Table of contents

The general concepts governing the electrochemical deposition of metal films onto semiconductors are discussed. Deposition onto semiconductor surfaces is complicated due to the band structure of the semiconductor, which affects both the thermodynamics and the kinetics of metal deposition processes. The influence of the potential distribution at the semiconductor/solution interface on the charge transfer mechanisms involved in deposition of metals is discussed. Models for electrochemical nucleation and growth are described and the influence of the unique physical properties of semiconductors is analysed. Finally, we present recent results for electrochemical deposition of gold, copper and platinum onto n-type silicon.

Heat transfer over a stretching surface with variable surface heat flux and uniform surface heat flux subject to injection and suction is examined. The boundary layer equations are transformed to ordinary differential equations, containing an injection parameter I, velocity exponent parameter M, heat flux exponent parameter and Prandtl number . The effect of these parameters is studied. Suction increases the heat transfer from the surface, whereas injection causes a decrease in the heat transfer.

The tribological characteristics of diamond-like carbon (DLC) films have been studied by lateral force microscopy (LFM). Specimens from two fabrication routes, ion-beam assisted deposition and chemical vapour deposition, have been investigated. Thick (micrometres) and thin (a few nanometres) films from both routes have been considered, as have the service environments of ambient air and vacuum. Lateral force data were calculated from `friction loops', obtained as functions of load, surface topography, scan speed and service environment. An identical methodology and LFM probe were used throughout the series of measurements in order to ensure internal consistency, and the validity of the methodology was checked against measurements on epitaxially grown Si. A linear dependence was observed between lateral force and force loading up to ca , in accord with a multi-asperity model, thus allowing determination of coefficients of friction that ranged from 0.05 to 0.15. The results showed that adhesive interactions contributed up to to the overall dynamic load. Meniscus interaction played a minor role in comparison to that from tribo-generated electrostatic forces. The experiments show that LFM methodologies have value and relevance to the science and technology of tribology, especially when the required spatial resolution cannot be obtained with the traditional macroscopic techniques.

The surface tension of detached liquid drops in pulsed gas metal arc welding was determined in situ from the period of the prolate-oblate oscillations initiated by the detachment event. The oscillating drops were imaged by an optical shadowgraph technique utilizing laser illumination. Images obtained during the welding process were recorded with a high-speed video camera and stored for subsequent analysis. For 4047 aluminium alloy wire, surface tension values in the range 0.54-0.7 were obtained for various droplet sizes.

This work presents a novel three-intensity-measurement technique to determine the ellipsometric parameters and in a polarizer-sample-analyser photometric ellipsometer. This technique can be employed to correct the azimuthal misalignment of the analyser with respect to the plane of incidence. By performing two sets of measurements with this technique with the polarizer's azimuth at and , respectively, we can simultaneously determine the azimuthal deviation of the polarizer and further improve the ellipsometric measurements. Applying this technique in the transmission mode allows us to obtain the phase retardation and the optical axis of a waveplate at the same time.

In contrast to conventional methods of diamond chemical vapour deposition (CVD), nanocrystalline diamond CVD takes place with only a small fraction of feed gas hydrogen. Minimal amounts of , believed critical in hydrogen-rich CVD, are expected to be produced in hydrogen-deficient systems and alternative mechanisms for diamond growth must be considered. The carbon dimer, , is believed to be an important species in these growth environments. We have experimentally determined the density of gas phase in and microwave plasmas used to deposit nanocrystalline diamond. The density is monitored using high-sensitivity absorption spectroscopy of the (0, 0) band as chamber pressure, microwave power, substrate temperature and feed gas mixtures are varied for these two chemical systems. The absolute density of is most sensitive to the total chamber pressure and fraction of carbon in all molecular species in the feed gas in discharges and to the total chamber pressure and substrate temperature in plasmas. We discuss possible production channels in both chemical systems. The efficiency of production from fullerene precursors is over an order of magnitude greater than that from hydrocarbon precursors.

Among the thermoelectrical materials known so far, n-type semiconducting materials have a much higher thermoelectrical figure of merit ( Z) than do their p-type counterparts. This keeps the overall figure low for a couple at all temperatures. At room temperature the best Z is about in the Bi-Sb-Te system. At liquid nitrogen temperatures, a suitable composition can deliver and further improvement is possible with the application of a magnetic field. A combination of n-BiSb with a YBCO passive leg allows very high thermoelectrical power to be generated below for incident radiation. The photo-thermoelectrical bolometer's design is such that this power drives the charge carriers around a circuit fabricated from YBCO-BiSb elements. The YBCO leg is inductively linked via a closely positioned copper film coil and connected to a remote ac bridge and an electronic read-out system. A specific detectivity of and a response time of the order of milliseconds, controlled basically by the inductive property of the superconducting element and its resistance in the mixed state, should be easily achieved. This paper presents an ab initio analysis of the new thick bolometer with a responsivity of about .

The magnetic properties of 500 Å thick amorphous thin films with 0.16 < x < 0.35 have been studied experimentally. All films possess a strong perpendicular magnetic anisotropy (PMA) with an anisotropy constant . Using a polar Kerr microscope, the magnetic domain patterns in the samples with different values of the compositional parameter x were observed, revealing strong correlations between the domain shapes and the magnetic parameters of the films.

In order to explain the experimental observations a micromagnetic model of domain growth on a two-dimensional hexagonal grid is developed. By means of an FFT algorithm with periodic boundary conditions an adequate description of the demagnetizing field distribution was achieved. The model allows us to calculate both the domain patterns and the hysteresis loops, showing good agreement with the experimental observations. Both the experimental and the theoretical studies demonstrate that the closeness to the compensation point is the decisive factor controlling the micromagnetic behaviour of the films.

For the first time a microwave discharge located in the plasma of decaying optical breakdown of gas (air and argon at atmospheric pressure) has been generated. Four beams (each with a power of up to 100 kW) were injected sequentially into a volume of ionized rarefied gas which had been generated before hand by -laser radiation. The absorption was 50%, the maximum duration of the interaction of the microwave radiation with the plasma was 0.3-2 ms and was limited by the process of turbulent cooling. Depending on the parameters of the absorbing medium and microwave radiation a semi-self-maintained or self-maintained discharge with a diffusion or spark structure has been generated. A model for the calculation of basic characteristics of the decaying optical breakdown of a microwave discharge in it was suggested.

Two-photon laser-induced fluorescence (LIF) is used to study the production and loss of H atoms in a pulsed microwave discharge in over the pressure range 1-50 Torr. Absolute measurements of the H atom density are made at the end of the pulse. These measurements were calibrated using a new technique based on the decay rate of the LIF signal. The temporal variation of emission during pulsing of the discharge is used to estimate the rate of dissociation of , which compares well with the predictions of a one-dimensional model for the electron energy distribution function. This measurement also gives the wall recombination probability for H atoms, which is compared with that obtained by LIF measurement of the decay of the H atom density in the pulse afterglow.

A compact and simple type of current driver based on a plasma focus working in the mode of a plasma opening switch was used for excitation of a capillary discharge in Ar pressures in the range 0.1-0.5 Torr. A current of up to 50-60 kA with a rise time of about 200 ns was achieved in the capillary. The Ar plasma was compressed from an initial diameter of 5 mm to a diameter of 1 mm. The dynamics of compression have been studied using time-resolved VUV pin-hole diagnostics. Time-resolved VUV spectra show that the plasma consists mainly of the Ne- and F-like ions Ar IX and Ar X. A spectral line at 468.7 Å, which was identified as the transition in Ne-like Ar IX, has an anomalously high intensity compared with other 3-3 transitions of Ar IX.

By employing a movable retarding field analyser, ion energy distribution (IED) functions have been measured in a large-area microwave plasma at pressure, ranging from 0.3 to 0.8 mbar which are typical for the use of this plasma source. It can be shown that the IED functions are fully developed with decreasing exponential shapes. For a given microwave power, the IED function extends towards higher energies with increasing pressure. The mean ion energy also increases with increasing pressure and decreases with increasing distance from the active plasma region. The relationships between microwave power and mean ion energy are complex, but it is clear that the influence of microwave power on the IED and mean ion energy decreases at lower pressures and larger distances from the active plasma region. The mean ion energy near the active plasma region decreases strongly with the distance from the centre of the microwave coupling window and this implicitly shows that the plasma possesses a strongly inhomogeneous internal field structure in this direction.

The composition and thermodynamic properties of products of the reaction were determined for the values of parameters , and in the pressure range 0.1-10 MPa and the temperature range 298.15-50 000 K. Reaction products for lower temperatures in the region considered form an ideal heterogeneous system in the state of thermodynamic equilibrium at constant temperature and pressure. The properties of a heterogeneous system are affected by phase transitions in the system and therefore attention is paid to the occurrence of condensed phases in the system in dependence on temperature, pressure and values of the parameters , and . The results are compared with data published so far by other authors, who usually assume that the system of products is gaseous. Among the many thermodynamic properties, the values of the specific heat capacity at constant pressure are given in particular.

A single-point magnetic resonance imaging study of water freezing in saturated and non-saturated porous materials is presented. Relevant considerations about relaxation time mapping in short relaxation time systems ( of tens to hundreds of microseconds) are discussed and results in concrete and mortar samples under cooling conditions are shown. A spatially resolved estimation of the occupied pore size distribution is achieved in specimens presenting short relaxation times. To the best of our knowledge, this is the first report on the effective determination of spatially resolved pore size distribution of intact concrete materials. Evolution of one-dimensional images as a function of temperature is qualitatively compared with a series of differential scanning calorimetry experiments for cement pastes conditioned under controlled humidity. No supercooling effect is observed in a water saturated concrete single-point imaging experiment.

A simplified version of the Williams-Watts relaxation model has been applied to interpret thermally stimulated polarization (TSP) currents obtained in dye doped polystyrene. The system showed the and relaxation processes typically observed in polymers, but the amount attributed to each process changed from experiment to experiment. However, this peculiar behaviour has been matched by changing and content parameters as allowed by the model. In order to help in the fitting, some parameters were tentatively derived from isothermal current decay experiments, but they did not provide a good fitting in the region. Improvement obtained by relaxing the above-mentioned condition seems to imply that even near the glass transition temperature the guest dye molecules were not under thermal equilibrium in the TSP experiments probably due to the large size of the molecules. The concept of intrinsic time was used in order to describe a non-isothermal process.

The space charge characteristics in cross-linking polyethylene (LPE) are investigated under various electrical stresses from dc to power frequency. The pulsed electro-acoustic method is improved to meet the needs of measurement under ac voltages. The frequency and phase angle dependences of the space charge are studied by means of phase-locking and frequency-converting techniques. Test results show that space charge can develop and accumulate in LPE under an ultralow frequency voltage. The critical frequency of the applied ac voltage is less than 0.02 Hz. The mechanism of the formation of space charge in LPE under an ac voltage is discussed through degassing of a sample in vacuum.

Temperature lags between the heating element and the sample are known to exists during a thermoluminescence measurement. The experimental difficulties associated with the temperature lag can be quite serious, when one wants to extract physical information from the glow curves, because it is obviously essential to know the sample's temperature rather than that of the heating element. In the present work approximate relations to estimate the temperature lag between the heating element and the dosemeter and the effective heating rate across the sample are proposed. Preliminary experimental tests of the proposed equations are performed on LiF:Mg, Ti and and on data taken from the literature.

The general order kinetics expression of thermoluminescence (TL) contains two empirical parameters, namely the kinetics order (KO) and the pre-exponential factor (PF). In this paper thermoluminescence glow curves are calculated by assuming well defined physically meaningful models and the KO and the PF values applicable to these glow curves are calculated. The approaches used to find these values are either analytical or based on the shape of the glow curves or their isothermal decay behaviour depending on the type of the model used. The results show that the KO and the PF parameters are in general not constant for a given glow peak. They vary with the change in occupancy of the traps except under the two limiting conditions, namely KO equal to 1 or 2. This means that, when the KO of a given glow peak is not equal to either 1 or 2, its numerical value as well as that of the PF would depend on the sample dose. It also means that these parameters change continuously when the glow curve is being recorded. At very low trap occupancies these parameters approach limiting values. For the simple one-trap model this limiting value of KO is 2 whereas that for a multi-trap model is 1. The corresponding changes in the quantitative values of the PF are by large orders of magnitude and the variation is in the direction opposite to that of the KO. Furthermore, the dimensions for the PF also change. These results bring the general order kinetics approach into conflict with the physical models used to describe the TL glow curves. Implications of these theoretical results for experimental observations are discussed.