We have supposed a new approach for the investigations of the effect of roughness on the propagation of the elastic surface waves. The presence of the rough layer is accounted by the modification of the boundary conditions. In the framework of this approach we have investigated the propagation of Rayleigh waves on an isotropic substrate having rough surface. It is shown that the roughness leads to the linear dispersion of the phase velocity of the surface waves, which are non dispersive on the ideal surfaces. Also we have investigated the influence of a rough surface of films, deposited on the substrate. The roughness of the film surface produces contributions to the phase velocities of Love and Rayleigh modes. In all cases the contributions are proportional to the effective thickness of the rough layer. It is shown that the effect of the rough layer is equivalent to the effect of a thin film, having loading characteristic. The approach can be used for investigations of the effect of roughness on the propagation of surface waves on the rough surface of the anisotropic crystals.

We have studied the microstructure and morphology evolution in PbSe films chemically deposited on GaAs(100) substrates. The films consisted of a single phase of nanocrystalline rocksalt PbSe. The deposition temperature was found to be an important parameter which strongly influences the film morphology. A gradual transition to strong (111) texture was obtained with increasing deposition temperature, accompanied by a significant increase in crystallite size. Transmission electron microscopy (TEM) cross-sections showed two distinct regions. A layer of small, rounded crystals near the GaAs/PbSe interface above which a second region composed of columnar, $\langle$111$\rangle$ oriented crystallites was observed. High resolution TEM and Fourier analysis showed that the first layer of crystallites are in epitaxial registry with the GaAs substrate, in spite of the large (8%) lattice mismatch and the presence of a thin, amorphous interfacial layer.

The modified expression for Debye-Waller factor is derived for the scattering of X-rays from rough surfaces and interfaces. For the large values of scattering vector, the non-Gaussian behaviour of this factor is predicted. This effect can be essential for interpretation of X-ray reflectivity from very rough surfaces and high-order X-ray diffraction data. The experimental X-ray reflectivity measurements are interpreted using the derived expression.

A possible application of nanometer-sized junction arrays is to Coulomb blockade thermometry (CBT), although only highly disordered arrays can be fabricated at present. In this paper, the characteristics of CBT device with disordered arrays will be studied. Similar to what is observed for uniform arrays, there is a dip at zero bias voltage in the differential conductance of disordered arrays. However, the half-width $V_{1/2}$ of the dip for one-dimensional disordered arrays is largely dispersed. This study suggests that better devices can be developed by connecting a number of one-dimensional arrays in parallel to form an array group. The dispersion of half-width is quite small with values of $V_{1/2}$ close to a constant. Further, the effects of electromagnetic environment and low temperature on the half-width are investigated. Results are agreed with those observed experimentally, that for the effect of the environment is negligible for large arrays. The half-width of a disordered array may be bigger or smaller than the ideal value, depending on the extend of disorder.

Calorimetric studies have been performed on the Se$_{80-x}$ Te20 Pbx ($0 \leq x\leq 1.4$) samples at different heating rates (5−20 °C/min). The glass transition temperature Tg, the peak crystallization temperature Tp, and the melting temperature Tm are found to increase with increase in heating rate. The apparent activation energies for glass transition Et and for crystallization Ec have been calculated from the heating rate dependence of Tg and Tp respectively. The effect of Pb addition to the Se-Te matrix on the mechanism of crystal growth has been investigated. The glass transition temperature Tg and the peak crystallization temperature Tp initially decrease with small addition of Pb (x = 0.6) but increases with further addition of Pb (x > 0.6). The thermal stability and glass-forming tendency have also been studied.

This paper presents a study of the damage production in yttria-stabilized cubic zirconia single crystals irradiated with medium-energy (from 30 to 450 keV) heavy ions (from He to Cs). The disorder created in the two sublattices (Zr4+ and O2−) of the crystals and the lattice sites of heavy ions were determined as a function of the irradiation fluence by in situ Rutherford backscattering and channeling experiments using a 3 MeV 4He ion beam. Damage is created at a depth close to the ion projected range at low fluences and growths towards greater depths with increasing fluences once the saturation has been reached. The kinetics of the damage accumulation process reveals three stages, which (excepted for He) essentially depend on the number of displacements per atom (dpa) induced by irradiating ions (ballistic contribution). Channeling results show that the lattice location of the heaviest atoms (Xe, Cs and I) varies with the nature of implanted species (chemical contribution). The experimental data can be represented in a diagram involving both the number of dpa and the implanted ion concentration, which could be used to predict the damage evolution in other ion-irradiated nuclear ceramics.

In previous work, we have presented a computation method based on the determination of the Green functions of the electromagnetic field with the help of the spectral moments method (SMM). In this method, the Green functions are calculated in the form of continued fractions, and one determines the coefficients of their development. Two approaches have been presented: one, we call global approach, where all space is discretized in a box, the other, we call the local approach, where only the diffracting item is considered. In this work we present the results obtained for the one, two and three-dimensional cases by the local approach. We first develop the necessary tools for the computing. We establish the analytical form of the Green functions of the continuous vacuum and of the discretized vacuum, the dispersion curves and the selection rules which appear. We show that the real part of the diagonal Green functions is directly linked to the vibrational density of states and therefore perfectly determined whatever dimension the space is. Longitudinal, non physical modes are found to play a subsequent role. As regards scattering, we principally report a series of tests on some canonical systems, such as cylinders or spheres, showing that the backscattering cross- section and the impulsional response obtained with SMM are in very good agreement with the analytical results. Bi-static scattering cross section is also studied.

As most part of the industrial effluents contain carbon dioxide and water vapour, it is interesting to study from an electric point of view ‘basic’ gas mixtures including air and various amounts of these gases, in order to precise how the corona discharge inception takes place in such mixtures. In a DC point-to-plane reactor, distinct parameters are varied, such as discharge current, partial pressure of CO2, and relative humidity. Gap voltage and streamer frequency are experimentally measured as functions of the discharge current. Current waveforms are recorded in various gas mixtures and electrical conditions. DC and impulsional current components, as well as streamer frequency are also plotted as functions of the CO2 partial pressure for dry and water saturated mixtures. For dry or wet mixtures, 5% CO2 in volume appears to be the proportion allowing the establishment of a stable corona discharge with the lowest energy cost.

The transition from low pressure corona (dark discharge) to glow discharge is studied for nitrogen in the 1–10 mbar pressure range in DC positive point-to-plane geometry for various cathode materials. A systematic study of the spatial distribution of the discharge's light intensity, correlated with the current impulses recorded at the cathode, is performed by focusing on the slit of a photomultiplier the light emitted from small regions along the gap axis. For pressures higher than 2 mbar, the luminous activity of the discharge, amplified by a photomultiplier, is characterized by complex impulse waveforms. A study of these waveforms shows that a weak light peak initiated at the anode, propagates towards the cathode with increasing velocity and amplitude. Travelling slower than a streamer, this impulse may be attributed to a weak ionizing front accelerating in the middle of the gap. A second peak is superimposed in the anode-sided half interval, the interpretation of which, supported also by numerical simulations, could reveal the fast propagation of a new front. The influence of cathode material on this second peak shows that it is in fact linked to the secondary emission of the cathodic region. From the analysis of these results, the transition appears to be a complex physical process beginning by a weak ionizing wave starting at the anode and propagating towards the cathode. The arrival of this wave in the cathode region enhances the local field and contributes to the amplification of the cathodic secondary processes. Arriving in the anode region, the secondary electrons initiate a new ionizing wave, stronger than the first one, which crosses the gap very rapidly and establishes the glow discharge.

This paper presents new developments of the BNM-INM heterodyne compact refractometer. Air refractive index measurements have been made at 633 nm with a relative uncertainty of 10−8 and the realization of a new type of wavelength stabilized laser source has been demonstrated at 633 nm. We now have adapted this source to a commercial interferometric system working at 633 nm. Length variation measurements in air have been made. Results show that the wavelength of our source is insensitive to slow variations of the refractive index of air at a level of 10−8, demonstrating the possibility to make distance measurements in air without the need to make any index correction.