse biological actions in intracellular signaling pathways. A large body of evidence supports speculation that pharmacological inhibitors of GSK‐3 could be used to treat several disorders including Alzheimer's disease and other neurodegenerative diseases, bipolar affective disorder, diabetes, various types of cancer, and diseases caused by unicellular parasites that express GSK‐3 homologues. In the present work, we have carried out a Quantitative Structure–Activity Relationship (QSAR) study on indirubin derivatives reported as potent GSK‐3β inhibitors using molecular descriptors calculated by CODESSA and Molconn‐Z. Also a novel Three‐Dimensional QSAR (3D‐QSAR) study based on the principle of the alignment of pharmacophoric features by PHASE module of Schrödinger suite has been carried out on the same set of inhibitors. Statistically significant 2‐D (R2=0.93) and 3‐D (R2=0.97) QSAR models were generated using 36 molecules in the training set. The predictive ability of both models was determined using a randomly chosen test set of eight molecules which gave predictive correlation coefficients ($\rm{ R_{{\rm{pred}}}^{\rm{2}} }$) of 0.6 and 0.91, respectively for 2‐D and 3‐D models, indicating good predictive power. The cocrystallographic data of GSK‐3β with indirubin‐3′‐monoxime ligand allowed us to compare the PHASE pharmacophore model with experimental intermolecular interactions. The results of PHASE pharmacophore hypothesis AADDRR correspond very closely to the interactions recorded in the active site of the ligand bound complex. This relation between the crystallographic data and pharmacophore hypothesis allowed us to confirm the preferential binding mode of indirubins inside the active site. These studies showed that 3D‐QSAR model is a better predictive model for the indirubins compared to 2D‐QSAR model.
Comment on the connected‐moments polynomial approach
Authors: Marmorino M. G. 
Published: February 2008

AbstractBartashevich has recently proposed two new methods for approximating eigenvalues of a Hamiltonian. The first method uses Hamiltonian moments generated from a trial function and his second method is a generalization of local energy methods. We show that the first method is equivalent to a variational one, a matrix eigenvalue problem using a Lanzcos subspace. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008
Simultaneous quantitative determination of amphetamines, ketamine, opiates and metabolites in human hair by gas chromatography/mass spectrometry
Authors: Wu Ya‐Hsueh , Lin Keh‐Liang , Chen Su‐Chin , Chang Yan‐Zin 
Published: February 2008

AbstractA gas chromatography/mass spectrometry (GC/MS) method was developed and validated for the determination of common drugs of abuse in Asia. The method was able to simultaneously quantify amphetamines (amphetamine; AP, methamphetamine; MA, methylenedioxy amphetamine; MDA, methylenedioxymeth mphetamine; MDMA, methylenedioxy ethylamphetamine; MDEA), ketamine (ketamine; K, norketamine; NK), and opiates (morphine; MOR, codeine; COD, 6‐acetylmorphine; 6‐AM) in human hair. Hair samples (25 mg) were washed, cut, and incubated overnight at 25°C in methanol/trifluoroacetic acid (methanol/TFA). The samples were extracted by solid‐phase extraction (SPE), derivatized using heptafluorobutyric acid anhydride (HFBA) at 70°C for 30 min, and the derivatives were analyzed by electron ionization (EI) GC/MS in selected ion monitoring mode. Confirmation was accomplished by comparing retention times and the relative abundances of selected ions with those of standards. Deuterated analogs of the analytes were used as internal standards for quantification. Calibration curves for ten analytes were established in the concentration range 0.1–10 ng/mg with high correlation coefficients (r2 > 0.999). The intra‐day and inter‐day precisions were within 12.1% and 15.8%, respectively. The intra‐day and inter‐day accuracies were between −8.7% and 10.7%, and between −5.9% and 13.8%, respectively. The limit of detection (LOD) and limit of quantification (LOQ) obtained were 0.03 and 0.05 ng/mg for AP, MA, MDA, MDMA and MDEA; 0.05 and 0.08 ng/mg for K, NK, MOR and COD; and 0.08 and 0.1 ng/mg for 6‐AM. The recoveries were above 88.6% for all the compounds, except K and NK which were in the range of 71.7–72.7%. Eight hair samples from known polydrug abusers were examined by this method. These results show that the method is suitable for broad‐spectrum drug testing in a single hair specimen. Copyright © 2008 John Wiley & Sons, Ltd.
Structural Study of Titanium Oxide Films Synthesized by Ion Beam‐Assisted Deposition
Authors: Wang Gonghua , Brewer Joseph R. , Namavar Fereydoon , Sabirianov Renat F. , Haider Hani , Garvin Kevin L. , Cheung Chin Li 
Published: February 2008

AbstractThe application of titanium dioxide (TiO2) films as surgical implant coatings for antibiotic attachment depends crucially on their available surface area and thus their surface morphology and crystallinity. Here, we report our fabrication of high Wenzel ratio TiO2 films targeted to increase the film surface area using the ion beam‐assisted deposition (IBAD) technique at high‐deposition temperatures (∼610 °C). The modulation of the films' surface morphology was accomplished by varying the chemical identity of the concurrent ion beams bombarded on the films during the e‐beam evaporation process. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) were employed to investigate the surface morphology of the as‐deposited films. X‐ray diffractometry (XRD) revealed that these nanocrystalline films primarily consist of anatase phase TiO2. Wenzel ratio, the ratio of the actual surface area to the projected area, of IBAD films prepared with argon, oxygen, and nitrogen ion beams was measured to be 1.52, 1.31 and 1.49, respectively. The effect of the differences in chemical reactivity and ion size of these three type ion beams are discussed to explain the present results. SCANNING 30: 000–000, 2008. © 2008 Wiley Periodicals, Inc.