A study of single injection space-charge-limited current flow in insulator with two sets of traps distributed in energy is presented for a particular situation in which the energy separation of the two sets of traps is too small to give rise a current-voltage characteristic with maximum structure. The current-voltage characteristic is obtained in a simplified way with the help of regional approximation method. The obtained J-V characteristic is compared with previously reported experimental work on p-type GaSe sample. The comparison shows very good agreement between theoretical and experimental result, confirming the correctness of the analysis.

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.

Nano p-AgInTe2/n-CdS0.4Se0.6 heterojunction was constructed. The dark – current – voltage – characteristics of the prepared junction have been investigated in a temperature range from ~303 to 423 K. The operating conduction mechanism was found to be Pool-Frenkel emission for T > 323 K and V < +0.8 volt. The supposed band diagram of p-AgInTe2/n-CdS0.4Se0.6 heterojunction is exhibited. Analysis of the photovoltaic characteristic, at room temperature and under illumination of ~2.7 W/m2, lead to the determination of some solar cell parameters, such as; the short circuit current, the open circuit voltage, the fill factor and the power conversion efficiency.

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.

Single crystalline wurzite GaN nanorods are successfully synthesized on the tantalum catalyzed Si substrate by RF magnetron sputtering. The products are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectra (FTIR), transmission electron microscopy (TEM), selected-area electron diffraction (SAED) and photoluminescence (PL). The results show that the nanorods have a hexagonal wurtzite structure with diameters ranging from 80 to 200 nm and lengths typically up to 10 µm. The PL spectrum exhibits a strong UV light emission at 364 nm. The growth mechanism of the crystalline GaN nanorods is discussed briefly.

The band gap energies of zinc-blende InNx As1-x alloy as a function of its nitrogen composition have been calculated using the density functional theory. The results agree well with those obtained from experimental results. The minimum band gap energy of InNx As1-x alloy obtained is 70 meV at its N composition of 0.45. The band gap bowing coefficient of InNx As1-x alloy is obtained from the curve fitting of the simulated band gap energy versus the nitrogen composition, x. The band gap bowing coefficient of zinc-blende InNx As1-x alloy is found to be 2.072 ± 0.236 eV. The energy band gap for InN is also correctly predicted from this calculation.

Silver films have been grown by electrodeposition technique on sprayed ITO coated substrates under different conditions. The transmittance in the visible range have been enhanced by adding silver and the sheet resistance was reduced for films prepared under -0.4 V applied voltage during 200 s. The attachment of Ag particles onto ITO surfaces was strong enough for further use such as in opto-electronic devices and solar cells.

Amorphous Se70Te30–x Cdx (x = 0, 10) are obtained by thermal evaporation under vacuum of bulk materials on pyrographite and glass substrates. The I – V characteristic curves for the two film compositions are typical for a memory switch. They exhibited a transition from an ohmic region in the lower field followed by non-ohmic region in the high field region in the preswitching region, which has been explained by the Poole-Frenkel effect. The temperature dependence of current in the ohmic region is found to be of thermally activated process. The mean value of the threshold voltage $\bar{V}_{th}$ increases linearly with increasing film thickness in the thickness range (100–491 nm), while it decreases exponentially with increasing temperature in the temperature range (293–343 K) for both compositions. The results are explained in accordance with the electrothermal model for the switching process. The effect of Cd on these parameters is also investigated.

The paper presents a numerical simulation of the behaviour of SnO2:F/Si(N+)/Si(P) solar cells. The simulation addresses in particular the question of the role of the window layer SnO2:F for the device performance.As beginning step, the transparent conductive oxide of SnO2:F must be modelled in order to introduce its parameters in simulation codes. Two approaches were employed: one empirical by collecting the experimental data of spray deposited SnO2:F while the second one is theoretical by using models of highly degenerate wide band gap semiconductors.The second step consists in injecting the deduced parameters of fluorine doped tin oxide in simulation codes. We use two well-known photovoltaic simulation codes as PC1D and SCAPS 2.5. A comparative study of the results of structures SnO2:F/Si(N+)/Si(P) and Si(N+)/Si(P) have been done with a confirmation in enhancing the conversion efficiency by SnO2:F window layer addition.

The capacitance between any two arbitrary lattice sites of an infinite square network consisting of identical capacitors is studied analytically and numerically for a perturbed network. The perturbation is as a result of removing the bonds $(i_{0} j_{0})$ and $(k_{0} l_{0})$ from the perfect network. The equivalent capacitance is expressed in terms of the Lattice Green's Function (LGF) of the perturbed network. Solving Dyson's equation we express the LGF and the capacitance of the perturbed network in terms of those of the infinite perfect network. The asymptotic behavior of the perturbed capacitance is also studied. Finally, some numerical results are presented for the perturbed infinite square lattice, and a comparison is carried out for those of the perturbed and perfect infinite square network.

Based on the first-principles simulations, the oxygen vacancies in the ultrathin HfO2 layer as the gate dielectric in a metal-oxide-semiconductor structure is found to result in the conductionband offset alignment around the vacancy. Thus an increase in the gate leakage current tunneling current comes when the oxygen vacancies appear in the HfO2 layer wherever the oxygen vacancies locate. The relative increase in the tunneling current caused by the oxygen vacancies slightly change with the increasing oxide thickness for a low oxide electric field.

The characteristics of organic light-emitting devices based on tris-(8-hydroxyquinoline) aluminum (Alq3) with NaCl thin films inserted at both anode/organic and organic/cathode interfaces are investigated. We optimize the thicknesses of NaCl at both interfaces, and we get the optimal device with the structure of ITO/NaCl(2.0 nm)/N,N'-bis(1-naphthyl)-N,N'-diphenyl-1,1' biphenyl-4,4'-dimaine(NPB)/Alq3/NaCl(2.0 nm)/Al. The device shows much better electroluminescent (EL) performance than that of the as-stated standard device with only LiF buffer layer. The maximal current efficiency and power efficiency is improved by 31% and 67%, the turn-on voltage is also reduced from 4.2 V for the standard device to 3.1 V for our target device. This is due to enhanced electron injection and blocked hole injection, which results in more balanced hole and electron currents.

Copper-doped SrBi2Nb2O9 (SBN) thin films have been fabricated on fused quartz substrates at room temperature by RF magnetron sputtering technique. The chemical composition and Cu concentration in the deposited films were characterized by X-ray fluorescence spectrometer. XRD analysis indicated that the films have a single phase of layered perovskite structure and Cu doping in SBN films did not degrade their crystallinity at the dopant concentration of 9.5%. The nonlinear optical properties of the samples were determined using a single beam z-scan technique at a laser wavelength of 532 nm with laser duration of 25 ps. The results showed that the value of $\chi ^{(3)}$ of Cu-doped SBN films is about twice larger than that of the undoped, which is comparable with that of some representative nonlinear optical materials, indicating that metal-doping in dielectric is effective to enhance their nonlinear optical properties. This suggests that Cu-doped SBN films have great potential in designing nonlinear optical devices.

The present paper reports on the fabrication of In2O3 layers by oxidation of InN thin films deposited on n-type silicon substrate by magnetron reactive sputtering. The subsequent solar cells using the resulting In2O3/Si heterojunctions exhibit an ideality factor, deduced from current-voltage (I – V) characteristics of around 2.52 at a forward bias of 0.5 V. Other measured parameters were the short-circuit current (I sc ), the open-circuit voltage (V oc ), the maximum output power (P m ), the fill factor (FF) and the efficiency (η ), which had values of were 3.17 mA, 0.75 V, 0.869 mW, 0.365 and 9.66 %, respectively, under AM 1.5 illumination. The value of series resistance was around 107 Ω. In2O3 films formed by the oxidation of InN have a higher open-circuit voltage than In2O3-based solar cells formed by the oxidation of indium.

Superparamagnetic nanoparticles are very interesting objects having many applications among which MRI contrast agents are one of the more important. In this work the longitudinal relaxation times of Endorem and Lumirem, two colloidal solutions of iron oxide nanoparticles used as contrast agents for magnetic resonance imaging were measured at magnetic field intensities similar to the ones used in MRI. T 1 was seen to depend on nanoparticle concentrations as expected but, for the Lumirem, also on the time spend by the sample under the influence of the static magnetic field. The T 1 evolution was measured for colloidal solutions both different concentrations and different viscosities. The strange T 1 dependence is presented and discussed relating to the nanoparticles superparamagnetic properties. It is shown that one of the possible reasons for the fact is the formation of local field enhanced linear arrays of SPIO.

We report here on the elaboration and transport properties of assemblies of ZnO nanoparticles and nanorods synthesized by organometallic chemistry. Two different methods have been used to prepare the samples. The first one consists in the deposition of the nano-objects on the substrate (drop-casting method) whereas the second one consists in the direct synthesis of the nano-objects on the substrate (in situ method). All the samples were highly resistive in the dark. Conductivity of as-grown nanorods was light-sensitive whereas the one of as-grown nanoparticles was not. Annealing the nanoparticles at 200 °C increases their dark resistance and strongly decreases their resistance under light. We analyse the transient photoconductivity when the light is abruptly switched on and off. The increase of the current when the light is switched on is fast and follows a simple exponential function. Decrease of the current when the light is switched off is slower and can be described by a stretched exponential function for short times and by a power law at longer times. Our various experiments are discussed in the light of other experiments on ZnO nanorods and CdSe nanoparticles, and to available models describing transport in assemblies of semiconductor nanoparticles.

In2S3 thin films were deposited by flash evaporation of In2S3 powder. The effect of annealing in vacuum and under sulphur and oxygen atmosphere on the structural, compositional and optical properties of these films was investigated. X-ray diffraction studies reveal that the as-deposited films are amorphous. The formation of β-In2S3 phase is obtained after annealing under vacuum at 693 K or under sulphur pressure at a lower annealing temperature (573 K). The EDAX analysis reveals that the sulphurized films are nearly stoichiometric and those annealed in vacuum are sulphur deficient. Optical transmission spectra showed a slight shift of the absorption edge towards lower wavelengths. The optical gap value varied between 2.4 and 3 eV as a function of the film thickness, the annealing temperature and the atmosphere ambient.

The reconfiguration time of a holographic beam-shaping device using a liquidcrystal spatial light modulator (SLM) has been drastically decreased by fiveorders of magnitude to reach the microsecond range (~5 µs). Themethod involves an acousto-optic modulator (AOM) placed in front of the SLMwhich points the laser beam towards different pre-addressed regions of theliquid crystal plate. Because the addressing signal is not changed, thereconfiguration time is mainly governed by the AOM response time. Moreover,this method allows us to clean up the transient regime by suppressing the bleedeffect usually observed in the standard SLM reconfiguration.

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 2 mW/cm2 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.

OH- absorption bands of lithium tantalate crystals have been measured at room temperature, and the bands shape depending on the crystal composition has been observed. OH- absorption bands are fitted with three Lorentzian peaks by varying position, halfwidth, and area. Nearly constant peak positions (3461, 3475 and 3486 cm-1) for all samples are obtained. Hydrogenation is also performed to the crystals and its influence on the decomposed peaks (position, halfwidth and area) is investigated. The results show the fitting parameters of peaks have different values for crystals with different hydrogen concentration, which is interpreted by the different sites occupied by H+ in terms of the modified model about the location of Li-vacancy in the lattice. Additionally, it is shown that the halfwidth of peak at 3461 cm-1 remain unchanged regardless of hydrogen concentration, which make this parameter more suitable than other ones to determine the composition of LiTaO3 crystals. The quantitative relationship between the halfwidth of peak at 3461 cm-1 and the crystal composition is also presented.