In this paper, we report the experimental data of photoresponse namely; voltage responsivity and speed of response at λ = 904 nm of silicon photodiode formed by pulsed laser-induced diffusion technique. Experimental results demonstrated that the photodiode parameters strongly depend on the laser energy and substrate temperature. Maximum Responsivity obtained for p-n junctions photodetectors prepared by laser fluence of 9.17 J/cm2 for Al-doped Si and 10.03 J/cm2 for Sb-doped Si at substrate temperature (T s ) of 598 K. The pulse response waveform of photodetectors illustrated that the rise time is not dominated by RC. Non-linearity deviation coefficient was improved by factors 1.6 for and 2.7 for for Al-doped Si and Sb-doped Si photodetectors respectively when T s is raised from 300 K to 598 K.

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.

Crystallization processes of Se80Te20-x Cdx (x = 0, 4, 8, 10 and 12) alloys at different heating rates have been studied by differential scanning calorimeter (DSC) by using non-isothermal technique. The values of glass transition temperature (T g ) and crystallization temperature (T c ) are found to be composition and heating rate dependence. From the heating rate dependence of glass transition temperature and crystallization temperature, the activation energy of crystallization (ΔE c ), the activation energy for structural relaxation (ΔE t ) and the order parameter (n) have been calculated. It was observed that Se80Te16 Cd4 has a minimum value of activation energy of structural relaxation (ΔE t ), which indicates that this particular glass has a larger probability to jump to a state of lower configurational energy and higher stability in the glassy region.

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 Å and c = 3.160 Å. 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.

Si-doped and undoped GaAs1-x Nx layers are grown by molecular beam epitaxy (MBE) on GaAs(001) substrate with low nitrogen content. The Si-doped effect has been analyzed by photoluminescence (PL) measurements. At low laser power excitation the PL spectra of undoped layer are formed by GaAsN band level and several features attributed to the nitrogen localized states. For Si-doped layer, the GaAs1-x Nx Nx band level disappears and the large band attributed to the nitrogen localized states changes the form. At high laser power excitation, the PL spectrum is formed by only one peak corresponding to the most dominating nitrogen localized state. By comparing the doped and undoped layers, we note that the presence of silicon in the structure reduce the exciton bound energy to the nitrogen localized states.

We report the characterization of 1,8-naphthalene benzimidazole comprising carboxyl group. We have fabricated dye-sensitized nanocrystalline TiO2 solar cell (DSSC) based on naphthalene benzimidazole dye. The device structure is FTO/nc-TiO2/Dye/I–/I3 –/Pt/ FTO. We calculated the E HOMO and E LUMO levels of this new dye by using cyclic voltammetry measurement. The E LUMO level of naphthalene benzimidazole is 3.2 eV. This value is higher than the conduction band of TiO2. Electrons can be injected to the conduction band of TiO2. The current-voltage (I-V) characteristic of cell was measured under simulated AM 1.5 illumination (100 mW/cm2). We obtained the open circuit voltage; V oc = 0.344 V, short circuit current density; I sc = 5.93 mA cm-2, filling factor; FF = 0.45, power conversion efficiency; η = 0.91%.

Tilt growth is usually observed for the thin film growth on a substrate. Such tilt growth is considered as a consequence of the relaxation of the misfit strain between the epilayer and the substrate. In this paper, we propose a theoretical method to obtain the tilt angle of the epilayer, especially suitable for the heterostructure with large misfit strain which can be more than 10%. As an application of our method, we focus on two growth cases. One case is the growth of MnAs epilayer on GaAs (113) substrate with the lattice mismatch between the MnAs epilayer and the GaAs (113) substrate as high as 80%. And the other case is the growth of GaN epilayers on GaAs $\{1 \overline 1 l\}$ substrates. Results calculated from our method for the two cases agree well with the experimental observations. This method is general, and can be applied to other material systems with large lattice mismatch.

A method of dispersing nanogranules in a polymer by utilizing the stretching, compression, and shearing effects induced by bubble inflation in a polymer melt undergoing foaming is discussed. The bubble inflation is so fast, similar to the explosion of dynamite, that a complex composite stress field is exerted on the polymer melt around the inflating bubble. An expected dispersion effect of nanogranules in a polymer melt by bubble inflation has been shown by experiments. And a model, which we call In Situ Bubble Stretching (ISBS), is proposed. Comparison of a theoretical analysis of the dispersion effect is given by the ISBS method with the results from experimental scanning electron microscope micrographs given reasonable grounds for support of our hypothesis.

GaN nanowires were successfully synthesized on Si(111) substrates by ammoniating the Ga2O3/ZnO films at 900 °C. The structure, morphology and optical property of the as-prepared GaN nanowires were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), field-emission transmission electron microscope (FETEM), Fourier transform infrared spectrum (FTIR) and fluorescence spectrophotometer. The results show that the GaN nanowires have a hexagonal wurtzite structure with lengths of about several micrometers and diameters ranging from 30 nm to 120 nm. The representative photoluminescence spectrum at room temperature exhibited a strong emission peak at 374.1 nm and two weak emission peaks at 437.4 nm and 473.3 nm. Finally, the growth mechanism is also briefly discussed.

The influence of preparation conditions on the structure and optical properties of cadmium sulphide (CdS) thin films deposited on quartz substrates by means of the pulsed laser technique have been investigated. Oriented growth of hexagonal CdS nanoparticulate film with the C-axis perpendicular to the plane of the surface has been achieved up to a film thickness of 220 nm. The results indicate that the heat treatment played an important role on both crystal structure and optical properties. The grain size and the crystallinity of the films were increased, as well as the optical energy gap $E_{\it g}^{\it opt} $ (allowed direct transitions) was increased from 2.45 to 2.50 eV upon annealing. The dispersion of the refractive index of virgin and annealed films were estimated and explained using the Wemple-Didomenico (WD) single-oscillator model. The dispersion parameters and the free charge carrier concentrations were also estimated.

Microstructural and magnetic properties of 14N+ irradiated Co/Pd multilayers, deposited on ultra-flat large (2.5 in) glass substrates by a special hard disk industrial manufacturing system, are discussed. Upon irradiation with 14N+ ions at different energies (20–30 keV) and doses (1014–1015 ions/cm2), both the coercive and nucleation fields were found to change with respect to as deposited multilayer. Results indicate that the irradiation process leads to a lowering of the magnetic anisotropy due to the induced disorder and degradation of the interface quality: for an energy of 30 keV, at an irradiation level of 1015 ions/cm2, H c reduces from H c ≈ 5.4 kOe for the as deposited multilayer down to 300 Oe, being the easy axis still perpendicular to the multilayer plane; at the highest dose (1016 ions/cm2), the coercivity vanishes and the perpendicular anisotropy is suppressed.

This paper presents a method of heat-assisted magnetic probe recording, which could help increase the storage density in hard-disk data storage systems. The heating source is the field emission current from a scanning tunneling microscope (STM) tip. As perpendicular magnetic recording media, two types of CoNi/Pt multilayered films are used: one is strongly-coupled and the other is weakly-coupled granular medium. Recording marks were formed by local heating in the medium. The average mark size is 180 nm for the strongly-coupled medium, and 110 nm for the weakly-coupled one. Marks are arrayed in different formations with various spacings. With reduced spacing, the write probability of the recording system is reduced. The interaction between marks becomes stronger and in the strongly-coupled medium their position becomes disordered. By contrast, this does not happen for marks written in the granular medium. Based on this demonstration, we conclude that granular medium becomes a better candidate for ultra-high density recording.

A characterisation of a low pressure SF6 discharge was undertaken, by means of plasma diagnostics, including radiofrequency electrical probes, Langmuir probes and optical emission spectroscopy. Chemical kinetics modeling of the discharge was performed too. This was aimed to the understanding of a reported transition in the plasma induced surface modification on poly(ethylene terephthalate) (PET) fibres by SF6 plasma treatment which can be characterized as a striking wettability modification reverse displayed by plasma treated fibres as the SF6 pressure in the discharge exceeds a threshold value. Here we have investigated the modification also on different polymeric surface such as that of a PET film and of cellulose (paper). We point out that the observed transition could be understood as a switch between an increased surface hydrophilicity, induced by plasma treatment at low pressure, which produces also surface etching and activation, and an increased surface hydrophobicity, imparted by plasma treatment at higher pressures, due to extended surface fluorination.

Perfluorocyclobutane (c-C4F8) is one of the most promising gases to be used in gas mixtures, which are the candidates to substitute for SF6 gas as high dielectric strength insulators with a reduced potential for global warming. The set of initial collision cross-sections are assembled and modified. The motion of electrons in c-C4F8 in uniform electric fields is simulated using Monte Carlo method. Also the density-normalized ionization coefficients α/N, attachment coefficients η/N, the effective ionization coefficients (α – η)/N, drift velocity (V e ) and the electron longitudinal diffusion coefficient (ND L ) are calculated for the range of density-reduced electric field strength, 300 $\leqslant$ E/N $\leqslant$ 1000 Td. The electron swarm parameters of simulation are compared with experimental data and other results of simulation, which obtain a good agreement. However, further calculations and measurements for c-C4F8, such as η/N and ND L are required.

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.

This paper deals with the new results of the distributed point source method (DPSM). This method has been first developed at the SATIE lab, located at the École Normale Supérieure of Cachan, France. This method now allows the modelling of interactions between an incident wave and an obstacle. It can be applied in the non destructive testing area, using eddy currents or ultrasonic waves.

We present a numerical model used to compute steady flow solutions of the venous circulation of the leg. The network topology is based on clinical data and the flow is assumed to be steady, incompressible, and one-dimensional. We develop a non Newtonian approach to a one-dimensional flow because the blood viscosity depends on the velocity profile, and we demonstrate theoretically the pertinence of a phenomenological law of equivalent viscosity. Clinical experiments observe hemodynamical variables (i.e. venous pressure, venous area, blood velocity) only at the accessible places. In contrast the numerical model results are not limited to particular locations but can be evaluated on every point of the network. It provides important help to the definition of a clinical protocol. The model was designed to quantify a compression level of elastic compression stockings and to plan clinical studies. We validate the numerical approach using a published clinical trial, where the diameter of superficial and deep veins were measured at different compression pressures. We show also that the viscosity variations in a bed-rest position as a consequence of the application of a European Class II compression stockings. These variations could prevent the hyper-coagulability and the stasis of the blood.