An efficient technique for determining the small-signal equivalent-circuit model of a Metal collector-up Heterojunction Bipolar Transistor (C-up MHBT) is presented. The technique employs analytically derived expressions for direct calculation of HBT T-Model equivalent circuit element values in terms of the measured S-parameters. This approach avoids errors due to uncertainty in fitting to large, over determined equivalent circuits and does not require the use of test structures and extra measurement steps to evaluate parasitics. Physically realistic results are demonstrated under various biasing conditions for the n-p-n InP/InGaAs HBT with metallic collector up structure. The agreement between the measured and model-produced data is excellent over the large frequency range and for several polarizations conditions for devices.

P-type Sb2−x Bix Te3 crystals with various chemical compositions (x = 0.40, 0.44, 0.47, 0.50, 0.53, 0.56 and 0.60) were fabricated by zone melting method. Transmission electron microscopy and energy dispersive X-ray microanalysis were performed to characterize the evolutions of defects on the sites of Bi, Te and Sb atoms in the lattice. Study of Sb2−x Bix Te3 structure reveals the formation of Bi2Te3 in which native defects are a consequence of overstoichiometry of Bi atoms in Bi2Te3 single crystal. Thermoelectric properties, including Seebeck coefficient (α), electrical conductivity (σ), thermal conductivity (k), and Hall constant were measured at room temperature. In terms of thermoelectric properties, increasing Bi2Te3 content (x) decreased carrier (hole) concentration (and σ, as a result) and increased α. The maximum figure-of-merit (Z = α2σ/k) of 2.7×10−3 K−1 was obtained at about 300 K for 25%Bi2Te3 − 75%Sb2Te3 with 3 wt% excess Te recommended for thermoelectric properties modification. Added Te is considered not only as a dopant, but also to compensate the deficiency of Tellurium understoichiometry. The results compared with reports of several authors to evaluate the dependency of parameters on sites of the atoms. The novelty of this work is to present the sites of the atoms in the lattice of the ternary compounds and the effect of defects occurred due to the atomic sizes of the Bi, Sb and Te.

In2S3 thin films containing different quantities of sodium have been synthesized by co-evaporation of sodium and In2S3 powder from separate sources using vacuum thermal evaporation method. Films were deposited on ordinary glass at 240 °C. The process of incorporation of sodium was studied as function of at.% Na. Films have been characterised by means of X-ray diffraction, SEM, EDAX and spectrophotometry. X-ray diffraction analysis confirmed the initial amorphous nature of deposited layers and revealed the formation of In2S3 as function of annealing layers containing sodium in nitrogen at 300 °C for 2 h. Energy Dispersive X-ray Analysis (EDAX) revealed the composition of the films as a function of the sodium incorporation. Surface Electron Microscopy showed that these films were granular and homogenous. The films have an n-type electrical conductivity and their optical direct band gap can be managed between 2.20 and 2.45 eV by controlling their sodium content. The variation of parameters for as-deposited and annealed films has been studied within $x\le 4$ at.% solid solution composition. Thin layers with homogeneous surfaces, direct band gap energy $(E_g)$ of about 2.45 eV for 4 at.% Na and 0.9 μm-thick have been achieved.

Recently, research has been concentrated on the study of the magnetic nanoparticules for their use in the design of magneto-optical devices. The magneto-optical waveguides for example exploitthe Faraday effect to obtain a rotation of polarization TE and TM independent of the propagation direction. In this work, we study isolating component whose operating principle is based on the minimization of the phase mismatch between TE and TM fundamental propagation modes.It appeared promising to use as a guiding film the thin layers doped bymagnetic nanoparticules γ-Fe2O3 in order to carry out an adequate phase mismatch. This last can be adjusted by permanent linear birefringence resulting from the application of an external magnetic field during the gelation of the solution which constitutes the guiding film. Many studies were undertaken primarily to minimize the birefringence between TE and TM modes, for that this work represents a new potential means to reach the phase matching by acting on the anisotropy and the thin layer thickness.This condition can be realized in the waveguides with SiO2/TiO2 guiding thin layer doped by nanoparticules of maghemite γ-Fe2O3. The simulations carried out by the FMM method and MATLAB allowed to deduce the conditions to decrease the phase mismatch and increase the conversion ratio of TE/TM modes in order to ameliorate the isolation.

Low pressure Plasma Enhanced Chemical Vapour Deposition is commonly used to deposit insulators on temperature sensitive substrates. In these processes, the ion bombardment experienced by films during its growth is known to have benefits but also some disadvantages on material properties. In the present paper, we investigate the influence of this bombardment on the structure and the electrical properties of SiO2-like film deposited from oxygen/hexamethyldisiloxane radiofrequency plasma in continuous and pulsed modes. First, we studied the ion kinetics thanks to time-resolved measurements by Langmuir probe. After, we showed the ion bombardment in such plasma controls the OH bond content in deposited films. Finally, we highlight the impressive reduction of fixed charge and interface state densities in films obtained in pulsed mode due to a lower ion bombardment.

Thermal evaporation technique has been employed to grow silver phthalocyanine nanostructures on glass substrates kept at different substrate temperature in vacuum of 10−5 Torr. These samples have been studied for their structural and optical properties. TEM investigations show the formation of long nanowires in AgPc thin films prepared at substrate temperature of 298 and 303 K, whereas films prepared at 308 K show the formation of nanobelts. XRD observations reveal that silver phthalocyanine nanowires are crystalline in nature. The significant blue shift in the UV-VIS absorption spectra of the silver phthalocyanine nanowires in comparison to bulk sample, indicate of effect of quantum confinement.

Pd/SnO2 composite films were obtained by wet chemical route using SnCl2:2H2O as tin containing precursor and PdCl2 as palladium containing precursor. The bilayer structures were subjected to rapid thermal annealing for the incorporation of Pd in SnO2 matrix. Pd/Sn was varied between 6 to 20% for optimizing the Pd concentration for improved sensitivity. Liquid Petroleum Gas (LPG) sensing properties were also investigated. The films thus obtained were subjected optical, microstructural, FTIR and Raman studies both before and after LPG exposure.

A complete PECVD process for the plasma polymerization of miniature proton exchange membranes (PEM) is presented. Styrene and trifluoromethane sulfonic acid are used as plasmagen precursors in a capacitive coupled low pressure discharge. The process is monitored by impedance probe measurements to ensure stability and reproducibility. FTIR analyses show that such membranes are mainly made up of a polystyrene-like matrix with grafted sulfonic acid groups, which proportion is tuneable as a function of the plasma parameters. The best results in term of deposition rate, monomer structure retention and PEM performances are obtained under pulsed plasma conditions, enhancing radical processes compared to continuous plasma. Because of their thinness and cross-linked structure, such membranes exhibit a similar proton conduction ability and a methanol permeability reduced by a factor 150 compared to Nafion $^{\circledR}$ . SEM observations show a good compatibility of plasma polymerized membranes whatever the substrate is. Consequently, PECVD process enables their better integration in micro fuel cells compared to conventional spin coating method.

In this present communication, we have studied the effect of hot-carrier degradation effects on surface potential, threshold voltage and DIBL of the sub-micron device. We have derived a more accurate model for the threshold voltage in the presence of hot carrier degradation effect. Our model includes a fitting parameter to take care of short channel effects. The validity of our model is verified by the MINIMOS simulator results. Our analysis predicts that the minimum potential position along the channel is not affected by the sign of the hot carrier induced localized interface charge density and always occurs in damage free region. DIBL effect is more pronounced in submicron devices in the presence of the hot carrier degradation effect.

Microplasmas refer to electric discharges created in very small geometries able to operate in DC mode at high pressure without glow to arc transition. The recent and considerable interest in microplasmas is due to their unique properties in term of discharge stability and power loading. A microplasma configuration which has proven to be stable at atmospheric pressure and up to a power density of some 100 kW/cm3 is the Micro Hollow Cathode Discharge (MHCD) developed by Schoenbach and coworkers. MHCDs are created by applying a voltage between two closely spaced hollow electrodes separated by a dielectric layer. The thickness of the dielectric and the diameter of the hole are both on the order of some 100's microns. These MHCDs can be used as plasma cathodes for generating a diffuse discharge between the MHCD cathode and a third positively-biased electrode placed some distance away. This is the so-called Micro Cathode Sustained Discharge (MCSD) configuration, which can be operated as a non self-sustained discharge. In that mode, the MCSD appears as a unique tool for producing, at high pressure, large fluxes of O2(a 1 Δ g ) metastable states which cannot be efficiently produced in classical self-sustained discharges. Based on experimental works performed by our group and on modeling studies done by Pitchford and coworkers at Toulouse University, this paper summarizes the properties of the plasmas generated by the MHCD and the MCSD, with an emphasis on the new fascinating opportunities for the production of O2(a 1 Δ g ) metastable states by electrical discharges in high pressure rare gas-oxygen mixtures.

A 3D modelling is used to obtain the expression of excess minority carrier density in base region of a polycrystalline silicon solar cell. The concept of the junction recombination velocity Sf is used to quantify how excess carrier flow through the junction in actual operating conditions. The plot of the photocurrent density allowed study the influence of the grain boundary recombination velocity and grain size on both, the junction recombination velocity and on the back surface recombination velocity of an n +-p-p + solar cell. This study pointed out the importance of the losses at the back side of solar cell. It's also show that the junction recombination velocity is more important for small grain size with large values of grain boundary recombination velocity.

Hybrid materials composed of polyhedral oligomeric silsesquioxanes (POSS) and a polyphenylene vinylene (PPV) derivative were fabricated and characterized by optical and surface spectroscopy. The hybrid thin films have similar optical properties as the pristine polymer but contributions of the POSS are evidenced in infrared spectroscopy. Organic light emitting diodes using the hybrid material as an emitter clearly showed an improvement of the electrical characteristics and the efficiency of the devices as compared to those using the pristine polymer. The effects of POSS incorporation to the polymer are discussed via the obtained results.

Ba0.65Sr0.35TiO3 (BST) thin films have been deposited by radio frequency magnetron sputtering. The effects of the deposition parameters on the crystallization and microstructure of BST thin films were investigated by X-ray diffraction and field emission scanning electron microscopy, respectively. The crystallization behaviour of the films is clearly affected by the substrate temperature, annealing temperature, and sputtering pressure. The thin films that are deposited at room temperature are amorphous in their as-deposited state. However, an improved crystallization can be observed for BST thin films deposited at higher temperatures. As the annealing temperature is increased, the dominant X-ray diffraction peaks become sharper and more intense. The dominant diffraction peaks increase with sputtering pressure, steadily increasing for films deposited from 0.37 to 1.2 Pa. When the sputtering pressure is increased up to 3.9 Pa, the films have a (110) + (200) preferred orientation. Possible correlations between the crystallization and the changes in the sputtering pressure are discussed. SEM measurements indicate that the films, which consist of small grains, are smooth and that the interface between the film and the substrate is sharp and clear.

Recently, the bactericidal efficiency of a low-pressure plasma process using a pure N2 flowing post discharge was demonstrated [Eur. Phys. J. Appl. Phys. 34, 143 (2006)]. In order to use this process for the decontamination of medical fiberscopes and endoscopes and more generally for the industrial decontamination of hollow bodies, the ability of the nitrogen atoms (which are believed to be the main decontamination agent) to flow in low diameter tubes (between 2 and 8 mm i.d.) without massive destruction is checked. The dependence of the N-atom concentration with the length, the internal diameter and the material of the tubes is studied and quantified. It is shown that the N-atom concentrations measured at the outlet of a polyamide tube of 6 m in length and of a 0.2 m long stainless steel tube are sufficient enough to provide high inactivation levels.

A novel approach for determination of refractive index dispersion n(λ) and thickness d of thin films of negligible absorption and weak dispersion is proposed. The calculation procedure is based on determination of the phase thickness of the film in the spectral region of measured transmittance data. All points of measured spectra are included in the calculations. Barium titanate and titanium oxide thin films are investigated and their n(λ) and d are calculated. The approach is validated using Swanepoel's method and it is found to be applicable for relatively thinner films when measured transmittance spectra have one minimum and one maximum only.

In this work, we study the optical interband transitions of InP on silicon (InP/Si) and on porous silicon (InP/PSi) substrates grown by molecular beam epitaxy (MBE). Spectroscopic ellipsometry for photon energies from 2 to 5 eV is used to determine the InP/Si and InP/PSi complex refractive index and thickness. Bruggeman effective medium approximation (EMA) associated to the Cauchy model are used to model the experimental ellipsometric data. We have found that the E 1 and E 1 + $\Delta _{1}$ transition energies of InP/Si and InP/PSi shift to low energies compared to bulk InP. This effect is interpreted as a result of the strain relaxation of the InP layers grown respectively on Si and porous Si substrates.

The ion swarm data such as reduced mobilities, diffusion coefficients and reaction rates of N4 + in N2, O2 and dry air (80% N2, 20% O2) have been determined from a Monte Carlo simulation using calculated and measured elastic and inelastic cross sections. The elastic cross sections used have been determined from a semi-classical JWKB approximation based on a rigid core potential model. The inelastic cross section of N4 + in N2 has been deduced from the measured experimental rates whereas for N4 + in O2 the measured inelastic cross sections have been extended to low and high energies by appropriate approximations. Then the cross sections sets have been validated from comparison of calculated and measured ion swarm data. From the cross sections sets obtained in pure N2 and O2, the ion swarm data for N4 + in dry air are then calculated for a large E/N range [1–104]Td. Finally, the influence of N4 + ions on the streamer development was analyzed with a 2D fluid model in the case of dry air at atmospheric pressure for a point-to-plane electrode configuration.

This work is an assessment of recent developments on microwave plasmas at atmospheric pressure and their applications in the field of surface treatment. A special attention is paid to the question of the accuracy of data at high temperature (above 2000 K) and to the non-locality of the energy dissipation in argon and helium plasmas.

This paper presents a unified thermal model, which can describe thethermophysical effects with laser pulse width ranges from nanosecondto femtosecond. Take gold target as an example, the numericalsolutions are obtained from the unified model using a finitedifference method. The temperature distribution of the electron andthe lattice along with space and time at a certain laser fluence ispresented. The time-dependence of lattice and electron temperatureon the surface for different laser fluence is also performed. Thesatisfactory agreement between our numerical results andexperimental results of vaporization threshold indicates that theunified thermal model is correct and reasonable.