We have used scanning tunneling microscopy to examine N-terminated Cu(111) surfaces. For substaturation N coverages, elongated rectangular islands are formed, the internal structures of which are in good agreement with a model proposed in a previous LEED study. These islands sufficiently perturb the surface so as to reflect surface state electrons in the adjacent clean surface regions. This results in the observation of electron standing wave patterns. We have simultaneously observed both the electron wave patterns and atomic resolution. We have also shown that under conditions of high electric fields, the N atoms at the surface can be forced down into the second layer with Cu atoms liberated from the first layer to form single layer high islands.

In this paper we extend the recently developed models that predict the magnetic field produced by thermoelectric currents around spherical and cylindrical inclusions to the case of elliptical cross-section cylindrical and spheroidal inclusions. The extra geometrical complications are handled by utilizing already available solutions of similar problems in hydrodynamics and electricity. It is shown that the results reduce to those of the previous models when the aspect ratios of the inclusions equal unities.

The optical properties (refractive index and optical energy gap) were studied as a function of film thickness, substrate temperature and heat-treatment temperature for structurally, compositionally and morphologically well characterized CdI2 films grown by thermal evaporation. The variation of residual stress in the film (determined by X-ray diffraction), grain size (D), refractive index (n) and optical energy gap (Eg) was observed to be different in the above three cases. Combining the results of all three experiments, the grain size dependence of n and Eg was derived. Variation of n with grain size may be attributed to the changing packing density of crystallites with grain size and its distribution consistent with SEM results. Eg was found to decrease with D non-linearly and the data fits well with the equation of the type either $E_{\rm g}(D)=3.61-0.023D-0.0034D^2$ or $E_{\rm g}(D)=3.59-\frac{0.075 D^2}{(2+D)}\cdot$ The variation of Eg with D could be attributed as due to the defect densities in the film.

We have studied the electrical conductivity of Cs vapor cells in the temperature range 190−270 °C with Cs atom density up to 3 × 1014 cm−3. Depending on these parameters controlled independently, two predominant mechanisms are shown to determine the electrical properties of the cells: wall surface conductivity and space conductivity. The latter is caused by thermionic emission of electrons from the “cesiated” surface at submonolayer coverage. This process has been studied for the case of metal (Ti) and dielectric (Al2O3) surfaces. The values of the electron emission work function are found to be 1.38–1.42 V for Ti, 1.4–1.45 V for alumina and 1.39 V for sapphire. From independent photoemission studies, we also obtain the value of 1.35–1.40 V for the work function of sapphire. Our measurement technique not requiring internal electrodes can easily be implemented for studies of charge emission and ionization, in different types of dielectric cells containing a low density gas medium.

Binary tellurite glass systems of the forms TeO2(100−x)-xAn Om whereAn Om = La2O3 or V2O5 and x = 5 to 20 for La2O3 and 10 to50 for V2O5 were prepared. UV-spectra of these glasses were recorded in the range of200–700 nm at room temperature. The optical energy gaps E optical and $E_{\rmtail}$ have been calculated from the optical absorption edge. UV cut-off and IR cut-off havebeen measured. Calculations of the oxide ion average polarizability ( $\alpha_0^{2-}$ ) andoptical basicity (Λ) have been done.

Plasma sputter deposition experiments and simple molecular dynamics calculations are performed for highlighting the effects of plasma ions and kinetic energy of palladium atoms on the morphology of thin films. A transition between cluster and continuous film growth is observed. It is attributed to the kinetic energy of the depositing sputtered palladium atoms and to high binding energy trapping sites resulting from the effects of ions incident on the surface during deposition. These high binding energy trapping sites act as additional nucleation centres that are allowed to be visited by the diffusing Pd atoms.

Absorption of electromagnetic energy in human tissues is an important issue with respect to the safety of low-level exposure. Simulation is a way to a better understanding of electromagnetic dosimetry. This letter presents a comparison between results obtained from a numerical simulation and experimental data of absorbed energy by a muscle. Simulation was done using a bidimensional double-scale homogenization scheme leading to the effective permittivity tensor. Experimental measurements were performed at 10 GHz on bovine muscle, 30 hours after slaughter, thanks to the open-ended rectangular waveguide method. Results show a good agreement between measurements and simulated data.

We have performed Monte-Carlo simulations of slow electrons impinging on semi-infinite aluminum and copper in the energy range 0.5–4 keV. We present results for the backscattering coefficients, mean penetration depths and stopping profiles. Our results for the backscattering coefficients agree well with the experimental data within the limits of the statistical accuracy. The slight discrepancy between simulated and experimental results regarding the mean penetration depth is discussed.

New composite materials based on aluminosilicate materials were developed to be used in orthopaedic or maxillo-facial surgery. They are called geopolymers or polysialate-siloxo (PSS) and were studied alone or mixed with hydroxyapatite (HAP). The properties of these materials were investigated for potential use in biological or surgery applications. In this work, the chemistry involved in materials preparation was described. Samples were characterized by some physico-chemical methods like X-ray diffraction (XRD), infrared spectrometry (IR) and electron dispersion X-ray spectrometry (EDX). Results indicate that the mixing hydroxyapatite-geopolymer (PSS) leads to a neutral porous composite material with interesting physico-chemical properties. A preliminary evaluation of its cytotoxicity reveals an harmlessness towards fibroblasts. These properties allow to envisage this association as a potential biomaterial.

The (Ba0.67Sr0.33)TiO3 thin film for dielectric bolometer mode of uncooled infrared focal plane arrays prepared on Pt/Ti/SiO2/Si by radio-frequency magnetron sputtering has been investigated focusing on the dielectric properties. X-ray diffractometer shows the BST films to be well perovskite structure. These films exhibit good surface morphology. The dielectric properties of the BST thin films have been measured as a function of temperature using a HP4284A LCR meter. According to the dielectric constant-temperature curve, the Curie temperature of the BST thin film is about 30 °C, around room temperature. The maximum change in the dielectric constant is as large as 78/k, and more than 21% relative change in the dielectric constant has been obtained.

Simple formula for microscopical estimation of the Debye temperature for polyatomic crystals is reported. It is based on the calculation of the force constants for arbitrary pair of interacting atoms by means of the phenomenological spectroscopy data for oscillation frequencies of homonuclear molecules. For that purporse a special combinative rule is suggested. The table of necessary parameters for calculation of Debye temperatures of arbitrary crystals and solid solutions is included.

A theoretical overview is given about the influence of the presence of the X-valley in highly doped n-GaAs on hot free-electron absorption and optical nonlinearities at 10.6 μm wavelength. The implications of the extension of the quantum-mechanical model from two to three valleys are discussed. For electron temperatures above 600 K the X-valley presence starts to be observed. We reveal that it is difficult to trace the individual contributions of different X-electron related inter- and intravalley absorption and relaxation phenomena and therefore we suggest to introduce an effective X-valley related deformation potential which is a weighted combination of all the X-valley contributions. We discuss how nonlinear optical experiments can be conducted to determine the LL-intervalley and this effective X-valley deformation potential.

A large variety of initiation results in a ram accelerator have shown that a series of interactive parameters play a key role, such as the design of the facility, tube diameter, shape of both the projectile and sabot and the choice of the reactive propellant mixture. Two different ram accelerators were used at ISL for this study, namely a 30-mm and a 90-mm-caliber. In addition to the diameter effect, it was observed that the dimension of the sabot must be adapted not only to the caliber of the tube but also to both the launching device and vent section that are located before the ram accelerator tube. For instance, a sensitive mixture yielded a superdetonative mode in the larger tube diameter facility at ISL. Comparative experiments were conducted in these two caliber ram accelerators at ISL. Important transient effects were observed as the projectile enters the tube which could explain the discrepancies between the data derived from similar devices. The aim of the present paper is to provide a series of data that show the effect of the tube diameter on the initiation process of the propellant mixtures that are currently used in this facility. The design of the sabot is also discussed.

A one-dimensional radiation magneto-hydrodynamics code coupled to an atomic kinetics code was developed, whose simulation results were compared with the experimental observations. Based on the simulation results, the physical processes and physical scheme of Z-pinch implosions were studied. During the implosion phase, the plasmas are heated and ionized, and before the stagnation, the greatly ionized plasmas of high temperature and high density are created. Then the continuously rising density leads to the recombination of plasmas and the emission of an intense X-ray pulse. Our simulation shows that there are two necessary conditions for producing high yield of K-shell energy. Firstly, highly ionized plasmas must be prepared before the beginning of recombination. Secondly, the density of the plasmas which are in recombination phase should be high enough to make the plasmas recombine with a large rate so that more internal energy can be drawn before stagnation. As another result of our study, the atomic processes play a role in cooling free electrons during the recombination phase.

A hyper-frequency method enabling to investigate into the bubble size distribution of a bubble cloud in which bubble radii are lower than the equilibrium one is displayed. It is based on analysing the void rate dissipation after the acoustic irradiation is switched off in terms of bubble dissolution. The experimental evaluation of this method has been performed in air saturated water with cavitation bubble cloud generated in a 308 kHz stationary acoustic field. The size distributions achieve range from 19 μm to 59 μm and allow to follow the influences of both the acoustic pressure and the irradiation duration on them. By taking into account the bubble coalescences occurring during the bubble rise after the end of the acoustic irradiation, the raw distributions have been qualitatively nuanced thanks to the exploitation of a probabilistic model of free bubble coalescence.

The excess leakage current due to the ion implantationisolation process used in the fabrication of double mesa Self PassivatedGaAlAs/GaInP/GaAs Heterojunction Bipolar Transistors (SP-HBT) has been investigated.This ion implantation process, used to limit the active emitter length results in a drasticreduction of the current gain. The ideality factor of the recombination current associatedwith the ion implantation has been found to be 1.8, close to the conventional value of 2.

The tunable operation of an all solid-state diode pumped Raman laser on a Yb:KYW crystal is demonstrated. The possibility of a simultaneous tunable operation for laser generation in the 1029–1032 nm range and Stokes generation in the 1136–1139 nm range is shown. A slope efficiency of 12% and a maximum average power of 14.5 mW were achieved for the Stokes output.

The use of spectrophotometers for the measurement of cell concentration in yeast suspension is critically discussed. Corrections are derived which take into account cell size, shape, cell aggregation (flocculation) and non linear effects related to sample thickness.

Pulsed photoacoustic spectroscopy (PPAS) provides a convenient means for in vivo and in situ monitoring of human skin properties and surface concentrations of locally applied substances, such as drugs and cosmetics. In this article, we applied the one-dimensional theoretical model of Mandelis and Royce (J. Appl. Phys. 50, 6 (1979)) to simulate the photoacoustic response of human skin and diffusion phenomena through it, for various optical absorption coefficients and sample thicknesses. This approach is analyzed through the temperature and pressure variations in the photoacoustic cell.

Organic filed-effect transistor (OFETs) based on polycrystalline “octithiophene” has been realized. The current-voltage characteristics at low drain voltage has been used to derive the mobility of organic field effects transistors (OFETs). It appears that the data must be corrected for the substantial source and drain contact resistance. The carrier mobility is found to increase quasi linearly with gate voltage at room temperature. The temperature dependent measurements show that the mobility is thermally activated and becomes practically temperature independent at low temperatures. A model based on trapping mechanism, in which it is assumed that charge transport is limited by grain boundaries, has been used to describe the carrier mobility in polycrystalline “octithiophene” thin film transistors measured at temperatures ranging from 10 K to 300 K.