Table of contents

This review is devoted to the angular selectivity that can be obtained in thin films prepared under conditions such that they contain inclined absorbing regions of sizes much smaller than the wavelength of visible light. The films are of considerable interest as window coatings for energy-conscious architecture and, potentially, in the automotive sector. The theoretical basis for modelling the optical properties is presented, comprising rigorous bounds on the dielectric function, effective medium theories pertinent to different microgeometries and equations for treating the optics of anisotropic thin films. Experimental data are reported for films made by oblique-angle evaporation of Cr and for reactive and non-reactive oblique-angle sputtering of Cr, Al, Ti and W. The highest angular selectivity was obtained with evaporated Cr, whereas the highest luminous transmittance, combined with some angular selectivity, was found with reactively sputtered Al. Films made from Ti showed angular selectivity mainly in the infrared, whereas films made from W could display angular selective electrochromism. Samples of several types were subjected to elaborate theoretical analysis using effective-medium theories and it was seen that theory and experiment could be reconciled using plausible parameters to specify the microstructures of the films. Thus it appears that the angular, spectral and polarization dependences of obliquely deposited films can be understood, at least approximately, in terms of conceptually simple theoretical models.

The effect of polydispersity on extinction cross sections is studied for a particle system composed of coated, spherical particles. Aden - Kerker equations, governing the light-scattering behaviour of the system, are formulated in a way that makes them more suitable for computation purposes. Differences found between light scattered by non-absorbing and highly absorbing particles show the importance of using accurate refractive indices, especially when dealing with their imaginary part, which accounts for absorption.

A hydrodynamic model for electrical arc modelling is used to study the interaction between the electrical arc and the sidewall in a low-voltage circuit breaker. The interaction model is based on an energy balance at the boundary. Comparisons of pressure, arc voltage and ablated mass between computations and experiments validate the model. The results confirm that the main mechanism at the sidewall is the photo-ablation. The model shows that, very rapidly, plastic vapours replace the air in the circuit breaker and are responsible for a residual conduction in the arc initiation region.

multilayers on Si(100) were prepared by ion-beam sputter deposition. By using a grazing incidence x-ray reflectivity technique, the layer thickness and interfacial roughness of the multilayers were quantitatively characterized. In particular, the differences in structural features between the on interface and the on interface, as well as the possible inhomogeneity of the layers, were successfully revealed. The x-ray reflectivity results are consistent with the high-resolution electron microscopy observations. The process of the growth of the multilayers is also discussed.

The exceptional properties of aluminium nitride make this material a very promising candidate for a variety of technological applications. In this paper we report our work on the preparation of thin films of aluminium nitride by reactive DC and RF magnetron sputtering. The physical and electrical properties of the films were studied as a function of the preparation conditions: concentration of nitrogen in the reactive gas mixture, the substrate temperature, the plasma power and the horizontal distance from the centre of the target. X-ray diffraction data indicated that highly oriented polycrystalline films could be fabricated. Rutherford backscattering and nuclear reaction analysis showed that nearly stoichiometric films could be prepared using nitrogen concentrations greater than 50%. For the DC plasma process, bombardment of the growing film plays a very significant role. The film growth mechanism was found to be very different for the RF plasma. The nuclear analysis of the films prepared at different lateral distances, together with measurements of the substrate potential, permitted modelling of the film formation process for both the DC and RF plasmas.

In this study the material properties of In-rich (> 28 at% In) thin films were evaluated and correlated against the device performance of completed devices. These absorber films were prepared by controlled selenization of Cu/In/Cu metallic alloys in an atmosphere containing and Ar. Transmission electron microscopy (TEM) indicated that these In-rich films consisted of small, highly defected (mainly stacking faults and microtwins) grains. The photoluminescence (PL) responses from these layers were dominated by three relatively broad emission lines (at 1.10, 0.975 and 0.89 eV) which were attributed to donor - acceptor pair transitions. Admittance spectroscopy measurements revealed the presence of deep hole traps close to the midgap position of these In-rich absorber films. These deep levels were observed in all our highly In-rich films and are believed to be detrimental to device operation. Quantum-efficiency measurements revealed two distinct long-wavelength cut-off points (at approximately 1000 and 1200 nm) indicative of there being two different and parallel existing phases in these specific films. Completed devices displayed non-ideal I - V characteristics such as a cross over of dark and illuminated curves, strongly bias-dependent current collections and, in extreme cases, even ohmic-like behaviour when evaluated under air mass (AM) 1.5 conditions. However, this behaviour was a strongly intensity-related one and measurements under low illumination levels revealed a dramatic improvement in the device characteristics. This anomalous behaviour was confirmed by quantum-efficiency measurements to be a function of the illumination level and temperature. Under normal operating conditions in the dark (corresponding to a low intensity level) good carrier collection was observed. However, when the cells were light biased during measurements (or evaluated at low temperature) a dramatic drop in was observed. This phenomenon is ascribed to a breakdown in the electrical field required to ensure effective separation of photogenerated electron - hole pairs.

Ultra-fine grain structures were obtained in soft Co-based amorphous alloys subjected to suitable heat treatments within a restricted range of temperatures which begins well below the conventional crystallization temperature, , of the alloy. These structures lead to superior soft magnetic properties and consist of magnetic nanocrystallites with an average grain size in the range 10 - 12 nm embedded within a residual ferromagnetic amorphous matrix. The results refer to amorphous ribbons of Vitrovac 6025, which were obtained by the single-roller quenching technique and had the nominal composition . With regard to the coercive field and the initial reversible permeability, the best softening nanocrystallization effects occurred in toroidal samples heat treated for about half an hour at around . For the amorphous alloy, the nominal values of (the Curie temperature) and are 210 and , respectively. The results are interpreted on the basis of the random anisotropy model generalized to two-magnetic-phase systems.

In this paper, the `charge-relaxation model' proposed in our preceding paper as a scheme determining the impact charge is discussed in detail, especially for the case of an arbitrary initial charge. It is shown that the model explains well not only the `equilibrium charge' but also the `charging line' in terms of a proportional dependence of the impact charge on the initial charge. The comparison between the measured impact charge and the theoretical value shows that the measured value increases with increasing impact velocity and impact angle and has a value at saturation about 110% of that estimated by our non-empirical theory. In the case of impact charging between a conducting particle and metal plate, the charge relaxed completely. This could be explained in terms of the two-dimensional relaxation of charge on the particle surface. Discussion and experiments on the particle-size dependence of the maximum charge showed that the maximum charge was proportional to the particle size raised to the power 1.5.

The paper describes a method of measuring the force on an electrically conducting cylindrical rod moving on parallel rails. This is similar to the ball-bearing motor. A comparison of forces has been made on rods of aluminium, brass, carbon, copper, lead, mild steel and stainless steel. Hollow cylinders were also investigated. The results, together with contact voltage measurements, strongly support a thermal driving mechanism located in the mechanical contact regions.

The propagation of wide Gaussian-type light beams is analysed by means of angle-spectrum representation. It is shown that wave equations can be split into equations for amplitudes and angle-spectrum parameters. Furthermore, the equations for angle-spectrum parameters, separated from those for amplitudes, prove to be linear. This allows one to consider beam propagation, including diffraction effects and the multi-harmonic regime in a quadratic medium. In the framework of this approach, the evolution of the spectrum parameters reflects the focusing (de-focusing) character of beam propagation. By taking diffraction into consideration we are able to avoid the problems associated with a point-type focus. A canonical example is considered for comparison of the present approach with existing models.

It is proposed that standard micromechanical structures, such as torsional plates, cantilevers, doubly supported beams and drumheads, can be fitted with zone-plate reflectors to form low-loss, high-contact and high-speed optical switches. Such devices have many potential uses, including fibre-to-the-home applications. This paper focuses on the calculated properties of zone plates for plane-wave, point and Gaussian beam sources.

An inverse method based on the symbolic approach is proposed to determine the boundary condition in three-dimensional inverse heat conduction problems. This method uses symbols to represent the unknown boundary condition and then executes an implicit alternating-direction finite-difference method to calculate the temperature distribution. The calculated results are expressed explicitly as functions of the symbol of the undetermined boundary condition. Then, a set of linear equations is constructed from the comparison between the output symbolic temperature and the measured numerical temperature. Thus, the set of linear equations is solved through the linear least-squares error method and leads to the solution of the unknown boundary condition. Results from examples confirm that the proposed method is applicable in solving the three-dimensional inverse heat conduction problem. In the example problems, a temporally dependent and a spatially - temporally dependent boundary condition are used to demonstrate the procedure of the proposed method. In the first example, the temporally dependent boundary conduction, the result shows that only one-point measurement is needed to estimate the temporally dependent condition whether the measurement errors are considered or not. In the second problem, the four- and eight-point measurement methods are adopted to estimate the temporally - spatially dependent boundary condition. The result shows that only the four-point measurement is needed to estimate the surface temperature when measurement errors are neglected. When measurement errors are considered, the eight-point measurement is required in order to increase the congruence of the estimated results to the exact solutions.

The drift velocity of electrons in He - Xe mixtures is calculated using the two-term expansion of the electron energy distribution function in Legendre polynomials. Collisions of electrons with ground-state and excited atoms are considered, together with Coulomb collisions. The calculations are performed under conditions when negative differential conductivity of electrons occurs. It is shown that concurrent effects of Coulomb collisions and of electron collisions with excited Xe atoms extend the region of parameters in the He - Xe mixtures where negative differential conductivity takes place.

Emission spectroscopy, optical actinometry and mass spectroscopy non-equilibrium plasma diagnostics have been applied for the determination of parameters of the low-pressure arc discharge with an evaporating graphite cathode in a methane atmosphere. The absolute density of hydrogen atoms and the relative concentration of CH radicals, as well as the degree of dissociation of hydrocarbon (x = 1 - 4) radicals have been determined as functions of the pressure of methane. The optical properties of the hydrocarbon films deposited by the discharge have been investigated. The results of the investigation show that the transmittance of these films is associated closely with the optical emission intensity ratio of the CH (430 nm) and (656.2 nm) spectral lines.

Pulsed electron-beam excitation of solid Ne films doped with 0.4 - 0.6% CsCl leads to fluorescence bands in the deep UV region. The strongest band at 220.1 nm (FWHM 13 nm) is assigned to the transition and a much weaker one at 249.2 nm (FWHM 15 nm) to the transition of the ions on the basis of transition energies (including dipole solvation) and line shapes. The 220.1 nm band provides a large cross section for stimulated emission of and the band intensity depends strongly on the CsCl content, with optimal values similar to that obtained for CsF. The homonuclear ) transition at 263.2 nm indicates that pre-dissociation occurs via the state.

In this paper, a new powder processing method is described. A layer of metal cobalt is successfully coated on the surface of fine and TiC powders by chemical deposition. The mixture of the two kinds of Co-coated powder (about 70 wt% wt% TiC - Co) is hot pressed into a fine (ATC) ceramic. Scanning electron microscopical observation is employed to investigate fracture sections and erosion surfaces. Comparing with AT30 (70 wt% wt% TiC) ceramic, its high fracture toughness and strength with relatively fine microstructure are believed to make it more resistant than AT30 ceramic against particle erosion under different impact velocity and impact angles. The SEM images show that the worn surface exhibits shallow detaching, microcracking and plastic deformation. Erosion wear resistance depends on not only mechanical properties, but also microstructure.

Single-crystal rods and fibres of of various sizes oriented along [100] direction were successfully produced by a floating-zone method. Each of these crystals has a purely orthorhombic structure and a clear Curie transition at (with a peak at ). Investigation of the growth characteristics revealed that the vaporization of is dependent on the quality of the source rod, the growth rate and the length of the molten zone. For a source rod of pure , a growth rate of and a sufficiently short molten zone (for example 1.7 - 2.0 mm for growth of a 2.8 - 3.2 mm diameter crystal), a good (transparent, without cracks or inclusions) single crystal can be produced directly from the stoichiometric source rod. Otherwise, a source rod with excess is necessary to compensate for the vaporization of during the growth process. The excess amount of required is dependent on the sintered state of the source rod, the growth rate and the phase structures of the original powders from which the source rod had been pressed. In general, an increase in growth rate or in sintering temperature can decrease the required excess amount of in the source rod. However, the excess amount of required can be dramatically decreased by making the source rod from and .

In this paper, we present quantitative data on the amplification behaviour of alternative imaging gases in environmental SEM and describe the experimental methods used to obtain them. We investigated the gases' amplification abilities over the pressure range 0 - 12 Torr with respect to the primary beam energy, detector gap distance and detector accelerating field, in order to isolate optimum imaging conditions for each gas. The gases investigated were, in addition to water vapour, nitrous oxide, carbon dioxide, nitrogen and helium.

Unfortunately a typographical error occurred in the above paper. Equation (12) should have read

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