Table of contents

We present scanning tunnelling microscopy results of thin dysprosium silicide films grown on Si(001) 21. At submonolayer coverages, up to 2000 Å long wires are formed in the (110) direction of the Si(001) surface. Depending on Dy exposure and annealing conditions, both wire assemblies and free-standing wires can be grown. At higher coverages, three-dimensional clusters with rectangular shapes are formed.

Liquid gas was used to produce diamond-like carbon (DLC) films on Cu, Al and steel substrates by a dc plasma technique. The absorption in IR reflectance indicates that the grown films are DLC. By deconvolution of room temperature UV visible spectra of the films grown at 50 mTorr and 200 , in addition to the spectra lines reported for cathodoluminescence, photoluminescence, positron-life-time spectroscopy and electron-spin resonance, some new spectral lines were obtained. We have also seen an exciton absorption line at room temperature.

The high room-temperature carrier mobilities which have recently been observed for both electrons and holes in Si/SiGe heterostructures and the possibility of further improvements offer the prospect of silicon-based field effect transistors (FETs) with performances matching those of bipolar transistors and III-V modulation-doped FETs. In this article the electrical properties of this semiconductor system and the associated materials challenges are discussed, and some of the more important device applications are reviewed.

The contact law and consequent pressure distribution for contact between elastic spheres with a meniscus of cohesive fluid are found. The results reveal quite a different relationship both from conventional dry contact and from contacts whereby solid-solid adhesive forces apply. The results are of direct applicability to the study of agglomerates. A direct indication of the pull-off force between adjacent spheres is given, but for a numerical evaluation of this force the Kelvin curvature and contact angle are needed.

The propagation characteristics of microwave frequency surface waves along atmospheric pressure plasma columns sustained in capillary tubes by these same waves are studied analytically and numerically. In contrast to what has been done to date in such a pressure range, our analysis includes the modelling of the discharge processes in order to account for their interdependence with the wave's propagation. To describe these processes and to determine the plasma parameters, we turn to a two-temperature model for non-equilibrium plasmas. The analysis of the wave dispersion is performed using a cold plasma, linear dielectric description; it assumes the local uniformity approximation, which is scrutinized. Also, we assume that the phase and attenuation coefficients of the wave, under given discharge conditions, depend only on the amount of power dissipated in the plasma per unit length. The obtained results are compared with known experimental data.

Single crystals of were grown from a melt and characterized by various experimental techniques, such as x-ray diffraction, x-ray photoelectron spectroscopy (XPS), and electrical and photoluminescence (PL) measurements. Our investigation evaluated important parameters of this challenging material. In particular, we studied here for the first time the electronic structure, the excitonic effects and the impurity bound states of , by means of XPS and by analysing dependences on the temperature and the excitation intensity of the PL spectra.

During laser materials processing, the melt pool can form a convex or concave surface depending on the processing conditions and surface tension of the liquid metal. The curved surface can act as a lens to refract the laser rays. Temperature distributions below the substrate's surface are calculated for various values of the attenuation coefficient and radii of curvature of the free surface of the melt pool. For convex spherical curvature and a large penetration depth of the laser beam, the subsurface temperatures are found to be extremely high, exceeding the surface temperature severalfold. This is because of self-focusing, that is further focusing of the laser beam, that causes high subsurface laser irradiance.

The electrokinetic characteristics (the electron energy distribution function, the strength of the longitudinal electric field and the concentration and average energy of electrons) are measured and calculated in a -discharge plasma under a high pressure of argon (up to 30 Torr) and in narrow tubes (the tube radius is less than 1.0 cm). A simple method of treating the second derivative of the probe current with respect to the probe potential is proposed for a straightforward way to obtain the electron energy distribution function under a high pressure of a gas. It is shown that the main assumptions on which modelling of the plasma of mercury luminescent lamps is based are also valid for the plasma in question. This leads to the existence of special similarity laws and gives a new possibility for diagnostics based on the similarity properties of the plasma. The approach proposed in the work can be easily extended to the mixtures of mercury vapour and other rare gases.

The analysis of the Balmer H and H emission line shapes in a 2 MHz radiofrequency Ar- glow discharge, used in a plasma-assisted CVD reactor, reveals anomalous Doppler profiles which indicate that atomic hydrogen has two kinds of average kinetic energies. These energies vary with the distance z to the grounded substrate and are -0.4 eV for the slow (low-energy) hydrogen and 6-24 eV for the other. Moreover, the Doppler broadenings observed for Ar, and lines lead always to energy values lower than 0.15 eV. From the optical emission signals and a relevant discussion, it is established that would be the origin of the fast hydrogen. Its energy would be limited by charge transfer between and whereas the slow molecular hydrogen would give rise to slow hydrogen by a dissociative excitation mechanism.

A new method for measuring the vacuum leakage of a pressure sensor proposed by the present authors has been improved so that it can be applied for industrial use. The principle of this method is based on the discharge characteristic called Pashen's law. The main improved points are reduction of fluctuation of the discharge potential and extension of the measurable pressure range. As a result, a leakage rate of Pa can be detected within a day. This sensitivity is comparable to that of the radio-isotope method now in practical use or even higher than that. The measurable pressure range is enlarged from 70-150 Pa to 70 Pa to a few hundreds pascals by employing He gas to detect the leakage.

The current thrust on the use of environmentally friendly technologies for cooling applications, inter alia, envisages the adoption of adsorption systems. Adsorption chillers are known to be `inefficient' due to their low coefficient of performance. Although the basic physics of heat and mass transfer in various components of the system is well understood, there is a lacuna in the quantification of irreversibilities. In this paper, a silica gel-water, two-bed, non-regenerative chiller is analysed. It is shown that the largest cycle-averaged rate of entropy generation is in the beds and that the least is in the condenser. The entropy generation rates in the beds are further studied, showing that the maximum contribution is made during the switching phase. In general, manufacturers' effort to maximize cooling capacity is shown to correspond to maximum entropy generation in the evaporator.

Ultrasonic standing waves, excited in an (111) crystal through magnetoelastic coupling, are visualized using synchrotron radiation diffraction imaging (`topography'). This observation relies on the possibility at the ESRF of recording images with long sample-to-film propagation distances (up to 1.5 m) without substantial loss of resolution. The crystal acts as an x-ray focusing lens periodically in time, an effect that strongly depends both on the amplitude of the magnetic field excitation and on the propagation distance. The standing-wave-related contrast is hardly visible close to the sample, very sharp for a focusing distance (typically ) whereas beyond this position the intensity maxima broaden due to the defocusing effect. We propose a model which accounts for the presented results, allows the understanding of the details of the resonance patterns and gives access to the main characteristics of the vibration: amplitude, shape, polarization, wavelength and sound velocity. This effect could be used to simultaneously monochromatize and focus the x-ray beam simultaneously.

In this paper we report the study of plasmas generated when the laser beam hits a target surface in the middle of a hole through the target, the diameter of the hole being slightly smaller than the laser beam's waist. The hole's axis coincides with the laser beam's axis. In such a case two plasma clouds are observed: one expands from the front hole opening towards the laser, the other from the back side of the target in the opposite direction. The experiments indicate that the plasma in front of the target is similar in appearance to the plasma generated by ablation of a planar surface. On the other hand, the plasma behind the target is significantly less dense and is also much colder than the corresponding plasma in front of the target.

Ruthenium bipyridyl complexes have been used as efficient sensitizers for photoelectrochemical cells based on nano-porous films of . It is found that cis-dithiocyanate-bis(2,2-bipyridyl-4,4-dicarboxylate) ruthenium (II) can be used as the sensitizer in a solid-state photovoltaic cell in which a monolayer of the sensitizer is sandwiched between nano-porous n- and p-CuI. The data on performance of the cell and the problems encountered in construction of dye-sensitized solid-state photovoltaic cells are described.

The next to last paragraph of this paper should read as follows.

It should be pointed out that equation (1) can be used to obtain the value of the transverse coherence function [1, 2]

where and r is the distance between two points in the plane, perpendicular to the incident wave. Note that there is the similar formula for the optical transfer function [2]

where , p is the dimensionless angular frequency. Equations (1), (2), (11), (24) and (25) can be derived from the same general solution [2], obtained in the framework of the SAA. They were applied to optical particle sizing problems under multiple light scattering conditions in [7, 8, 15-27]. Therefore, different optical particle sizing techniques have the same theoretical background.