Table of contents

In magnetron sputtering systems it is known that, due to the presence of a non-uniform magnetic field distribution, neither the erosion of the cathode nor the optical emission of the discharge are uniform. In this work, the magnetic field distribution near a magnetron cathode is measured experimentally and fitted by means of a convenient mathematical expression. The experimental spectroscopic optical tomography of the discharge is performed during the sputtering process, while the erosion profile of the cathode is measured after sputtering. It appears that there is a correlation between these measurements. In order to explain these results, the equations of motion of the electrons are solved numerically for the case of the fitted magnetic field distribution, plus a non-uniform electric field. The zone for confinement of electrons near the cathode is seen to be in accordance with the experimental data.

Orientation and purification of carbon nanotubes have been demonstrated using ac electrophoresis in isopropyl alcohol. Nanotubes move towards the electrodes for all frequencies of applied electric field from 10 Hz to 10 MHz. However, carbon particles contained as impurites become harder to move with increasing frequency. The degree of orientation of nanotubes is higher when the frequency is higher and nanotubes are longer.

An unusual interlayer coupling, recently discovered in layered magnetic systems, is analysed from the experimental and theoretical points of view. This coupling favours the orientation of the magnetization of the adjacent magnetic films. It can be phenomenologically described by a term in the energy expression, which is biquadratic with respect to the magnetizations of the two films. The main experimental findings, as well as the theoretical models, explaining the phenomenon are discussed.

ZnO films were grown on interdigital transducer (IDT)/Corning 7059 glass substrates by RF planar magnetron sputtering using two-step fabrication methods for surface acoustic wave (SAW) applications. The crystalline structure of the as-deposited ZnO films was characterized by x-ray diffraction (XRD) and x-ray rocking curve analysis. The SAW properties, including coupling coefficient and insertion loss, were evaluated and compared with the theoretical results. ZnO films deposited by the two-step fabrication method exhibited a lower insertion loss and a closer agreement between the experimental coupling coefficients and the corresponding theoretical values in comparison with films deposited by the one-step fabrication method. The results could be useful in the design of high-coupling low-loss SAW devices.

Thin films of p-type doped polythiophene were found to react rapidly but irreversibly with ammonia and water, whereas the loss of conductivity was largely reversible by evacuation in p-type doped polypyrrole. The interaction between compensating agents such as ammonia and water with p-type doped polythiophene and polypyrrole has been examined and chemical reaction schemes have been proposed with the possibility of their use in sensing devices.

The electrorheology of a zeolite/silicone oil suspension with direct current (dc) and alternating current (ac) electric fields was determined at room temperature. The shear yield stress changed only slightly with the field frequency, but the current density increased considerably. Good agreement occurs between the experimental results and those predicted by our model for both the shear yield stress and the current density. This study shows that there is a significant electrorheological (ER) effect over a large frequency range when a suspension has both a high conductivity ratio and a high dielectric ratio of the particles to the host oil.

Thermo-magnetic studies combined with transmission electron microscopy of and amorphous and nanocrystalline alloys revealed the precipitation of a single BCC -Fe nanocrystalline phase during the first stage of crystallization and the formation of intermetallic phases, the growth of -Fe nanograins and further precipitation of -Fe nanograins from the residual amorphous phase during the second stage of crystallization. The presence of 1 at% Cu in the second alloy accelerates the precipitation of the single nanocrystalline phase during the first stage of crystallization and facilitates further precipitation of -Fe nanograins from the residual amorphous phase during the second stage of crystallization.

The paper deals with the signal processing of ultrasonic pulses in absorptive and dispersive solids. The linear theory based on the Fourier transform is applied to the study of ultrasonic wave propagation in the polymeric film strip. The spurious echoes stemming from wave reflection at the borders of the specimen can destroy part of the pulse. Two methods of analysis of partly destroyed signals are presented and compared using mathematical modelling of the ultrasonic pulse propagation in the material.

A retrospective heat conduction problem is to estimate the temperature distribution in the previous moment from measured temperature histories at fixed locations inside the body. This is an important problem because an accurate retrospective solution can be used to detect the cause of something abnormal in a manufacturing process or to set up an initial state for a thermal process with required characteristics. In this research, a reverse matrix method is used to estimate the previous state in a two-dimensional heat conduction problem. Two kinds of retrospective problems are studied in this paper: one is to estimate a previous state at the time when the measurement starts and the other at the time before the measurement starts. Comparisons between the exact state and the estimated ones are made in order to confirm the validity of the proposed method. The close agreement between the exact solutions and the estimated results shows the potential of the proposed method for finding the accurate value of the retrospective solution in the heat conduction problem.

Tomographic equations for the velocity and temperature of heavy particles in plasma have been derived using the relations of the velocity distributions with the Doppler shift and broadening of the spectral lines. These equations are correct for non-Maxwellian velocity distributions and for arbitrary plasma flow. This approach was used for the computation of ion velocity and temperature radial distributions from the spectroscopic data in a highly ionized plasma centrifuge. Separation factors of 15 for Ar-Kr and 22 for Ar-Xe mixtures with a density of are obtained.

Some recent results indicate that the electronic current emitted by the cathode of a high-pressure electric arc may be enhanced by very close positive ions. This problem is addressed here by means of a 2D treatment of the Schrödinger equation, based on a finite element method. In addition, a diagonalization method has been implemented to study the specific role played by processes of electronic resonance. This approach is applied to the test case of an ionized hydrogen plasma in front of a copper cathode. By comparison with a previous 1D study, the present predictions show that a full 2D treatment is required in most cases.

Although the density of dislocations is used as an indicator of the quality of semiconductor wafers, it is also necessary to provide a description of the dislocation distribution for those materials prone to polygonization (namely the formation of sub-grain boundaries). In this work it is shown that visual inspection of etch pit distributions is insufficient and that quantitative comparison with random distributions is more informative. This was achieved in two ways: (i) by comparison with a Poisson distribution and (ii) by using normalized radial dislocation density plots, the former yielding the type of distribution and the latter the characteristic sub-grain tilting angle for the sample. Although these methods are general, examples for melt- and vapour-grown CdTe and (Cd, Zn)Te are given. Also reported upon in this work is the use of etching solutions to reveal inclusions in CdTe and (Cd, Zn)Te and hence permit their chemical identification by SEM/EDAX.