Thin films of antimony-doped tin oxide (ATO) have been prepared by the sol-gel dip-coating (SGDC) process, using tin(II) chloride dehydrate (SnCl2, 2H2O) and antimony (III) chloride (SbCl3) as host and dopant precursors respectively. The effect of antimony doping on the structural, thermal, electrical and optical properties of the samples were investigated. The structure of the (ATO) powders was analysed by X-ray diffraction (XRD) and the microstructure of the thin films by scanning electron microscopy (SEM). It was clear from these investigations that its structure is tetragonal rutile type and that an increase in Sb-doping decreases the crystallite size of the (ATO) particles. Thermal analysis by differential scanning calorimetry (DSC) showed that the crystallization temperature is about 370 °C whatever the Sb-doping amount. The lowest resistivity (2.6 × 10−3 ${\rm \Omega}$ cm) was obtained for the 5% Sb-doped film and the value of the band gap (3.69 eV) for the undoped film, increases slightly with Sb-doping increasing for the doped films.

Voltage characteristics of polysilicon thin films transistors (Poly-Si TFTs) are related to basic material and device parameters. Understanding and modeling the electrical behavior of poly-Si TFT require knowledge of equivalent properties of polysilicon which are strongly affected by defects present in this material. A numerical analysis, which studies the electrical characteristics of small-grains poly-Si TFTs, has been investigated. The density of states (DOS) in the band gap is modeled by assuming an exponential distribution of deep and tail states. The proposed model evaluates the influence of both deep and tail states on the electrical conduction process and the dominant contribution of tail states on the threshold voltage values while the deep states in the middle of polysilicon gap controls the lower threshold regime. The surface potential and ON/OFF current ratio are also calculated. The comparison of the generated current-voltage characteristics obtained from numerical simulation TCAD-ATLAS with those reported in the literature show a good agreement.

In this paper the remote surface roughness effects on channel electron density of nano MOSFET is discussed by solving the coupled Schrödinger equation and Poisson equation. The results demonstrate that the remote surface roughness could largely affect the density of inversion channel electron, and the change of electron density by this effect has been found to have approximately linear relationship to the remote surface roughness. This implies that the mobility degradation effect by remote surface roughness scattering can be partially erased for the on-state current.

The as-prepared samples of Sn10Sb20Se $_{70-X}$ TeX chalcogenide system were amorphous as evidenced by X-ray diffraction and Differential scanning calorimetry studies. The different crystalline phases emerged in annealed Sn10Sb20Se $_{70-X}$ TeX samples have been identified. Glass transition temperature T g of the as-prepared samples decreases sharply with tellurium substitution upto 2 at% and then it starts increasing upto 10 at% and decreases again on further substitution of tellurium. The change in glass transition temperature T g has been explained based on bond formation energy of different heteropolar bonds and crystalline phases obtained in the annealed samples with different tellurium contents.

We report on microstructures of HfAl2O5 gate dielectric film grown on Si substrate with a Ti capping layer treated with rapid thermal annealing process. X-ray reflectivity, atomic force microscopy and X-ray photoelectron spectroscopy are used to investigate the sample. Results show that a Six (SiO $_{2})_{(1-x)}$ layer naturally forms at the interface between the HfAlO layer and the Si substrate in the as-grown sample. With the help of the Ti capping layer on the HfAlO/Si, the annealing treatment can effectively remove the Six (SiO $_{2})_{(1-x)}$ interface layer, which enhances the capacitance of the dielectric film. On the other side, the annealing process roughens the interfaces of the sample, which brings into the increase of the leakage current. Higher temperature of the annealing treatment results in rougher interfaces. Thus, the annealing temperature should be chosen properly to improve the capacitance of the film, before the interface roughening works to increase the leakage current. In this way, the dielectric and structural properties of the samples can be optimized.

Electrical properties ofSnO2-Co3O4-Nb2O5-Cr2O3 ceramicssintered at 1100−1400 °C were studied. Materials exhibitknown varistor properties (superlinear and symmetric current-voltagecharacteristic) only if sintered at relatively high temperatures of1300−1400 °C. In ceramics sintered at 1100−1200 °C,the current limiting effect (current is saturated and even decreasedwith voltage increase) and its transformation into the varistoreffect were found. It was ascertained that the capacitance ofsamples is decreased with increasing frequency more sharply forceramics sintered at 1100−1200 °C than at1300−1400 °C. The low-frequency capacitance and acconductance of ceramics sintered at 1100−1200 °C wereincreased and showed further strong decrease with electric field.The results of electrical measurements are discussed in terms of thebarrier model.

A modified and improved low frequency model for polycrystalline silicon thin-film transistors (poly-Si TFTs) is developed in this paper. For small grain size poly-Si TFTs, based on carrier number fluctuations, an improvement of the standard low frequency noise model has been investigated to explain the noise characteristics of poly-Si TFTs. An exponential energy distribution for interface density of states is employed to model the interface trap capacitance. For large grain size devices, mobility fluctuations related to fluctuations of the grain boundary charges is used to describe the excess subthreshold noise. The anomalous noise increase behavior of poly-Si TFTs when operated in the kink regime is also studied and modeled. The proposed model and the experimental data agree well over a wide range of operation regimes.

For industrial applications, microwave heating is an important technique. However, the homogenizationproblem must be taken into account to obtain rapid and reliable processes. Some industrialmicrowave heating systems are complex and expensive. In this paper, we propose a simple techniquewhich use a cavity excited by a linear or a circular electric field polarization. A better microwaveheating homogenization is obtain on ferrite and ethanol samples when the circular polarizationis used. A specific test bench was made to perform temperature measurements on several samplepoints.

In this paper, we first fabricate and demonstrate the InGaP/GaAs camel-like gate field-effect transistor with InGaAs pseudomorphic heavy-doped channel. Due to the large gate potential barrier for the use of the n+-GaAs/p+-InGaP/n-GaAs camel-like gate and the thin as well as heavy doping n+-InGaAs channel layer, the effective conduction band discontinuity $(\Delta E_c)$ is substantially extended and a high gate turn-on voltage up to 2.0 V is obtained. The device exhibits a relatively broad gate voltage swing resulting from the high gate turn-on voltage. In addition, a maximum drain current of 393 mA/mm and a maximum transconductance of 96 mS/mm are measured. These results indicate that the studied device is suitable for signal amplifier and linear circuit applications.

Thin Films of Azo Dye (1-Phenylazo-2-Naphthol) have been prepared by thermal evaporation technique onto quartz substrates held at about 300 K during the deposition process with different thicknesses range 625–880 nm. X-ray diffraction and the differential thermal analysis showed that the Azo Dye sample is crystalline nature and thermal stable in temperature range from room temperature to 100  $^{\circ}$ C. The optical constants (the refractive index n, the absorption index k and the absorption coefficient α) were calculated for Azo Dye (1-Phenylazo-2-Naphthol) thin films by using spectrophotometer measurements of the transmittance and reflectance at normal incidence in the spectral range 400–2200 nm. The obtained values of both n and k were found to be independent of the film thicknesses. The refractive index has anomalous behavior in the wavelength range 400–1000 nm besides a high energy transition at 2.385 eV. The optical parameters (the dispersion energy E d , the oscillation energy E o , the room temperature optical dielectric constant $\varepsilon_{l}$ , the lattice dielectric constant $\varepsilon_{L}$ , the high frequency dielectric constant $\varepsilon_{\infty}$ and the ratio of carrier concentration to the effective mass $N/m^{\ast}$ ) were calculated. The allowed optical transition responsible for optical absorption was found to be direct transition with optical energy gap of 1.5 eV for Azo Dye sample. The band tail obeys Urbach's empirical relation. 

Silicon carbide junction field effect transistor (SiC-JFETs) is a mature power switch newly applied in several industrial applications. SiC-JFETs are often simulated by Spice model in order to predict their electrical behaviour. Although such a model provides sufficient accuracy for some applications, this paper shows that it presents serious shortcomings in terms of the neglect of the body diode model, among many others in circuit model topology. Simulation correction is then mandatory and a new model should be proposed. Moreover, this paper gives an enhanced model based on experimental dc and ac data. New devices are added to the conventional circuit model giving accurate static and dynamic behaviour, an effect not accounted in the Spice model. The improved model is implemented into VHDL-AMS language and steady-state dynamic and transient responses are simulated for many SiC-VJFETs samples. Very simple and reliable optimization algorithm based on the optimization of a cost function is proposed to extract the JFET model parameters. The obtained parameters are verified by comparing errors between simulations results and experimental data.

Photoinduced reversible switching of charge carrier mobility in conjugated polymers was studied by theoretical and experimental methods. The quantum chemical calculations showed that the presence of dipolar species in the vicinity of a polymer chain modifies the on-chain site energies and consequently increases the width of the distribution of hopping transport states. The influence of photoswitchable charge carrier traps on charge transport was evaluated by current-voltage measurement and by impedance spectroscopy method. It was found that deep traps switchable by photochromic reaction may significantly control the transport of charge carriers, which is exemplified as a significant decrease of the current and increase of parallel resistance measured by impedance spectroscopy.

Plant fibers with nonzero microfibril angle show no plane reflection symmetries, the groups of spatial symmetry transformations consisting of rotations only. The spatial point symmetry group of any material made of such fibers is of order which is half of the order of the symmetry group of the corresponding orthotropic material. However, materials consisting of fibers show similar degeneracies of stiffness eigenvalues as the non-fibrous materials. Stiffness degeneracies appear to be controlled by the integer exponents of dicycle conditions applied on products of vectors generating symmetry groups. It is found that flat orthotropic sheets always retain their planar shape in eigen deformations, whereas those made of fibers with microfibrils do not. Features of the out-of-plane deformations are clarified. Orthotropic material elements experience normal on-axis eigen strains only, whereas fibrous bodies with orthotropic fiber alignment may experience on-axis shear strains as eigen strains.

Note to the reader:

On page 10402-p12, four mistakes have been corrected on September 7, 2009:

The following commands: " $\backslash$ overline{pq}" ( $\overline{pq}$ ) and " $\backslash$ overline{number}" have been replaced respectively by " $\backslash$ overline{p} $\backslash$ overline{q}" ( $\overline{p}$ $\overline{q}$ ) and " $\backslash$ overline{number} $\backslash$ overline{number}".

Thin film organic field-effect transistors were grown with vapor-deposited polycrystalline-octithiophene on silicon oxide insulating layers. This component requires an ohmic source and drain contacts for ideal operation. The performance of organic electronic-devices is often limited by injection. In many real situations, however and specifically in organic devices, the injection of charge carriers from metals into semiconductors is non-linear. This has an adverse impact on the performance of thin film transistors, and makes the analysis of electrical measurements a complex task because contact effects need to be disentangled from transistor properties. This paper deals with the effects of non-ohmic contacts on the modeling of organic transistors and gives specific rules on how to extract the real transistor parameters using only electrical measurements. Several methods are used in order to study the influence of the contact resistance on the performance of organic transistors. This influence appears especially on the current-voltage characteristics of organic field effect transistor. We present a first method used to extract the key parameters of OFET such as; mobility, threshold voltage and contact resistances using the fit of the transfer characteristic of the devices. The second method has been used to exploit the different functional dependences of current on gate voltage which is induced by the presence of contact resistances in the linear and in the saturation regimes. All electrical key parameters of OFETs based on octithiophene have been extracted and we demonstrate that both mobility and contact resistance depend on gate voltage and temperature.

Optical properties of 4-tricyanovinyl-N, N-diethylaniline thin films were investigated using spectrophotometric measurement of transmittance and reflectance at normal incidence of light in the wavelength range of 200–2500 nm. The optical constants (refractive index, n, and absorption index, k) were calculated using a computer program based on Murmann's exact equations. The calculated optical constants are independent of the film thickness and their values are decreased by annealing temperature. The optical dispersion parameters have been analysed by single oscillator model. The type of transition in as-deposited films is indirect allowed with a value of energy gap equals to 1.45 eV, which increased to 1.51 eV upon annealing.

3-aminophenol, an organic nonlinear optical material for frequency conversion was prepared by crystallization from aqueous solution XRD pattern reveals that the grown crystal belongs to orthorhombic system having non-centrosymmetric space group of P21ab. Functional groups are identified by analyzing the vibrational spectrum. Decomposition mechanism and melting point of the title compound were found using thermal measurements. The range and percentage of transmittance is determined by recording UV-VIS spectrum. The photoluminescence spectrum explains the transition mechanism of ions. Charge transfer π-electron chromophores are characterized by molecular first hyperpolarizability (second order optical non-linearity) values approaching 1.5509 × 10−30 esu for the title compound, which is nearly 5.3 times greater than that of urea. The hybrid Hartree-Fock exchange-correlation functional is used in conjugation with 3–21 G (d) basis set for hyperpolarizibility calculations. Nonlinear optical (NLO) study using Kurtz and Perry technique have been carried out to confirm the preliminary SHG property. Dielectric measurement was also performed to study the distribution of charges within the crystal. The mechanical strength of crystal is calculated.

We present the successful recrystallization of Bechgaard salts with the microwire shape using the drop casting method. The samples are deposited on a substrate with previously prepared patterns made by optical lithography. The physical properties of the microwires are shown. The excellent transport properties show that this technique provides a new method for the tuning of the physical properties of molecular conductors and the first step toward applications. The pressure effects of the substrate on the conduction are discussed.

The ZnSx Se $_{1-x}$ (0 ≤x≤ 1) films were deposited on soda lime glass substrates by thermal evaporation technique. Optical and structural properties of these films were compared with the ZnSx Se $_{1-x}$ films deposited by various other techniques. XRD measurement showed that ZnSx Se $_{1-x}$ films are polycrystalline in nature with the preferred orientation along [111]. It was observed that the lattice constant decreases and the optical energy band gap increases with the sulfur content of the film. These results are in good agreement with the properties of ZnSx Se $_{1-x}$ films deposited by various other methods. Additionally, it was observed that the refractive index of a ZnSx Se $_{1-x}$ film decreases with increasing sulfur content. The results reported in this paper suggest that the lattice constants, optical energy band gap and refractive index of ZnSx Se $_{1-x}$ film can be tailored for a specific application by selecting suitable value of x.

V2O5 thin films were prepared by the sol-gel spin coating process. The Li+ ions insertion effect on optical and electrochromic properties of those films was studied. The diffusion coefficient was calculated using both cyclic voltammograms and chronoamperometric curves. The amount x of Li+ ions in Lix V2O5 was also calculated. Finally, the electrochromic performance evolution characteristics such as the reversibility, coloration efficiency, coloration memory stability and response time were studied.

Transient and steady state currents in polyethylene, under low and high dcvoltages, are studied. In fact, a bipolar transport physical model is developed in order to characterize the space charge dynamics within an additive-free polyethylene film, under trapping and recombination mechanisms. The numerical computational models, used for the bipolar transport of carriers, are applied to the Poisson's, the continuity and the transport equations with the appropriate physical conditions. The principal and the new numerical results are calculated especially when high dcvoltages are applied. Indeed, the net charge density numerical profiles show the appearance of the space charge packets that are revealed for the first time in numerical modelling although they have long been reported in experimental works. These space charge packets induce some new aspects on the external transient current evolutions, produce the oscillations of the conduction and the displacement current before the steady state, and generate a conduction regime that is dominated by the interface electrode-insulator. These numerical results are consistent with those reported in some experimental works. However, under low dc voltage the space charge packets disappear and the space charge limited current aspect appears on the external current profile.