We have theoretically investigated the intersubband transition for different doping concentrations and thickness in Si δ-doped GaAs with an applied electric field. The electronic properties such as the δ-potential profile and the subband energy have been calculated by solving the Schrödinger and Poisson equations self-consistently. We show an abrupt drop of the energy differences and the absorption peaks whenever the external electric field reaches a certain value. We can say that the appearance of a second quantum well in the effective potential dependent on the applied electric field creates a rapid change in the subband energies. This critical electric field value changes as dependent on the donor concentration and thickness. Thus, we conclude that the intersubband optical absorption is very sensitive to the donor distribution and thickness as dependent on the applied electric field. This changing in the intersubband transition gives a new degree of freedom in regions of interest semiconductor device applications.

Results of a quantitative characterisation SIMS at high levels of boron-doping concentration (2 × 1020 cm−3) of in situ boron-doped LPCVD-polysilicon thin films before and after thermal-oxidation treatments are presented. Measurements of the precedent characterisation methods (SIMS) are performed on submicron layers (300 nm) deposited at the extreme temperatures Td = 520 °C and Td = 605 °C. The thermal-oxidation experiments are carried out under dry oxygen (O2) at three oxidation temperatures Tox = 840 °C, 945 °C and 1050 °C for several durations. After these thermal-oxidation processes, remarkable changes in the behavior of doping profile are observed. This behavior seems to be typically characteristic of the in situ heavily boron-doped films. In addition to the presence of some saturation-thermal-dependence phenomenon, we find that these results well correlate and support the presence of another phenomenon called “Differential of the Oxidation Rate (DOR)” which is evidenced as typical of the in situ doped films.

The noise and mode-locking phenomena of a hybrid soliton pulse source (HSPS) utilizing different fiber Bragg gratings (FBG) with or without linear chirp are described. The HSPS is modeled by a time-domain solution of the coupled-mode equations including spontaneous emission noise, and relative intensity noise (RIN) is calculated using numerical solutions of these equations. It is found that transform-limited pulses over a wide tuning range around the fundamental mode-locking frequency are generated from mode-locked HSPS with linearly chirped uniform and Gaussian apodized FBGs. Mode-locked pulses that are not transform-limited are generated over a wide tuning range from HSPS with Gaussian apodized and uniform FBGs. These gratings can give transform-limited pulses only over a limited tuning range around the fundamental mode-locking frequency. It is also found that RIN reduction is possible for the mode-locked HSPS by selecting a suitable apodization function such as Gaussian and linear chirp rate.

The influence of environmental conditions “film thickness and measurements in both under vacuum and in air” on dark electrical resistivity of (E) [α(2,5Dimethyl furyl) Ethylidene] (Dicyclopropyl Methylene) 2,5 furadione thin films were investigated. It was found that electrical resistivity decreases exponentially with increasing film thickness and it is higher in those films measured under vacuum than those measured in air. The parameters and mechanisms of conduction in P-DCPF/n-Si heterojunction diode has been evaluated. For temperatures that is less than 351 K, the conduction mechanism is Schottky emission with thermal activation energy of 0.32 eV. In the temperature range “352−400 K”, the predominant conduction mechanism is space charge limited current with thermal activation energy of 0.95 ± 0.02 eV. The conduction mechanism in reverse bias direction is generation-recombination with activation energy of 0.57 ± 0.02 eV. The photovoltaic properties of P-DCPF/n-Si heterojunction diode were evaluated. The obtained experimental efficiency of constructed solar cell is 1.27%.

This paper investigates the self-heating effect in SiGe heterojunction bipolar transistors. A physical study leads to a nonlinear physical model describing static and dynamic self-heating mechanism. The implementation of this model using an electrical equivalent circuit is presented. Our approach is validated using measurements on devices from different technologies. System configuration, measurement, and calibration issues are presented.

This work describes the application of the Lattice Fringe Spacing Measurement (LFSM) method to the study of complex multiquantum well heterostructures containing both low-misfit and strain compensated short period superlattices in barriers and wells, respectively. 90°-wedge cross-sectional samples have been used. The adequate choice of both experimental conditions and digitized sampling allows the whole heterostructure to be visualized and studied in a single High Resolution Transmission Electron Microscopy (HRTEM) image. Sample preparation and image processing technique are simple and inexpensive, resulting a fast procedure particularly suited for the analysis of large areas. By this way, in a single HRTEM image we have measured, in the growth direction, the lattice spacings at either side of the multiple grown interfaces as well as the period variations of both types of superlattices; in addition, we have measure on the same image the lattice strain in a direction perpendicular to the growth direction by using the LFSM and the Cumulative Sum methods. We have observed local lateral variations within the wells, with regions tensile or compressively strained, while a vestige of the grown SL remains, indicating the occurrence of a strain induced lateral composition modulation process spontaneously produced during the growth of strain compensated short-period superlattices. This is further confirmed in cross-section prepared by the tripod mechanical polisher method.

Density, molar volume and ionic field strength changes induced by addition of ThO2 to $\rm 2P_{2}O_{5}\cdot Na_{2}O$ glass matrix are correlated in order to understand the structural role of thorium oxide in the investigated glasses and to evidence the structural evolution of the samples as a function of composition. Gamma activity measurements are used to check thorium incorporation in the soda-phosphate matrix.

Neodymium nickelate thin films have been prepared on NdGaO3 substrates by RF magnetron sputtering and post-annealing treatment under oxygen pressure. Transport properties are found to depend strongly on film thickness. Thick films show transport properties close to bulk ceramics, while very thin films exhibit a large transition from metal to insulator which occurs over a wide temperature range with high resistivity. Structure and surface morphology of the films have been investigated by Transmission Electron Microscopy (TEM) and Atomic Force Microscopy (AFM). Thin films (≈17 nm) grow heteroepitaxially, while thicker films (≈73 nm) show a granular structure. The thinnest sample suggests a symmetry change induced by the epitaxial strain of the substrate. This paper discusses the relationship between microstructure and transport properties.

Calculated values of viscosity, thermal conductivity, electrical conductivity, density and specific enthalpy of plasma formed in five different insulators vapours (PE, POM, PMMA, PC and PA66) are presented. The calculations, which assume local thermodynamic equilibrium, are performed for three pressures (1 atm, 10 atm, 100 atm) in the temperature range from 5000 to 30000 K. The results for PE, PMMA and PA66 are compared with those of other authors at atmospheric pressure. Significant discrepancies are found; these are attributed both to differences in the collision integrals and to the formulation used in calculating the transport coefficients. We give all the data for the potential interaction and the formulation necessary to obtain reliable values of transport coefficients.

Thin films of PbZr$_{(1-x)}$TixO3 have been elaborated using the sol-gel process. We have characterised the thermal behaviour of the sol and of the film of PZT. The different orientations were observed according to the temperature of pyrolysis: [111] at 500 °C, [100] at 450 °C. Finally, an advanced method of electrical characterisation of ferroelectrics is used by separating the reversible and irreversible contributions of polarisation. An experimental Preisach density is then measured and modeled and allows to extract ferroelectric properties. These parameters are independent from electric field strength applied through the sample, leading to a powerful tool to characterise the electrical behaviour.

The ablation rate of sintered polytetrafluoroethylene (PTFE) targets has been investigated as a function of wavelength within the range $193 \le \lambda \le 1064$ nm and pulse durations $5 \le \tau _{l} \le 25$ ns by means of various different lasers. In this parameter range, the apparent optical properties of targets and the depth of energy deposition are determined mainly by the scattering of the laser light. Therefore, measurements of the scattered light were performed for samples of various thicknesses by means of a modified UV-VIS spectrometer. For selected wavelengths, the angular distribution of the reflected and transmitted light intensity was determined. From these measurements, the coefficients for linear absorption, linear scattering and the scattering anisotropy were calculated using the inverse adding doubling algorithm. The results were tested by Monte Carlo simulation. With these coefficients the apparent optical penetration depths were estimated. These are about one order of magnitude larger than the ablation depths per pulse, which were determined from the weight loss of the targets. Laser deposition

A new fast method is used to analyze positron annihilation lifetime spectra. The regularization procedure to solve the inverse problem of finding parameters of useful signals present in the data is formulated. A new approach to determine the number of components in a spectrum is proposed. Results on simulated spectra demonstrate the high resolution capability of the method.

This paper deals with duality based approaches of field computations. It presents two methods that allow to obtain upper bounds for the error on the forces or torques. The first one is based on a double evaluation of the global coenergy for two values of the position. The second one resembles the popular Maxwell's tensor method and requires the field computation only once, but respecting an additional rule. For both methods, the force or torque are considered in respect of their average value on an interval of displacement, taken as configuration parameter.

Low concentration of toxic radioactive metals in environmental samples often limits the interpretation of results of infrared studies investigating the interaction processes between the metal ions and environmental compartments. For the first time, we could show that photothermal infrared spectroscopy performed with a pulsed free electron laser can provide reliable infrared spectra throughout a distinct spectral range of interest. In this model investigation, we provide vibrational absorption spectra of a rare earth metal salt dissolved in a KBr matrix and a natural calcite sample obtained by photothermal beam deflection (PTBD) technique and FT-IR spectroscopy, respectively. General agreement was found between all spectra of the different recording techniques. Spectral deviations were observed with samples containing low concentration of the rare earth metal salt indicating a lower detection limit of the photothermal method as compared to conventional FT-IR spectroscopy.

Acoustic pulse propagations in typical environments of the Gulf of Mexico and Yellow Sea are modeled by a new normal mode code, SWAMP, and compared to the experimental data. The presence of the seasonal surface duct in the ocean is confirmed to be responsible for the generation of a unique set of modes forming the so-called “Precursor Phenomenon” first discovered by DeFerrari and Monjo. It is shown that the conventional theory of group velocity fails to predict precursor's arrival time. Two different approaches, the mean rate of energy transport and Airy-wave analysis, are proposed for the description of the actual physical process of energy transport by precursors. The influence of the range-dependent bathymetry on a precursor structure is addressed. The presence of precursors appears to be sensitive to range dependence and may be diminished due to rapidly changing bathymetry. Based on numerical results, inversion procedures of extracting different environmental and source parameters from a received pulse structure are discussed.

We propose a new method of molecular microwave spectroscopy together with analysis ofresonance line shapes, based on the fast passage effect. The fast passage effect isthe excitation of coherent spontaneous radiation of tested molecules using a fastfrequency sweep over the absorption line. We show that the line shape can bereconstructed from the received detector signal with the use of Hilbert and Fouriertransformations. We find that sensitivity of a fast passage spectrometer is higherthan that of an ordinary pulsed Fourier-transform spectrometer. The proposed method isa useful tool for fast analysis of gas mixtures.

The spatial transition behaviour of the electron gas on its way from a uniform active plasma through an adjacent region of field decay and reversal into a field-free remote plasma is studied in neon on a nonlocal kinetic basis by solving the appropriate electron Boltzmann equation and by performing complementary Monte Carlo simulations. The main objective of the analysis concerns the complex features of the electron gas in its transition process from a field-driven active plasma, through a range of partial electron trapping in a potential energy valley to a diffusion-driven remote plasma. In this context especially the influence of the electron trapping and of the extent and depth of the potential valley is elaborated. In addition to the macroscopic characterization by means of the important transport and dissipation properties of the electrons their energy space resolved behaviour is derived and interpreted. A distinct decoupling between the spatial evolution of the isotropic and anisotropic part of the velocity distribution function and complex structures in the anisotropic part have been found. These findings could be clearly confirmed by the almost perfect coincidence with corresponding results obtained by the MC simulations. Glow; corona

This article deals with the analytical modelling of piezoelectric cylindrical micromotors [Morita et al., Jpn J. Appl. Phys. 35, 3251 (1996) and IEEE Trans. Ultrason. Ferroelectr. and Frequency Control 45, 1178 (1998)] and supplements the kinematics analysis of Pin Lu et al. [Sens. and Actuators A 87, 194 (2001)]. The modelling, based on an equivalent electric circuit, is established using geometrical and electromechanical parameters for the different parts of the motor. It gives electromechanical characteristics and other useful values for motor design.

Angiogenesis ensures the success of cancer growth. This enlargement of the vascular system feeding a tumor is induced by tumor angiogenic factors (TAFs), which are molecular messengers emitted by starving cancer cells. We apply a recently developed angiogenesis model to study the influence of variations in the TAF generation rate on vascular growth and to analyze the effects of changing the threshold for endothelial cell transformation, which is a crucial parameter in the description of this process.