Showing papers in "Physica B-condensed Matter in 2006"
TL;DR: In this paper, the physical causes of non-radiative recombination are analyzed and the increase in the density of the impurities responsible for the mid-gap levels to the point of forming bands is suggested as the means of suppressing the recombination.
Abstract: There is a practical interest in developing semiconductors with levels situated within their band gap while preventing the non-radiative recombination that these levels promote. In this paper, the physical causes of this non-radiative recombination are analyzed and the increase in the density of the impurities responsible for the mid-gap levels to the point of forming bands is suggested as the means of suppressing the recombination. Simple models supporting this recommendation and helping in its quantification are presented.
286 citations
TL;DR: In this article, the elastic, electronic and lattice dynamical properties of chalcogenides (CdS, CdSe, and CdTe) were investigated based on norm-conserving pseudopotentials and density functional theory.
Abstract: Ab initio calculations, based on norm-conserving pseudopotentials and density functional theory, have been performed to investigate elastic, electronic and lattice dynamical properties of chalcogenides (CdS, CdSe, and CdTe). The calculated lattice parameters, elastic constants, band structures, and phonon dispersions are in good agreement with available experimental and theoretical results. We also presented the pressure-dependence of elastic constants and the pressure-dependence of band gaps.
244 citations
TL;DR: In this article, the authors analyzed the ionic conductivity of the chitosan-NH 4 CF 3 SO 3 system over a wide range of frequency and at temperatures between 298 and 313 k. The temperature dependent conductivity data obeys Arrhenius relationship.
Abstract: Ionic conductivity for the chitosan-NH 4 CF 3 SO 3 system was conducted over a wide range of frequency and at temperatures between 298 and 313 K. Dielectric data were analyzed using complex permittivity e * and complex electrical modulus M * for the sample with the highest ionic conductivity at various temperatures. The temperature-dependent conductivity data obeys Arrhenius relationship. Jonschers universal power law was used to analyze AC conductivity of the sample. Hopping frequency was determined and activation energy of hopping is almost equal to the activation energy of conduction. The AC conductivity master curve was obtained for the highest conducting sample when scaled vertically by σ DC and horizontally by ω P .
242 citations
TL;DR: A powder diffractometer aiming for high angular, and thus high reciprocal space, resolution is being constructed within the Neutron Beam Instrumentation Project at the upcoming Australian NEutron Source OPAL, near Sydney as discussed by the authors.
Abstract: A new powder diffractometer aiming for high angular, and thus high reciprocal space, resolution is being constructed within the Neutron Beam Instrumentation Project at the upcoming Australian Neutron Source OPAL, near Sydney. The neutron flux at the sample can be expected to be up to 10 7 n/cm 2 /s. With an array of 128 position sensitive detectors, each equipped with a 30 cm high Soller collimator of 5 arc min acceptance this instrument will have one of the highest performances of its kind. In addition to classical applications in powder diffraction, the quasi two-dimensional detector will be used for rapid texture measurements, where high separation of peaks is necessary. Even single crystal reciprocal space mapping is envisaged. The article compiles an overview of the design, status of the project and potential research activities.
233 citations
TL;DR: The Wombat powder diffractometer as discussed by the authors was designed for experiments requiring rapid real-time acquisition (time-resolved environmental or kinetics experiments) or very good signal to noise (experiments with difficult sample environments or small sample volumes).
Abstract: The Wombat powder diffractometer will be located on the TG1 thermal guide at the OPAL reactor. A variable vertically focusing monochromator will provide a flux of up to ≈108 ns−1 cm−2 at the sample position. A compact curved 2D position sensitive detector will allow simultaneous acquisition of 120 ° in 2θ, with ≈106 s−1 count rate capability and time resolution down to the microsecond level. Wombat is designed for experiments requiring rapid real time acquisition (time-resolved environmental or kinetics experiments) or very good signal to noise (experiments with difficult sample environments or small sample volumes).
231 citations
TL;DR: The Spallation Neutron Source (SNS) as mentioned in this paper is a state-of-the-art particle accelerator that produces the most intense beams of pulsed neutrons in the world.
Abstract: When completed in 2006, the Spallation Neutron Source (SNS) will use an accelerator to produce the most intense beams of pulsed neutrons in the world. This unique facility is being built by a collaboration of six US Department of Energy laboratories and will serve a diverse community of users drawn from academia, industry, and government labs. The project continues on schedule and within budget, with commissioning and installation of all systems going well. Installation of 14 state-of-the-art instruments is under way, and design work is being completed for several others. These new instruments will enable inelastic and elastic-scattering measurements across a broad range of science such as condensed-matter physics, chemistry, engineering materials, biology, and beyond. Neutron Science at SNS will be complemented by research opportunities at several other facilities under way at Oak Ridge National Laboratory.
180 citations
TL;DR: In this article, the electronic structures of ZnO-based dilute magnetic semiconductors within the self-interaction-corrected local density approximation were calculated and compared with those calculated within the standard LDA.
Abstract: We calculate the electronic structures of ZnO-based dilute magnetic semiconductors within the self-interaction-corrected local density approximation. The results are compared with those calculated within the standard local density approximation. We find the differences in the band gap energy, the energetic position of the Zn 3d bands, and the description of the transition-metal d bands.
167 citations
TL;DR: A small-angle neutron scattering instrument (Quokka) is being built as part of the initial instrument suite for the 20MW Australian Research Reactor, OPAL.
Abstract: A small-angle neutron scattering instrument (Quokka) is being built as part of the initial instrument suite for the 20 MW Australian Research Reactor, OPAL. The 40 m long instrument will be located at the end of a curved supermirror neutron guide and will receive neutrons from a large liquid-D2 cold source. The instrument will have incident beam polarisation and focusing optics using MgF2 lenses and gravity-correcting prisms in the collimation system. The secondary flight path includes a 1 m2 area detector with high-speed data acquisition electronics with provision for the inclusion of polarisation analysis at a later date.
152 citations
TL;DR: In this paper, the Materials Science Diffractometer STRESS-SPEC at FRM-II is designed to be equally applied to texture or residual stress analysis by virtue of its flexible configuration and the high neutron flux at the sample position.
Abstract: In response to the development of new materials and the application of materials and components in new technologies the direct measurement, calculation and evaluation of textures and residual stresses has gained worldwide significance in recent years. In order to cater for the development of these analytical techniques the Materials Science Diffractometer STRESS-SPEC at FRM-II is designed to be equally applied to texture or residual stress analysis by virtue of its flexible configuration and the high neutron flux at the sample position. The instrument is now available for routine operation and here we present details of first experiments and instrument performance.
122 citations
TL;DR: In this article, the electronic structure and formation energies of cementite-like carbides and borides of Groups VII-VIII transition metals (TMs) (M3X) were investigated.
Abstract: Density functional theory within the generalized gradient approximation (GGA) is used to investigate the electronic structure and formation energies of cementite-like carbides and borides of Groups VII–VIII transition metals (TMs) (M3X; where M=Fe, Co, Ni; X=C or B). All phases are metallic-like; Fe3C, Co3C, Fe3B and Co3B exhibit ferromagnetic states whereas Ni3C and Ni3B are paramagnetic. The formation energies of M3X calculated with respect to bulk TMs, graphite and α-boron (B12) are negative for borides, however, they are positive for carbides, i.e. these M3C phases are metastable or unstable at ambient conditions. The stability differences of these compounds are discussed in terms of their electronic structure and chemical bonding.
117 citations
TL;DR: The VULCAN diffractometer at the Spallation Neutron Source (SNS) is designed to tackle a broad range of problems in materials science and engineering, including spatial mapping of the residual stress distribution in components, deformation behavior under static and cyclic loadings, and the kinetics of the phase transformation as discussed by the authors.
Abstract: The VULCAN diffractometer at the Spallation Neutron Source (SNS) is designed to tackle a broad range of problems in materials science and engineering, including spatial mapping of the residual stress distribution in components, deformation behavior under static and cyclic loadings, and the kinetics of the phase transformation. The optics design features a focusing neutron guide, wide-angular detector coverage for diffraction, and an area detector for small angle scattering. By employing an interchangeable neutron guide-collimator system, the instrument can be optimally configured for individual experiments with desired resolution. The performance of the instrument was estimated using Monte Carlo simulation. A suite of specialized sample environments is also under construction as an integrated part of the instrument.
TL;DR: MERLIN as discussed by the authors is a high intensity, medium energy resolution spectrometer with a super-mirror guide to enhance flux and 3m long position-sensitive detectors in a vacuum.
Abstract: MERLIN is designed to be a high intensity, medium energy resolution spectrometer. As such, it will complement the high-resolution MAPS spectrometer at ISIS. MERLIN will utilise all the latest advances in technology with a supermirror guide to enhance flux as well as 3m long position-sensitive detectors in a vacuum making it ideal for single-crystal users. The detector bank will cover a massive pi steradians of solid angle with an angular range from -45 degrees to + 135 degrees degrees in the horizontal plane and +/- 30 degrees degrees in the vertical plane. This will allow large swathes of Q,omega space to be accessed in a single run. The instrument will be ready for commissioning in February 2006. This paper presents details of design and performance of this new instrument. (c) 2006 Elsevier B.V. All rights reserved.
TL;DR: In this article, the global magnetic phase diagram of Kondo lattice systems is analyzed and two classes of quantum critical point (QCP) classes are proposed, one of which describes a direct transition from a magnetic metal phase with localized f-electrons to a paramagnetic one with itinerant felectrons.
Abstract: We address the global magnetic phase diagram of Kondo lattice systems. Through the distinct Fermi surface properties of the various phases at zero temperature, we argue that the phase diagram supports two quantum critical point (QCP) classes. One of these describes a direct transition from a magnetic metal phase with localized f-electrons to a paramagnetic one with itinerant f-electrons. This result provides the context for the picture of local quantum criticality, in which the Fermi surface jumps across the QCP and the quasiparticle residue vanishes as the QCP is approached from either side. Some of the unusual experiments, concerning the phases and QCPs of heavy fermion metals, are discussed from the present perspective. These developments have implications in broader contexts. In particular, they form a part of the growing evidence for quantum criticality that goes beyond the orthodox description in terms of order-parameter fluctuations.
TL;DR: Neutron transmission tomography (NT) as mentioned in this paper is a technique that provides two- or three-dimensional maps of the attenuation coefficient distribution within an object by this means, the inner macroscopic structure and material composition can be visualized.
Abstract: Neutron transmission tomography is a technique providing two- or three-dimensional maps of the attenuation coefficient distribution within an object By this means, the inner macroscopic structure and material composition can be visualized Although basic principles are known since decades, this technique became more used in recent time, due to the availability of digital neutron area detectors and increased power of computers Modern neutron imaging detectors provide at the same time high sensitivity and sufficient spatial resolution Thus, objects in the size of a few millimeters up to tens of centimeters can be scanned in reasonable time Neutron tomography (NT) complements other computed tomography (CT) techniques like X-ray CT or nuclear magnetic resonance, due to the specific attenuation characteristics of thermal or cold neutrons NT can preferably be applied in cases where thick layers of (heavy) metals have to be transmitted and small amounts of light elements like hydrogen, boron, have to be detected We present methodological aspects specific for neutron transmission tomography Some recent results of NT investigations of scientific and technical relevance are given
TL;DR: In this paper, the Kramers-Kronig relationship was used to determine the optical parameters of ZnO:Al thin films in wavelengths with a range of 300-600 nm.
Abstract: ZnO:Al thin films doped with different aluminum concentration were deposited on (0001) sapphire substrates by sol-gel technique. Kramers-Kronig relationship was used to determine the optical parameters of ZnO:Al thin films in wavelengths with a range of 300-600 nm. Calculated results show that all optical parameters keep constant in the visible region. The refractive index, the extinction coefficient and the real and imaginary components of dielectric are similar to 1.6, similar to 0.08, similar to 2.5, and similar to 0.27, respectively. Optical constants change distinctly near the optical absorption edge. In the ultraviolet region, doping concentration strongly affects the optical parameters of ZnO:Al thin films. Optical parameters tend to decrease with increasing doping concentration. (c) 2006 Elsevier B.V. All rights reserved.
TL;DR: In this paper, the lattice parameters, elastic constants, bulk modulus and its pressure derivative of c-BN are calculated using a first-principles plane wave method with the relativistic analytic pseudopotential of the Hartwigen, Goedecker and Hutter (HGH) type and the pseudotype of Troullier Martins (TM)-type in the frame of local density approximation.
Abstract: The lattice parameters, elastic constants, bulk modulus and its pressure derivative of c-BN are calculated using a first-principles plane wave method with the relativistic analytic pseudopotential of the Hartwigen, Goedecker and Hutter (HGH)-type and the pseudopotential of Troullier Martins (TM)-type in the frame of local density approximation, and the dependences of bulk modulus on temperature and on pressure are investigated by the quasi-harmonic Debye model. The Debye temperature and the thermal expansion coefficient of c-BN are also calculated. The results obtained are well consistent with the available experimental data and other theoretical results. At zero pressure, the thermal expansion coefficients are about 6.0 x 10(-6) K-1 at T = 1724 K and 6.5 x 10(-6) K-1 at T = 1972 K, respectively, consistent with the experimental data. (c) 2006 Elsevier B.V. All rights reserved.
TL;DR: In this paper, the authors used optical confocal microscopy to study optical properties of diamond 50-nm nanocrystals first irradiated with an electron beam, then dispersed as a colloidal solution and finally deposited on a silica slide.
Abstract: We used optical confocal microscopy to study optical properties of diamond 50 nm nanocrystals first irradiated with an electron beam, then dispersed as a colloidal solution and finally deposited on a silica slide. At room temperature, under CW laser excitation at a wavelength of 514.5 nm we observed perfectly photostable single nitrogen-vacancy (NV) colour defects embedded in the nanocrystals. From the zero-phonon line around 575 nm in the spectrum of emitted light, we infer a neutral NV 0 type of defect. Such nanoparticle with intrinsic fluorescence are highly promising for applications in biology where long-term emitting fluorescent bio-compatible nanoprobes are still missing.
TL;DR: In this paper, the lattice constant and the grain size of tin-doped indium oxide (ITO) thin films with composition of 9.42% SnO 2 and 89.75% In 2 O 3, and impurities balanced have been prepared by electron beam evaporation on glass substrates with different deposition rates at fixed low substrate temperature condition.
Abstract: Tin-doped indium oxide (ITO) thin films with composition of 9.42 wt% SnO 2 and 89.75 wt% In 2 O 3 , and impurities balanced have been prepared by electron beam evaporation on glass substrates with different deposition rates at fixed low substrate temperature condition. Subsequently, the films were annealed at 400 °C in a thermal furnace for 1 h in air atmosphere. Hereafter, the films were quenched until room temperature and then have been characterized using X-ray diffraction and UV–visible spectroscopy. The lattice constant and the grain size of all thin films were derived to be 10.118 A and 37 nm in diameter, respectively. A transmittance value of 92% in the visible wavelength region at room substrate temperature was obtained. A similar value was already reported for high-level (20 wt%) tin-doped indium oxide thin films at 350 °C substrate temperature. The resistivity of the films was found to be 7×10 −4 Ω cm for the deposition rate of 0.05 nm s −1 . Results showed that by decreasing the deposition rate, a lower resistivity and a higher transmittance were obtained at the lower substrate temperature. The obtained values were better than those reported by other authors. Further optical studies showed that in these films allowed indirect transitions can take place. The direct optical energy gap deduced from the optical transmittance data using the Tauc relation was estimated to be 3.80 eV. Resistivity measurements showed that by decreasing the deposition rate, highly conductive transparent films can be obtained. Finally, it has been found that the deposition rate is a very important factor in controlling the electrical and optical properties of ITO films.
TL;DR: The microstructural and dielectric properties of La2/3Cu3Ti4O12 (LCTO) ceramics were found to be less sensitive to the sintering conditions.
Abstract: The microstructural and dielectric properties of La2/3Cu3Ti4O12 (LCTO) ceramics were found to be less sensitive to the sintering conditions. In contrast, these had imprinting effects on the dielectric characteristics of CaCu3Ti4O12 (CCTO) ceramics. The dielectric constant of CCTO increased drastically with increase in sintering temperature and duration as a consequence of significant change in the microstructural and compositional heterogeneity, while the increase was nominal in the case of LCTO ceramics. The dielectric behavior of both the ceramics was explained based on the Maxwell–Wagner relaxation arising mostly from the interfaces between grains and the grain boundaries.
TL;DR: In this paper, the violet emission originates from an electronic transition between the interstitial-zinc level and the valence band, or between the bottom of the conduction band and the V Zn level.
Abstract: Silver nanocluster doped ZnO thin films were fabricated on fused quartz substrates at different temperatures by pulsed laser deposition (PLD) using a silver-ZnO mosaic target. X-ray diffraction (XRD) measurements showed that ZnO and doped silver nanoclusters crystallized with preferred c-axis orientation. Scanning electron microscopic (SEM) images of the sample fabricated at 450 °C and the X-ray photoelectron spectroscopy (XPS) showed the radius of the silver clusters to be about 3–16 nm. Under 266 nm laser excitation, the photoluminescence (PL) spectra exhibited a peak at 414–420 nm for silver nanocluster doped ZnO thin films deposited at different temperatures. Through the investigation of the energy level of the defects in ZnO thin films, the energy levels of the zinc vacancy ( V zn , E V zn = 3 . 03 l eV ) and the interstitial zinc atom (Zni, E Zn i = 2.95 eV ) were found to be consistent with the peak wavelengths of 414 and 420 nm. We suggest that this violet emission originates from an electronic transition between the interstitial-zinc level and the valence band, or between the bottom of the conduction band and the V Zn level.
TL;DR: In this article, a general model for vector hysteresis is presented, which is in agreement with the required thermodynamical properties and with the macroscopic properties observed in the real media.
Abstract: A general model for vector hysteresis is presented. We will show that the model is in agreement with the required thermodynamical properties and with the macroscopic properties observed in the real media. Also the relationship with the Classical Preisach Scalar Model will be discussed.
TL;DR: The INTER reflectometer as discussed by the authors is a high resolution, high-flux neutron reflectometer for the study of chemical interfaces with particular emphasis on adsorption at the air-water interface.
Abstract: INTER is a high resolution, high-flux neutron reflectometer for the study of chemical interfaces with particular emphasis on adsorption at the air–water interface. One of the particular strengths of neutron reflection is that it can be applied to ‘wet’ interfaces to obtain information at better than molecular resolution. This, allied with H/D substitution, makes INTER especially suited to the study of chemical interfaces in soft condensed matter systems. INTER will improve upon the capabilities of the existing, world leading, reflectometers SURF and CRISP by make making use of an order of magnitude increase in neutron flux.
TL;DR: In this article, the fullpotential linearized augmented plane wave method (FP-LAPW) within the generalized gradient approximation (GGA) was used to calculate the electronic band structures and the total energies of BaS, CaSe and CaTe in NaCl and CsCl-type structures.
Abstract: The full-potential linearized augmented plane wave method (FP-LAPW) within the generalized gradient approximation (GGA) is used to calculate the electronic band structures and the total energies of BaS, CaSe and CaTe in NaCl and CsCl-type structures. The latter provide us with the ground states properties such as lattice parameter, bulk modulus and its pressure derivative, elastic constants and the structural phase stability of these compounds. The transition pressures at which these compounds undergo the structural phase transition from NaCl to CsCl phase are calculated. The energy band gaps and their volume dependence in NaCl and CsCl type-structures are investigated. The pressure and the volume at which band overlap metallization occurs are also determined. The ground state properties, the transition and metallization pressures (volumes) are found to agree with the experimental and other theoretical results. The elastic constants at equilibrium in both NaCl and CsCl structures are calculated and compared with the available theoretical results for CaSe, while for BaS and CaTe the elastic constants are not available.
TL;DR: In this paper, the nonlinear susceptibilities associated with intersubband transitions in the conduction band are theoretically calculated for CdSe/ZnS spherical core-shell quantum dots.
Abstract: The nonlinear susceptibilities associated with intersubband transitions in the conduction band are theoretically calculated for CdSe/ZnS spherical core–shell quantum dots. The confined wave functions and eigenenergies of electrons in quantum dots have been calculated under the effective-mass approximation by solving a three-dimensional Schrodinger equation. And the third-order susceptibilities for quadratic electro–optic effects as a function of core, shell radii, relaxation time and pump photo energy involving the position of energy levels also have been analyzed.
TL;DR: In this article, the spectral results of rare earth ion-doped B2O3-ZnO-PbO (BZP) glasses have been reported, and direct and indirect optical band gaps are calculated based on the glasses UV absorption spectra.
Abstract: This paper reports on the spectral results of Sm3+ or Dy3+ (1.0 mol%) ions-doped B2O3–ZnO–PbO (BZP) glasses. Measurements of X-ray diffraction (XRD), differential scanning calorimeter (DSC) profiles of these rare-earth ion-doped glasses have been carried out. From the DSC thermograms, glass transition (Tg), crystallization (Tc) and melting (Tm) temperatures have been evaluated. Direct and indirect optical band gaps have been calculated based on the glasses UV absorption spectra. These glasses have shown strong absorption bands in the near-infrared (NIR) region and their oscillator strengths have been computed. Emission bands of 4G5/2→6H5/2 (564 nm), 4G5/2→6H7/2 (602 nm), 4G5/2→6H9/2 (647 nm) and 4G5/2→6H11/2 (710 nm) for the Sm3+: glass, with excitation at 6H5/2→4I9/2 (484 nm) have been recorded. Of them, 4G5/2→ 6H7/2 (602 nm) has shown a bright emission. With regard to the Dy3+: glass, a bright fluorescent yellow emission at 576 nm (4F9/2→6H13/2) has been observed, apart from 4F9/2→6H15/2 (484 nm) and 4F9/2→6H11/2 (666 nm) emission transitions with excitation at 450 nm (6H15/2→4I15/2) excitation wavelength. Stimulated emission cross-sections of all the emission bands of Sm3+ and Dy3+: BZP glasses have been computed based on their measured Δλ (FWHM) and measured lifetimes (τm).
TL;DR: The Center for Structural Molecular Biology (CSMB) at Oak Ridge National Laboratory (ORNL) is developing facilities and techniques for the characterization and analysis of biological systems at the High Flux Isotope Reactor (HFIR) and the Spallation Neutron Source (SNS) as discussed by the authors.
Abstract: The Center for Structural Molecular Biology (CSMB) at Oak Ridge National Laboratory (ORNL) is developing facilities and techniques for the characterization and analysis of biological systems at the High Flux Isotope Reactor (HFIR) and the Spallation Neutron Source (SNS). The cornerstone of the effort is a small-angle neutron scattering instrument (Bio-SANS) currently under construction at HFIR that will be dedicated to the analysis of the structure, function and dynamics of complex biological systems. In support of this program, we are developing advanced computational tools for neutron analysis and modeling, alongside a supporting biophysical characterization and X-ray scattering infrastructure. Specifically, we established a Bio-Deuteration Laboratory for in vivo production of H/D-labeled macromolecules that will permit selected parts of macromolecular structures to be highlighted and analyzed in situ using neutron scattering. These new facilities will make ORNL a world-leading scientific center and user facility for neutron-based studies of biomolecular structure and function.
TL;DR: In this article, the authors applied the fullpotential linearized augmented plane wave (FP-LAPW) method to study the structural, elastic, electronic and optical properties of copper halides under high pressure using the local density approximation (LDA) and the generalized gradient approximation (GGA) for the exchange and correlation potential.
Abstract: We have applied the full-potential linearized augmented plane wave (FP-LAPW) method to study the structural, elastic, electronic and optical properties of copper halides CuX (X=Cl, Br, I) under high pressure using the local density approximation (LDA) and the generalized gradient approximation (GGA) for the exchange and correlation potential. We have calculated the ground-state energy, the lattice constant, the bulk modulus, and its pressure derivative in both NaCl (B1) and ZnS (B3) structures. A numerical first-principles calculation of the elastic constants was used to calculate C 11 , C 12 and C 44 . The pressures at which these compounds undergo a structural phase transition from ZnS type to NaCl type were calculated. Band structure, density of states and band gap–pressure coefficients in ZnS phase are also given. On the other hand, an accurate calculation of linear optical functions (refraction index and its pressure derivative, and both imaginary and real parts of the dielectric function) is performed in the photon energy range up to 11 eV. The results are compared with previous calculations and experimental measurements. We show that our calculated values compare acceptably well with values reported in the literature.
TL;DR: In this paper, the properties of the skutterudites AT4Sb12 filled with non-magnetic atoms, A=Ca, Sr, Ba and La, are found to depend strongly on the transition-metal elements, T=Fe, Ru and Os.
Abstract: Magnetic and thermoelectric properties of the skutterudites AT4Sb12 filled with non-magnetic atoms, A=Ca, Sr, Ba and La, are found to depend strongly on the transition-metal elements, T=Fe, Ru and Os. The strong spin fluctuations in the Fe-based compounds manifest themselves as an enhanced specific-heat coefficient γ=100 mJ/K2 mol. The maximum of the magnetic susceptibility at 50 K observed for A=Ca, Sr and Ba is a characteristic of a nearly ferromagnetic system. The increase of the paramagnetic Curie temperature from 3 to 54 K on going from A=La, Ba, Sr to Ca indicates the enhancement of ferromagnetic interactions in the Fe 3d narrow band. Except for A=La, a marked shoulder appears in the thermopower at 50 K which is totally suppressed by the application of a magnetic field of 14 T. The Ru compounds are metallic diamagnets with γ=10 mJ/K2 mol, while the Os compounds are strongly enhanced Pauli paramagnets with γ=45 mJ/K2 mol and show behaviors of a strongly coupled electron–phonon system. The lattice thermal conductivity for either A=La or T=Os does not show a peak near 50 K and its value is much smaller than other compounds. The strong phonon scattering can be caused by rattling of the relatively small La3+ ion in the T4Sb12 cage or tunneling of Sr2+ and Ba2+ ions in the Os4Sb12 cage.
TL;DR: In this paper, the effects of thermal annealing and dopant concentration on the optical properties of ZnO:Al thin films were investigated, and it was found that near band edge UV emission is enhanced by increasing the annesaling temperature and dopamine concentration.
Abstract: ZnO:Al thin films doped with different aluminum concentrations were deposited on (0001) sapphire substrates by the sol-gel technique. Thermal annealing of ZnO:Al films was carried out in an argon ambient at various annealing temperatures from 600 to 950 degrees C. The effects of thermal annealing and dopant concentration on the optical properties of ZnO:Al thin films were investigated. It is found that near band edge UV emission is enhanced by increasing the annealing temperature and dopant concentration. But defect-related deep-level emission decreases with the increasing dopant concentration and thermal annealing has little influence as the deep-level emission. The optical band gap of ZnO:Al films increases from 3.21 to 3.25 eV on increasing the dopant concentration from 0.01% to 1%. The optical transmittance decreases in the visible region, while it increases in the ultraviolet region with an increase in the annealing temperature. (c) 2006 Elsevier B.V. All rights reserved.
TL;DR: The first years of operation of the VIVALDI at the ILL were reviewed in this paper, where the Laue diffraction with image-plate detection on a thermal beam was described.
Abstract: The first years of operation of the Laue diffractometer VIVALDI at the ILL are reviewed. Neutron Laue diffraction with image-plate detection on a thermal beam is now a high-performance technique especially well suited to small crystals, rapid chemical crystallography, reciprocal-space surveys and studies of structural and magnetic phase transitions.