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Dopant Concentration (dopant + concentration)
Selected AbstractsEffects in B,doped KDP crystals irradiated with neutrons of large spectra energyCRYSTAL RESEARCH AND TECHNOLOGY, Issue 10 2004G. Fischfeld Abstract The results obtained for the r63 electro-optic coefficient of B-doped and undoped KDP (KH2PO4) crystals irradiated with neutrons (including thermalized neutrons) produced by scattering of 30 Mev cyclotron protons on a target of Ta201, are presented and compared to those obtained for non-irradiated doped and undoped crystals. The B-doped (H3BO3, Na2B4O7 and Li2B4O7) crystals were obtained by the conventional growth method by temperature decrease with 1 wt % dopant concentration in solution. The thermal neutron flux was around , = 1. 1010 n/cm2 s. Pulses of ,15 ,s long, in damped oscillatory mode (V= 8 kV, ,=1.95 ,s) were used for the electro-optic measurements. A Pockels cell, a photomultiplier, a He-Ne laser (,=632.8 nm, 5 mW, linearly polarized) and a Tk 720 A oscilloscope complete the experimental setup. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Phototunable Azobenzene Cholesteric Liquid Crystals with 2000 nm RangeADVANCED FUNCTIONAL MATERIALS, Issue 21 2009Timothy J. White Abstract Phototuning of more than 2000,nm is demonstrated in an azobenzene-based cholesteric liquid crystal (azo-CLC) consisting of a high-helical-twisting-power, axially chiral bis(azo) molecule (QL76). Phototuning range and rate are compared as a function of chiral dopant concentration, light intensity, and thickness. CLCs composed of QL76 maintain the CLC phase regardless of intensity or duration of exposure. The time necessary for the complete restoration of the original spectral properties (position, bandwidth, baseline transmission, and reflectivity) of QL76-based CLC is dramatically reduced from days to a few minutes by polymer stabilization of the CLC helix. [source] Synthesis of Luminescent ZrO2:Eu3+ Nanoparticles and Their Holographic Sub-Micrometer Patterning in Polymer CompositesADVANCED FUNCTIONAL MATERIALS, Issue 11 2009Tsedev Ninjbadgar Abstract Here, the facile synthesis of fluorescent ZrO2:Eu3+ nanoparticles with luminescence quantum yield of up to 8.7% that can be easily dispersed in organic solvents and utilized for the preparation of organic/inorganic volume holographic gratings is presented. The nanoparticles are prepared through a one-step solvothermal process resulting in spherical particles with a mean size of 4,nm that were highly crystalline directly after the synthesis, without any need for calcination treatment. Detailed luminescence studies of the nanoparticles as a function of Eu3+ content demonstrate that the dopant concentration and its site symmetry play an important role in the emissive properties and lifetime of the luminescent centers. It is shown that the luminescence quantum yield of the colloidal ZrO2:Eu3+ nanoparticles increases with dopant concentration up to a critical concentration of 11 mol% while the luminescence lifetime is shortened from 1.8 to 1.4 ms. Holographic photopolymerization of suitable monomer mixtures containing the luminescent nanoparticles demonstrated the ability to inscribe volume Bragg gratings (refractive index contrast n1 up to 0.011) with light-emissive properties, evidencing the high suitability of this approach for the fabrication of tailored nanomaterials for elaborate and demanding applications. [source] Atomistic analysis of B clustering and mobility degradation in highly B-doped junctionsINTERNATIONAL JOURNAL OF NUMERICAL MODELLING: ELECTRONIC NETWORKS, DEVICES AND FIELDS, Issue 4-5 2010Maria Aboy Abstract In this paper we discuss from an atomistic point of view some of the issues involved in the modeling of electrical characteristics evolution in silicon devices as a result of ion implantation and annealing processes in silicon. In particular, evolution of electrically active dose, sheet resistance and hole mobility has been investigated for high B concentration profiles in pre-amorphized Si. For this purpose, Hall measurements combined with atomistic kinetic Monte Carlo atomistic simulations have been performed. An apparent anomalous behavior has been observed for the evolution of the active dose and the sheet resistance, in contrast to opposite trend evolutions reported previously. Our results indicate that this anomalous behavior is due to large variations in hole mobility with active dopant concentration, much larger than that associated to the classical dependence of hole mobility with carrier concentration. Simulations suggest that hole mobility is significantly degraded by the presence of a large concentration of boron-interstitial clusters, indicating the existence of an additional scattering mechanism. Copyright © 2009 John Wiley & Sons, Ltd. [source] Microstructure of Nanocrystalline Yttria-Doped Zirconia Thin Films Obtained by Sol,Gel ProcessingJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2008Benjamin Butz Nano- and microcrystalline yttria-stabilized zirconia (YSZ) thin films with a dopant concentration of 8.3±0.3 mol% Y2O3 were prepared with a variation in grain size by two orders of magnitude. A sol,gel-based method with consecutive rapid thermal annealing was applied to fabricate YSZ films, resulting in about 400 nm YSZ on sapphire substrates. The average grain sizes were varied between 5 nm and 0.5 ,m by heat treatment in the temperature range of 650°,1350°C for 24 h. High-resolution (HRTEM) and conventional transmission electron microscopy analyses confirmed specimens,irrespective of the thermal treatment,consisting of cubic (c -)ZrO2 grains with nanoscaled tetragonal precipitates coherently embedded in the cubic matrix. Energy-dispersive X-ray spectroscopy and HRTEM on a large number of specimens yielded a homogeneous yttria concentration within the grains and at the grain boundaries with the absence of impurities, i.e. silica at the grain boundaries. [source] Synthesis and Characterization of Ce1,xGdxO2,, NanorodsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2007Jong Soo Lee Single crystalline Ce1,xGdxO2,, nanorods with x=0.05 and 0.1 as well as x=0 were synthesized by a sol,gel process without using any template and/or applying high pressure. The nanorods grow preferentially along the [110] direction regardless of the dopant concentration. The diameter and the length of the synthesized nanorods range from 10 to 50 nm and from 200 to 700 nm, respectively. The length of the nanorods decreases with increasing dopant concentration. The role of the surfactant as a structure-directing agent is critical to the growth of Ce1,xGdxO2,, nanorods. [source] Electrical Conductivities of (CeO2)1,x(Y2O3)x Thin FilmsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2002Chunyan Tian Electrical properties of CeO2 thin films of different Y2O3 dopant concentration as prepared earlier were studied using impedance spectroscopy. The ionic conductivities of the films were found to be dominated by grain boundaries of high conductivity as compared with that of the bulk ceramic of the same dopant concentration sintered at 1500°C. The film grain-boundary conductivities were investigated with regard to grain size, grain-boundary impurity segregation, space charge at grain boundaries, and grain-boundary microstructures. Because of the large grain boundary and surface area in thin films, the impurity concentration is insufficient to form a continuous highly resistive Si-rich glassy phase at grain boundaries, such that the resistivity associated with space-charge layers becomes important. The grain-boundary resistance may originate from oxygen-vacancy-trapping near grain boundaries from space-charge layers. High-resolution transmission electron microscopy coupled with a trans-boundary profile of electron energy loss spectroscopy gives strong credence to the space-charged layers. Since the conductivities of the films were observed to be independent of crystallographic texture, the interface misorientation contribution to the grain-boundary resistance is considered to be negligible with respect to those of the impurity layer and space-charge layers. [source] Compensation in boron-doped CVD diamondPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 9 2008Markus Gabrysch Abstract Hall-effect measurements on single crystal boron-doped CVD diamond in the temperature interval 80,450 K are presented together with SIMS measurements of the dopant concentration. Capacitance,voltage measurements on rectifying Schottky junctions manufactured on the boron-doped structures are also presented in this context. Evaluation of the compensating donor (ND) and acceptor concentrations (NA) show that in certain samples very low compensation ratios (ND/NA below 10,4) have been achieved. The influence of compensating donors on majority carrier transport and the significance for diamond device performance are briefly discussed. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Laser-doping of silicon carbide for p,n junction and LED fabricationPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 4 2007Sachin Bet Abstract The high melting point and the limited diffusion of impurities in silicon carbide have greatly restricted the use of conventional ion implantation and furnace to incorporate and activate dopants. A laser doping technique overcomes these obstacles for doping silicon carbide and other wide band gap semiconductors. This paper presents the work on fabrication of p,n junction diodes and blue light emitting diodes using laser doping technique. A p,n junction was created by laser doping a silicon carbide wafer with aluminum (p-type) and nitrogen (n-type). Optical interferometer profilometer scan showed that there was no damage on the surface post laser doping. Secondary ion mass spectrometry (SIMS) was carried to estimate the dopant concentration and depth. The effects of laser doping on the current,voltage characteristics were studied. The junctions were characterized by capacitance,voltage and electroluminescence measurements. A broad electroluminescence peak was observed around 498.8 nm wavelength, characterizing the p,n junction as a blue light-emitting diode. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Transport properties of hydrogen-doped (Zr803d20)1,xHx (3d = Co, Ni) metallic glassesPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 4 2004I. Kokanovi Abstract The electrical resistivities of hydrogen-doped (Zr803d20)1,xHx (3d = Ni, Co; x , 0.11) metallic glasses have been measured at temperatures between 2 K and 110 K and in magnetic fields up to 1 T for various dopant concentrations. These systems have a high room-temperature resistivity (, > 160 ,, cm) and become superconducting below 4 K. The increase of the room-temperature resistivity and its temperature coefficient with hydrogen dopant concentration is explained as due to an increase of disorder with hydrogen-doping. The temperature and magnetic field dependence of the resistivity has been analysed using theoretical models of weak-localisation and electron,electron interaction in disordered conductors. The hydrogen dopant is found to reduce the effective electron diffusion constant, D, the spin-orbit scattering rate, ,,1so, the superconducting transition temperature, Tc, and broadens the superconducting transition region. The contribution of the Maki-Thompson interaction to the magnetoresistivity is also reduced. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Porous silicon surfaces for metabonomics: Detection and identification of nucleotides without matrix interferencePHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2007D. Gómez Abstract In present work, porous silicon surfaces (PSS) have been developed for time of flight mass spectrometric experiments (TOF-MS) in the monitoring of nucleotides, commonly found as metabolites in the cell. The mass range of the studied molecules (, 400 amu) is common to several important messengers and other metabolites. Different porosified surfaces have been developed by means of electrochemical etching and different degree of porosity and pore size achieved as function of silicon dopant concentration, silicon resistivity, current density and the presence or absence of illumination along the process. As main conclusion, it can be said that an interesting commercial nucleotide (Cyclic adenosine monophosphate, c-AMP) has been detected on low concentrations (,hundreds of femtomols) for some of the fabricated porous surfaces. Taking into account that these concentrations are similar to the ones found in real samples, this result opens the possibility to the fabrication of DIOS (Desorption Ionization On Silicon) chips for the detection of nucleotides in biological fluids. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] First-principles calculation of electronic structure of V-doped anatase TiO2CHEMPHYSCHEM, Issue 12 2010Run Long Dr. Abstract The energetic and electronic structures of V-doped anatase TiO2 have been investigated systematically by the GGA+U approach, including replacement of Ti by V in the absence and presence of oxygen vacancies and the presence of an interstitial site. It was found that V should exist as a V4+ ion in the replacement of Ti in the anatase lattice, the electron transitions of which to the conduction band from V,3d states are responsible for the experimentally observed visible light absorption. The influence of V dopant concentration on the electronic and magnetic properties is also discussed, such as the influence of the U value in systems containing oxygen vacancies and spin flip phenomena for interstitial V-doping. [source] Preparation and self-assembly of polyaniline nanorods and their application as electroactive actuatorsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2010Seong Hun Kim Abstract To improve the performance of ion-exchange polymer,metal composite (IPMC) actuators, an electrical pathway material for enhancing the surface adhesion between the membrane and the metal electrodes of the IPMC was studied. As an efficient electrical pathway material, polyaniline nanorods (PANI-NRs) doped with p -toluene sulfonic acid (TSA) were synthesized with a template-free method. The factors affecting polyaniline morphology were studied with various dopant concentrations and oxidant feeding rates. Highly conductive PANI-NRs were formed when they were synthesized with ammonium persulfate at a 5.0 mL/min oxidant feeding rate and doped with 0.125M TSA. The conductivity of the PANI-NRs was 1.15 × 10,1 S/cm, and their diameters and lengths were 120,180 nm and 0.6,2 ,m, respectively. To apply the membrane as an actuator, perfluorosulfonated ionomer (Nafion)/PANI-NR blends were prepared by solution blending and casting. The actuating ability of the three-layered membrane consisting of Nafion/PANI-NR blends was then examined and compared with that of Nafion only. The actuating ability of the IPMC was improved when Nafion/PANI-NRs were used as electrical pathways. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Transport properties of hydrogen-doped (Zr803d20)1,xHx (3d = Co, Ni) metallic glassesPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 4 2004I. Kokanovi Abstract The electrical resistivities of hydrogen-doped (Zr803d20)1,xHx (3d = Ni, Co; x , 0.11) metallic glasses have been measured at temperatures between 2 K and 110 K and in magnetic fields up to 1 T for various dopant concentrations. These systems have a high room-temperature resistivity (, > 160 ,, cm) and become superconducting below 4 K. The increase of the room-temperature resistivity and its temperature coefficient with hydrogen dopant concentration is explained as due to an increase of disorder with hydrogen-doping. The temperature and magnetic field dependence of the resistivity has been analysed using theoretical models of weak-localisation and electron,electron interaction in disordered conductors. The hydrogen dopant is found to reduce the effective electron diffusion constant, D, the spin-orbit scattering rate, ,,1so, the superconducting transition temperature, Tc, and broadens the superconducting transition region. The contribution of the Maki-Thompson interaction to the magnetoresistivity is also reduced. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Influence of Mg Doping on GaN NanowiresCHEMPHYSCHEM, Issue 3 2009Dongdong Zhang Abstract Magnesium-doped GaN nanowires with different dopant concentrations are synthesized and their morphology, structure, growth properties, crystallinity, and optical properties investigated. The nanowires are single-crystalline with hexagonal wurzite structure, and doping with 5 atom,% of Mg gives nanowires with the best morphology and crystallinity (see HRTEM image). Magnesium-doped GaN nanowires with different dopant concentrations are synthesized by ammoniating Ga2O3 thin films doped with Mg at 900,°C. Scanning electron microscopy (SEM), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), high-resolution transmission electron microscopy (HRTEM), and room-temperature photoluminescence (PL) are employed to characterize the influences on the morphology, structure, crystallinity, and optical properties of Mg-doped GaN nanowires. The results demonstrate that the nanowires are single-crystalline with hexagonal wurzite structure. GaN nanowires doped with 5 atom,% of Mg have the best morphology and crystallinity with a single-crystalline structure, and at this composition the PL spectrum with the strongest UV peak is observed. The growth mechanism of crystalline GaN nanowires is discussed briefly. [source] Studies on electrical conduction behavior of La1-3xCaxBaxSrxMnO3 synthesized by chemical routeCRYSTAL RESEARCH AND TECHNOLOGY, Issue 3 2008K. D. Mandal Abstract In the manganite La1-xMxMnO3 (M = Ca, Ba, Sr) the doping concentration introduces a mixed valency (Mn3+, Mn4+) which governs the magnetic and electrical properties of the compound. The perovskite oxides La1-3xCaxBaxSrxMnO3 (x = 0.00, 0.05, 0.10) were prepared by chemical method. Single-phase formation is confirmed by XRD studies. The electrical behavior of compositions with x = 0.00, 0.05 and 0.10 in the system La1-3xCaxBaxSrxMnO3 was studied in the temperature range 300-420 K. It is observed that conductivity decreases with increasing temperature as well as dopants concentration. Metallic behavior of these compositions decreases with increasing dopants concentration (x). The microstructures of these samples have been characterized using scanning electron microscopy (SEM). (© 2007 WILEY -VCH Verlag GmbH & Co. KGaA, Weinheim) [source] The electronic and optical properties of oligo(trans -1,2-di(2-thienyl)-1,3-butadiene): A theoretical studyINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 13 2008Nei Marçal Abstract In the present work we investigated the theoretical electronic structure of poly(trans -1,4-di(2-thienyl)-1,3-butadiene) (PTB) and determined the optical properties of its neutral and doped oligomers. Geometrical optimizations were at the semiempirical level by using the Austin method 1 (AM1). The band structure of , electrons regarding to the neutral PTB polymer was obtained by using a tight-binding Hamiltonian. The densities of electronic states (DOS) for neutral and doped copolymers were calculated by using the negative factor counting technique. The spatial charge distribution of the oligomeric chain was also analyzed. The energy of the electronic transitions and their associated oscillator strength values were calculated for the neutral, double, and single charged oligomers to determine the UV,vis absorption spectra. The calculations were performed using the intermediate neglect of differential overlap Hamiltonian in combination with the single configuration-interaction technique in order to include correlation effects. The band gap obtained in the PTB was about 2.101 eV for the optics absorption and 1.73 eV for the DOS. The bipolaron states appear in the gap, about 0.57 eV and 0.48 eV below and above the conduction and valence bands, respectively. When the dopants concentration is increased the DOS showed that the energy gap tends to vanish, which may lead to semiconductor,metal transition. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008 [source] |