Showing papers in "European Physical Journal-applied Physics in 2007"
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TL;DR: An objective analysis is carried out of the matricial models representing the polarimetric properties of light and material media leading to the identification and definition of their corresponding physical quantities, using the concept of the coherency matrix, which constitutes a powerful tool for analyzing and exploiting experimental and industrial polarimetry.
Abstract: An objective analysis is carried out of the matricial models representing the polarimetric properties of light and material media leading to the identification and definition of their corresponding physical quantities, using the concept of the coherency matrix. For light, cases of homogeneous and inhomogeneous wavefront are analyzed, and a model for 3D polarimetric purity is constructed. For linear passive material media, a general model is developed on the basis that any physically realizable linear transformation of Stokes vectors is equivalent to an ensemble average of passive, deterministic nondepolarizing transformations. Through this framework, the relevant physical quantities, including indices of polarimetric purity, are identified and decoupled. Some decompositions of the whole system into a set of well-defined components are considered, as well as techniques for isolating the unknown components by means of new procedures for subtracting coherency matrices. These results and methods constitute a powerful tool for analyzing and exploiting experimental and industrial polarimetry. Some particular application examples are indicated.
239 citations
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TL;DR: In this paper, a solution to heat equation in particular cases of uniform and non-uniform fluid deposit is yielded as a guide to geometrical and temporal parameters control for pyrolysis spray disposal performance.
Abstract: This paper proposes concrete enhancement of pyrolysis spray disposal performance. Solution to heat equation in particular cases of uniform and non-uniform fluid deposit is yielded as a guide to geometrical and temporal parameters control. Implemented models take into account simultaneously deposited material and targeted device thermal and geometrical properties. Theoretical temperature time-response features are compared to experiment in order to enhance deposition and solidification processes.
97 citations
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TL;DR: In this article, the authors demonstrate that thermal treatment of P3HT/PCBM films prepared from CB solution results in a decrease of the charge transfer yields, and that the improved performance of solar cells is attributed to optimization of the morphology, in particular molecular order in the P3H regions, which could be monitored by optical absorption and resonant Raman scattering.
Abstract: We demonstrate, by means of light-induced EPR and optical spectroscopy, that thermal treatment of P3HT/PCBM films prepared from CB solution results in a decrease of the charge transfer yields. The improved performance of solar cells is therefore attributed to optimization of the morphology, in particular molecular order in the P3HT regions, which could be monitored by optical absorption and resonant Raman scattering (RRS). We further found that spin coating from slowly evaporating solvents leads directly (i.e., without thermal treatment) to optimal morphologies of the P3HT/PCBM films, with similar results for charge transfer, morphology and solar cell efficiencies.
76 citations
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TL;DR: In this paper, a spray pyrolysis technique was used to prep fluorine doped tin oxide (FTO) thin films with no further annealing and showed homogeneous surfaces with average grain size around 190nm.
Abstract: Fluorine doped tin oxide (FTO) thin films have been prepared by spray pyrolysis technique with no further annealing. Films with 2.5% of fluorine grown at 400 °C present a single phase and exhibit a tetragonal structure with lattice parameters a = 4.687 A and c = 3.160 A. Scanning electron micrographs showed homogeneous surfaces with average grain size around 190 nm. The films are transparent in the visible zone and exhibit a high reflectance in the near infrared region. The best electrical resistivity was 6.3 × 10 -4 Ω cm for FTO with 2.5% of fluorine. The ratio of transmittance in the visible to the sheet resistance are in the 0.57 × 10 -2 –1.96 × 10 -2 Ω -1 range.
61 citations
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TL;DR: A general triangle mapped onto a computational domain is considered and the Navier-Stokes equations in general curvilinear coordinates in streamfunction and vorticity formulation are numerically solved.
Abstract: Numerical solutions of 2-D steady incompressible flow inside a triangular cavity are presented. For the purpose of comparing our results with several different triangular cavity studies with different triangle geometries, a general triangle mapped onto a computational domain is considered. The Navier-Stokes equations in general curvilinear coordinates in streamfunction and vorticity formulation are numerically solved. Using a very fine grid mesh, the triangular cavity flow is solved for high Reynolds numbers. The results are compared with the numerical solutions found in the literature and also with analytical solutions as well. Detailed results are presented.
49 citations
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TL;DR: In this paper, an electrical model for a dielectric barrier discharge (DBD) is proposed, with the aim of its application in power supply design process, and an identification method, which finds the actual value of the parameters in a model, is presented.
Abstract: An electrical model for a dielectric barrier discharge(DBD) is proposed, with the aim of its application in power supply design process. An identification method, which finds the actual value of the parameters in a model, is presented. The specific modelling of a XeCl exciplex lamp is developed, along with the identification procedure of the parameters, using a sinusoidal and a pulsed experiment. Electrical representation of the model is done in two different simulators. The applicability of the identified model is proved with different experiments. Differences between experimental and simulated waveforms are minor, encouraging the use of the model in the construction of the converter for the DBD lamp.
48 citations
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TL;DR: In this article, the use of CR-39, a solid state nuclear track detector, to detect the emission of energetic charged particles during Pd/D co-deposition is demonstrated.
Abstract: The use of CR-39, a solid state nuclear track detector, to detect the emission of energetic charged particles during Pd/D co-deposition is demonstrated. The pits observed in the CR-39 are attributed to the Pd/D cathode and are not due to radionuclide contamination in the cell components; nor to the impingement of D2 bubbles on the surface of the CR-39; nor to chemical attack by D2, O2, or Cl2. The features (i.e., optical contrast, shape, and bright spot in the center of the pit) of the pits generated during Pd/D co-deposition are consistent with those observed for pits that are of a nuclear origin.
48 citations
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TL;DR: In this article, the mean free path of charge carriers in CoPc thin films and bulk resistivity was estimated using the CBH model with centers of intimate valence alternation pairs type with a maximum barrier height of 1.594 eV.
Abstract: Thin films of CoPc of various thickness have been deposited onto glass substrates using thermal evaporation technique at room temperature. The dark electrical resistivity measurements were carried out at different temperature range (298–423 K). An estimation of mean free path () of charge carriers in CoPc thin films and bulk resistivity, was attempted. Measurements of thermoelectric power confirm that CoPc thin films behave as p -type semiconductors. The ac conductivity ( σ ac ) has been investigated in the frequency range (10 2 –10 6 Hz) and temperature range (298–407 K). σ ac is found to be proportional to ω s where s ≈ 0.879 which is frequency and temperature independence. The ac conductivity interpreted by the correlated barrier hopping (CBH) model with centers of intimate valence alternation pairs type with a maximum barrier height, W M ≈ 1.594 eV.
38 citations
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TL;DR: In this paper, thin lead sulfide films were grown on single crystal GaAs(100) substrates by chemical deposition using Pb(NO 3 ) 2 and CS(NH 2 ) 2 with excess of NaOH in aqueous solution at a range of deposition temperatures 0-50°C.
Abstract: Thin lead sulfide films were grown on single crystal GaAs(100) substrates by chemical deposition using Pb(NO 3 ) 2 and CS(NH 2 ) 2 with excess of NaOH in aqueous solution at a range of deposition temperatures 0–50 °C. The microstructure and morphology evolution were studied as a function of the deposition conditions, resulting in a wide range of microstructures. Ultrahigh resolution scanning electron microscopy and atomic force microscopy indicated a systematic change in particle shape and surface morphology as a function of deposition temperature and deposition time. X-ray diffraction of 200–500 nm thick films indicated a dominant texture throughout the deposition temperature range. At deposition temperatures above 40 °C, single crystal films were obtained. Cross-sectional transmission electron microscopy analyses showed a unique (011) PbS ||(100) GaAs and [100] PbS ||[011] GaAs orientation relationship.
37 citations
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TL;DR: In this paper, the authors proposed to use transparent contacts on both sides of the diode, leading to brilliant red-coloured semitransparent solar cells for new, aesthetically appealing applications where coloured glasses or foils with the additional benefit of providing electric power are desired.
Abstract: The optical absorption in organic solar cells, and hence their
efficiency to convert sunlight into electricity, is limited
by both a confined spectral absorption range and the very thin active layers which are required since polymers have short charge carrier diffusion
lengths. We propose to make the most of this
apparent 'drawback' by using transparent contacts on both sides of
the diode, leading to brilliant red-coloured semitransparent solar
cells. Such cells are interesting for new, aesthetically appealing
applications where coloured glasses or foils with the additional
benefit of providing electric power are desired. Maybe even more
importantly – such semitransparent solar cells are essential for
mechanically stacked tandem arrays where two subcells are
combined. We investigated different cathodes based on Al-doped ZnO and thin LiF and Al layers. Apparently, the different cathode layer preparation conditions strongly influence the cell
performance. Our standard LiF/Al cells do
not usually require annealing for improved efficiencies, in
contrast to cells with sputtered cathodes. For the latter, a
thermal post-treatment can greatly enhance the performance,
depending on the sputtering process. We could demonstrate power conversion efficiencies of up to 3.4% for single cells and up to 4.2% for stacked tandem arrays.
33 citations
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TL;DR: In this article, the authors derived the drain current as a function of gate voltage (transconductance), leading to the so-colled field effect mobility of polycrystalline octithiophene transistors.
Abstract: Organic field-effect transistors (OFETs) in which the active semiconductor is made of polycrystalline octithiophene (8T) were fabricated and characterized. Several methods have been used to extract the parameters of the polycrystalline (8T) transistors as function of gate voltage at room and at low temperatures. These parameters such as the mobility, the threshold voltage, contact resistance and density of traps are extracted from the current-voltage characteristics of OFETs. The first method consists of deriving the drain current as function of gate voltage (transconductance), leading to the so-colled field effect mobility. It appears that the data must be corrected for the substantial source and drain contact resistance. In the second method, the carrier mobility has been corrected for the contact resistance. It is found to increase quasi linearly with gate voltage. Therefore, the contact resistances have been directly extracted from the experimental channel conductance. In the third method, data are interpreted according the multiple thermal trapping and release model using a power law dependence of the mobility with gate voltage together with a constant resistance. Finally, using a model where charge transport is limited by trapping and thermal release at localized states located at grain boundaries, the barrier height at grain boundaries in polycrystalline octhithiophene FETs has been estimated. It is shown that is gate bias dependent.
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TL;DR: In this paper, the influence of an exciton blocking layer and/or an Al 2 O 3 thin layer at the interface "organic acceptor/aluminium" on the efficiency of CuPc/C 60 based photovoltaic cells was reported.
Abstract: We report the influence of an exciton-blocking layer and/or an Al 2 O 3 thin layer at the interface “organic acceptor/aluminium” on the efficiency of CuPc/C 60 based photovoltaic cells. The presence, or not, of a thin Al 2 O 3 layer depends on the encapsulating process of the devices. In the case of glass/ITO/CuPc/C 60 /Al cells, the presence of an Al 2 O 3 thin layer at the interface “organic acceptor/aluminium” increases strongly the open circuit voltage of the cells but decreases slightly their short circuit current and fill factor. In the case of glass/ITO/CuPc/C 60 /Alq 3 /Al cells, the open circuit voltage is systematically higher than without Alq 3 . However, in that case, the presence of Al 2 O 3 does not improve significantly the cell performances. All these results are discussed in terms of series and shunt resistance values related to possible oxygen contamination and organic covalent action with the Al films. The effectiveness of these different phenomena depends on the presence, or not, of Alq 3 and/or Al 2 O 3 layers.
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TL;DR: It is deduced that a seven-phase machine is a good compromise allowing high torque-to-volume density and easy control with smooth torque in fault operation.
Abstract: This paper deals with fault tolerant multiphase electrical drives. The quality of the torque of a vector-controlled Permanent Magnet (PM) Synchronous Machine supplied by a multi-leg Voltage Source Inverter (VSI) is examined in normal operation and when one or two phases are open-circuited. It is then deduced that a seven-phase machine is a good compromise allowing high torque-to-volume density and easy control with smooth torque in fault operation. Experimental results confirm the predicted characteristics.
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TL;DR: In this paper, a model organic material, namely the 36-nalkane hexatriacontane, was etched in a dissymmetrical parallel plate RF plasma reactor and a dual distributed electron cyclotron resonance (DECR) plasma reactor, in different O 2 -Ar mixtures.
Abstract: A model organic material, namely the 36-n-alkane hexatriacontane, was etched in a dissymmetrical parallel plate RF plasma reactor and a dual distributed electron cyclotron resonance (DECR) plasma reactor, in different O 2 -Ar mixtures. A specific attention was paid to the role of the ion bombardment, especially when its effect is combined with the chemically active species created in an oxygen discharge. The discharge was monitored by optical emission spectroscopy (OES). The modifications induced by plasma treatment on the structure of the material were analysed by Fourier transform infrared spectroscopy (FTIR), steric exclusion chromatography (SEC) and composition analysis. We found that the ion bombardment has not only a sputtering effect but also enhances the reaction rate of the chemical species on the layer surface. It appears that plasma treatment leads to cross-linking and recombination with molecules from the room atmosphere.
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TL;DR: In this paper, the authors measured the secondary electron emission yield (SEE yield) in a dedicated scanning electron microscope especially equipped to study the fundamental aspects of the charge transport and trapping in insulating materials.
Abstract: Foils of Polymethyl methacrylate (PMMA) 2 mm thick were studied by measuring the total Secondary Electron Emission yield (SEE yield) in a dedicated Scanning Electron Microscope especially equipped to study the fundamental aspects of the charge transport and trapping in insulating materials. The intrinsic SEE yield , (yield of the uncharged material) and the charging kinetics were studied under low current density pA/cm2. The curve of the primary beam energy variation of exhibits a maximum intrinsic yield at 370 ± 20 eV and two crossover energies ± 20 eV and ± 20 eV for which . For 1 PMMA is positively charged and negatively for 1. As electron injection is proceeding under the low current density used, the SEE yield varies from to the steady value . This value that expresses the equality between the average number of emitted and injected electrons, characterizes the steady charge regime called “Self-Regulated Regime”. The evolution of during the injection process is due to the internal field that blocks or enhances the secondary electron emission, according to the positive or negative nature of the trapped charges. A current density effect, characterized by a steady SEE yield slightly higher than unity, , instead of one, is observed at high energy (for example 4000 eV) for a strong current density $J>10^{+6 }$ pA/cm2. It is interpreted by a field ionisation (Poole-Frenkel type) that enhances the secondary electron emission.
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TL;DR: In this paper, the mechanical Q-factor measurements of single crystalline calcium fluoride CaF 2 bulk material were presented, where the substrate was suspended as a pendulum by means of a tungsten wire loop.
Abstract: Mechanical Q -factor measurements of single crystalline calcium fluoride CaF 2 bulk material are presented. Resonant modes between 27 and 100 kHz were investigated on a cylindrical test sample (). For selected modes low temperature measurements of the mechanical Q -factor were done within a temperature range from 5 to 300 K. For the Q -measurements a ring-down technique was used. The substrate was suspended as a pendulum by means of a tungsten wire loop. The highest Q -factor has been achieved around 60 K with 3 × 10 8 which is the highest Q -factor reported on CaF 2 up to now.
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TL;DR: In this article, structural properties of liquid and amorphous Al 2 O 3.2SiO 2 (denoted as AS2) have been studied in a model containing 3025 particles under periodic boundary conditions with the Born-Mayer type pair potentials.
Abstract: Structural properties of liquid and amorphous Al 2 O 3 .2SiO 2 (denoted as AS2) have been studied in a model containing 3025 particles under periodic boundary conditions with the Born-Mayer type pair potentials. Models have been obtained by cooling from the melt via molecular dynamics (MD) simulation. Structural properties of an amorphous model obtained at the temperature of 350 K have been analyzed in details through the partial radial distribution functions (PRDF), coordination number distribution, bond-angle distributions and interatomic distances. Calculations show that calculated data agree well with the experimental ones and with those obtained previously in other simulation works. The evolution of structure upon cooling from the melt was observed and discussed. We found a clear evidence of the existence of triclusters in the system. Diffusion constant of particles has been calculated and discussed. Calculations presented that the temperature dependence of diffusion constant D of components in the system shows an Arrhenius law at temperatures ranged from 2450 K to 4200 K and it shows a power law, $D\propto (T-T_C )^\gamma$
, at higher temperatures.
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TL;DR: In this paper, various geometrical designs of single point defects and double heterostructures for the formation of high Q nanocavities in diamond are modeled, and the highest value of vertical quality factor was achieved in double heterstructures, which is significant for further consideration of photonic crystals in diamond for quantum electrodynamics applications.
Abstract: A slab two-dimensional photonic crystal in diamond is being considered for quantum information processing. In view of the low refractive index of diamond, the question whether a high Q cavity is achievable has to be addressed. Here, various geometrical designs of single point defects and double heterostructures for the formation of high Q nanocavities in diamond are modeled. The highest value of vertical quality factor was achieved in double heterostructures. This result seems to be significant for further consideration of photonic crystals in diamond for quantum electrodynamics applications.
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TL;DR: PbO-Sb2O 3 -B 2 O3 glasses containing different concentrations of MoO 3 ranging from 0 to 5 mol % were prepared and a number of studies were carried out on these glasses comprising differential thermal analysis, infrared and optical absorption, Raman and ESR spectra, magnetic susceptibility and measurements of dielectric properties (constant e', loss tan δ and a.c. conductivity σ ac. over a range of frequency and temperature) of these glasses as mentioned in this paper.
Abstract: PbO-Sb2O 3 -B 2 O3 glasses containing different concentrations of MoO 3 ranging from 0 to 5 mol % were prepared. A number of studies have been carried out on these glasses comprising differential thermal analysis, infrared and optical absorption, Raman and ESR spectra, magnetic susceptibility and measurements of dielectric properties (constant e', loss tan δ and a.c. conductivity σ ac . over a range of frequency and temperature) of these glasses. The results have been analyzed in terms of different oxidation states of molybdenum ions. The'analysis indicates that when the concentration of MoΟ 3 is <0.6 mol %, molybdenum ions exist mostly in the Mo 6+ state, occupy network forming positions with MoO 2- 4 structural units and increase the rigidity of the glass network. When MoO 3 is present in higher concentrations, molybdenum ions seem to exist mostly in the Mo 5+ state and occupy modifying positions.
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TL;DR: In this article, the authors present results on the realization of a multicolour microspherical glass light source fabricated from the erbium doped fluoride glass ZBLALiP.
Abstract: We present results on the realization of a multicolour microspherical glass light source fabricated from the erbium doped fluoride glass ZBLALiP. Whispering gallery mode lasing and upconversion processes give rise to laser and fluorescent emissions at multiple wavelengths from the ultraviolet to the infrared. Thirteen discrete emissions ranging from 320 to 849 nm have been observed in the upconversion spectrum. A Judd-Ofelt analysis was performed to calculate the radiative properties of Er 3+ :ZBLALiP microspheres, including the radiative transition probabilities, the electric dipole strengths, the branching ratios and the radiative lifetimes of the transitions involved. We have also identified the primary processes responsible for the generation of the observed wavelengths and have shown that this material has an improved range of emissions over other erbium doped fluoride glasses.
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TL;DR: In this paper, the authors used a technique called glancing angle deposition to grow nanocrystalline cuprous oxide thin films by annealing in air of copper films deposited firstly by this method onto glass substrates and characterized their structural, surface morphological, compositional, electrical and optical properties by using X-ray diffraction (XRD), scanning electron microscopy (SEM), electrical resistivity and optical (transmittance and reflectance) measurement techniques.
Abstract: When a thin film is deposited by physical vapour deposition, with the vapour flux arriving at an oblique angle from the substrate normal, and under conditions of sufficiently limited adatom mobility to create a columnar microstructure, the resulting structure is somewhat porous and grows at an angle inclined toward the vapour source. This technique called glancing angle deposition was used in this work to grow nanocrystalline cuprous oxide thin films by annealing in air of copper films deposited firstly by this method onto glass substrates. The films were characterized for their structural, surface morphological, compositional; electrical and optical properties by using X-ray diffraction (XRD), scanning electron microscopy (SEM), electrical resistivity and optical (transmittance and reflectance) measurement techniques. It was found that the above properties were strongly dependent on the obliquely angle deposition. The nanocrystallite size in these films was varied by varying the obliquely angle deposition. Optical studies show a direct allowed transition around in the range 1.5–1.85 eV for the annealed films. An enhancement in the oxidation process was observed for high obliquely angles deposition.
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TL;DR: In this paper, the moments of the dipoles are determined through a root mean squared procedure; this procedure fits the measured field to the theoretical field over a closed surface surrounding the device under test.
Abstract: The paper presents an efficient methodology to characterize electromagnetic disturbances radiated from power electronic devices. The approach is based on the substitution of an equivalent set of elemental magnetic dipoles for the real system; this set radiates the same near-field. The cartography of the magnetic field obtained with a measurement bench gives these dipoles. The moments of the dipoles are determined through a root mean squared procedure; this procedure fits the measured field to the theoretical field over a closed surface surrounding the device under test. The viability of the approach is demonstrated on two circuit boards. The first one is a canonical configuration involving two solenoidal inductors. The second one is a practical power electronic converter. Comparisons between numerical and experimental magnetic field distributions underline the ability of the equivalent model.
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TL;DR: In this paper, the structural, electronic and optical properties of two principal representatives of spinel oxides CdGa2O4 and CdIn 2O4 have been investigated using the full-potential augmented plane-wave plus local orbitals method within density functional theory.
Abstract: The structural, electronic and optical properties of two principal representatives of spinel oxides CdGa2O4 and CdIn2O4 have been investigated using the full-potential augmented plane-wave plus local orbitals method within density functional theory. We used the generalized gradient approximation (GGA) for the exchange-correlation (XC) potential. Moreover, the alternative form of GGA proposed by Engel and Vosko (GGA-EV) is also used for the band structure calculations. The equilibrium lattice constants and the internal parameters are in agreement with the available experimental results. Results obtained for band structure using GGA-EV show a significant improvement over other theoretical work and are closer to the experimental data. The pressure dependence of band gaps is investigated. The dielectric function, reflectivity spectra and refractive index are calculated up to 50 eV. Pressure and volume dependence of the static refractive index have been also calculated.
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TL;DR: In this paper, the authors synthesize a spin-coated TiO2 thin film using the solgel method and spin coating process, which shows the ratio of Ti:O ∼ 0.5, and diffusion of sodium ions from substrate into the layer, by increasing the calcination temperature.
Abstract: TiO2 thin films were synthesized by the sol-gel method and spin coating process. The calcination temperature was changed from 100 to 550 ◦ C. XRD patterns show increasing the content of polycrystalline anatase phase with increasing the calcination temperature. The AFM results indicate granular morphology of the films, which particle size changes from 22 to 166 nm by increasing the calcination temperature. The RBS, EDX and Raman spectroscopy of the films show the ratio of Ti:O ∼ 0.5, and diffusion of sodium ions from substrate into the layer, by increasing the calcination temperature. The UV-vis spectroscopy of the films indicates a red shift by increasing the calcination temperature. The contact angle meter experiment shows that superhydrophilicity of the films depends on the formation of anatase crystal structure and diffused sodium content from substrate to the layer. The best hydrophilicity property was observed at 450 ◦ C calcination temperature, where the film is converted to a superhydrophilic surface after 10 min under 2m W/cm 2 UV irradiation. Water droplet on TiO2 thin film on Si(111), Si(100), and quartz substrates is spread to smaller angles rather than glass and polycrystalline Si substrates under UV irradiation. PACS. 68.08.Bc Wetting - 73.21.Ac Multilayers - 82.30.Rs Hydrogen bonding, hydrophilic effects
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TL;DR: In this article, a transmission type of experiment was set-up to investigate coherent light scattering on suspensions with scattering centers having a wider size distribution, and the contrast, the average intensity and the average speckle size of the far interference field were calculated using an alternative simple algorithm that is presented in detail.
Abstract: A transmission type of experiment was set-up to investigate coherent light scattering on suspensions with scattering centers having a wider size distribution. For each sample the contrast, the average intensity and the average speckle size of the far interference field were calculated using an alternative simple algorithm that is presented in detail. The variation of the far field parameters with the scattering centers concentration is presented. A possible application in measuring the scattering centers concentration in the very small values range is suggested and the range is indicated.
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TL;DR: In this article, the phase stability of the microwave field interrogating the clock transition has been investigated and it has been shown that the frequency instability is limited by atomic shot-noise and therefore could be reduced were the atomic flux increased.
Abstract: The short-term stability of passive atomic frequency standards, especially in pulsed operation, is often limited by local oscillator noise via intermodulation effects. We present an experimental demonstration of the intermodulation effect on the frequency stability of a continuous atomic fountain clock where, under normal operating conditions, it is usually too small to observe. To achieve this, we deliberately degrade the phase stability of the microwave field interrogating the clock transition. We measure the frequency stability of the locked, commercial-grade local oscillator, for two modulation schemes of the microwave field: square-wave phase modulation and square-wave frequency modulation. We observe a degradation of the stability whose dependence with the modulation frequency reproduces the theoretical predictions for the intermodulation effect. In particular no observable degradation occurs when this frequency equals the Ramsey linewidth. Additionally we show that, without added phase noise, the frequency instability presently equal to 2×10 -13 at 1 s, is limited by atomic shot-noise and therefore could be reduced were the atomic flux increased.
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TL;DR: In this paper, the authors explore materials made of polymer-titanate composites for application towards the size reduction of high frequency electronic components, which may find use in microelectronic applications and in the miniaturization of circuit components (substrates, components, cavities, antennas etc.).
Abstract: The aim of this article is to explore materials made of polymer-titanate composites for application towards the size reduction of high frequency electronic components. A study has therefore been done on the dielectric effect of composites made of an epoxy matrix loaded with a mixture of barium titanate and calcium titanate. The effects have been quantified according to volume fraction of load. Results obtained from time domain reflectometry have been compared to modelling predictions from the generalized Lichtenecker law. Low frequency analysis (in the range DC — 500 MHz) has also been performed throughout this work, and it has primarily concentrated on conductivity behaviour which may be attributed to the effects of a percolation process. The study has confirmed the validity of the ternary mixture law being applied in order to predict the electromagnetic behaviour of the composite material. This material family may therefore find use in microelectronic applications and in the miniaturization of circuit components (substrates, components, cavities, antennas, etc.).
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TL;DR: In this paper, a new halosulphate phosphor NaMgSO 4 F:Ce 3+ and Na 3 SO 4 F :Ce3+ was synthesized by wet chemical method.
Abstract: A new halosulphate phosphor NaMgSO 4 F:Ce 3+ and Na 3 SO 4 F:Ce 3+ was synthesized by wet chemical method. The PL emission spectra of phosphors show strong Ce 3+ emission due to the transition of Ce 3+ ions. Ce 3+ emission in new halosulphates NaMgSO 4 F and Na 3 SO 4 F lattice may be useful for a scintillation application. XRD and photoluminescence (PL) characterization of phosphors has been reported in this paper.
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TL;DR: The TL glow curves of these halosulphate phosphors exposed to γ -rays for 5 Gy at the rate of 0.995 kGyh -1 are described and discussed first time here.
Abstract: Polycrystalline halosulphate phosphors are prepared by a wet chemical method. Strong thermoluminescence (TL) was observed in KZnSO 4 Cl, KMgSO 4 Cl, Na 3 SO 4 F and NaMgSO 4 F hosts. In these hosts Ce, Dy; Ce, Mn and Ce, Tb the Ce 3+ ions acting as sensitizers and Dy 3+ , Mn 2+ and Tb 3+ ions as activators. The TL glow curves of these halosulphate phosphors exposed to γ -rays for 5 Gy at the rate of 0.995 kGyh -1 are described and discussed first time here.
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TL;DR: In this article, the authors compared the efficiency in enhancing the Raman signal on a thin dye layer for metal-coated AFM tips as well as for electrochemically etched metal STM tips.
Abstract: In Tip-Enhanced Raman Spectroscopy (TERS) a metal (or metallized) sharp tip is used to enhance the electromagnetic field by a localized surface-plasmon excitation. Two different modes - atomic force mode (AFM) and scanning tunneling mode (STM) - together with their respective types of probe tips are used in TERS experiments. We have compared the efficiency in enhancing the Raman signal on a thin dye layer for metal-coated AFM tips as well as for electrochemically etched metal STM tips. A much higher enhancement factor and better reproducibility were found when using STM tips. The very different performance is mainly attributed to the more efficient plasmonic excitation when using bulk-metal tips and possibly to the morphological differences in the tip and apex shapes existing between the two tip types.