Table of contents

A treatment is given using asymptotic matching techniques of the boundary between an active collisional plasma and a collisional sheath. This shows that the one joins smoothly with the other and that it is not appropriate to talk of a modified Bohm criterion in this physical situation.

The density of interface states at the epitaxial - Si(111) interface grown under UHV conditions at 700 is found to be much lower than assumed previously, as revealed from photoelectron spectroscopy. An upper limit is estimated to be near midgap, which comes close to values obtained for - Si interfaces.

Optical emission studies of molecules in plasma obtained by Nd:YAG laser ablation of graphite in a helium atmosphere are reported for irradiances in the range (1 - . The characteristics of the spectral emission intensity from the (Swan band) species have been investigated as functions of the distance from the target, ambient pressure and laser irradiance. Estimates of vibrational temperatures of species under various irradiance conditions are made. Results of measurements performed under different ambient helium gas pressures are also discussed.

The surface force apparatus (SFA) comprises thin molecularly smooth mica sheets glued to glass cylinders, which are pressed into contact with their axes at right angles. It is frequently used, in conjunction with the Johnson - Kendall - Roberts (JKR) adhesion theory, to extract the surface energy of the contacting sheets. This procedure is open to possible error since the JKR theory is based on the contact of homogeneous, isotropic elastic cylinders. This paper extends the JKR theory to the layered structure of the SFA. Two approaches have been followed: (i) direct calculations for prescribed values of the layer thickness and elastic moduli; (ii) an experimental calibration procedure for an existing apparatus.

Fluorinated silicon oxide (SiOF) films were prepared by plasma enhanced chemical vapour deposition (PECVD) and studied by FTIR spectroscopic measurements. As fluorination dosage increased, the band intensity of the Si - F stretching mode was observed to increase but the peak frequency and band width remained unchanged. The Si - O vibrational bands were found to increase in frequency and decrease in band width. The Si - O asymmetric stretching band was analysed. It was found that the average bond angle of Si - O - Si bond increased but the distribution of the bond angles decreased in width as fluorination dosage was increased.

The secondary reaction of HCl with the growing metal oxide surface during atomic layer deposition from a metal chloride and water is investigated using model calculations. HCl released during chemisorption of a metal chloride occupies adsorption sites for the metal chloride which results in a decrease in the film thickness in the gas-flow direction. The calculation model based on the continuity equation and kinetic equations for the surface coverage is described. The dependences of the thickness profile on the reactivity of HCl and on the adsorption of the metal chloride are analysed.

Cu - W multilayered films were properly designed according to an interfacial free-energy estimation such that an amorphous and three metastable crystalline FCC phases were formed by solid-state reaction in this immiscible system. To understand such alloying behaviour, a Gibbs free-energy diagram of the system was constructed on the basis of Miedema's model and related methods. The calculated diagram showed that the interfacial free energy resulting from chemical and elastic contributions could raise the initial energetic state of the multilayered films to a state higher than those of the observed metastable phases, thus providing a driving force for solid-state alloying in this immiscible Cu - W system.

The writing and reading processes of acoustic waves in Ni - Co polycrystalline ferrite have been investigated experimentally. Experimental dependences between the memory signal and input signals are presented both for read-in and read-out operating modes. A qualitative model is suggested for the writing and reading processes. Optimum operating signal levels were chosen in view of the use of memory phenomenon in magnetoelastic storage correlators.

Energy transfer between highly vibrationally excited CO molecules and low-energy electrons is studied using kinetic modeling. The results are compared with those of experimental measurements in optically pumped CO. The effect of vibrational energy transfer by electrons from the high towards the low vibrational levels of CO, previously observed in the experiments, is reproduced in calculations. The best agreement with the experiment is obtained for an electron concentration in the plasma of , which is consistent with the previous measurements of the vibrationally stimulated ionization rate. The results of kinetic modelling calculations provide better insight into the kinetics of energy exchange between vibrationally excited molecules and electrons.

Results related to the energy transfer in the rare gas mixtures are reported for an electrical discharge excitation with plasma expansion and a heavy-ion-beam excitation. Energy transfer from the lighter rare gases to the heavier ones was observed in a very efficient way for both excitation mechanisms. Strong emission from excited atomic states, which are possible candidates for new lasers, was observed for the electrical discharge case. The broad-band emission of the discharge sources makes them appropriate for strong lamps in the VUV. Some comparisons of the two excitation mechanisms were discussed with respect to the energy deposition, the density of dimers and their vibrational relaxation.

We have determined the electron temperature for the afterglow period of a high-voltage pulsed discharge in caesium vapours from the continuum radiative recombination spectrum. This spectroscopic method, successfully used for continuum current discharges, was adapted to our transient plasma conditions. Using a variable gate recording system, we determined the electron temperature to be about K in the early afterglow.

An electromagnetic particle-in-cell simulation code is used to study the mechanism of nonlinear amplification of inverse Bremsstrahlung electron acceleration. We find that the self-consistent space-charge field decreases only slightly the net energy gain. Previous results from single-particle or approximated self-field calculations are recovered in the appropriate limits. Furthermore, the simulation has also shown that, if the particles are launched into the interaction region as a pre-bunched particle beam, the average energy gain of the beam becomes much larger than that obtained when the particles are uniformly distributed along the laser wavelength .

This article presents an experimental study that contributes to the problem of interpretation of cylindrical Langmuir probe data obtained in a non-isothermal low-temperature plasma in magnetic field. A discussion on the influence of positive ion - neutral collisions on the charged particle density estimation is also given and the effect is demonstrated on the experimental data. A Maxwellian electron energy distribution is assumed throughout the present study. The Langmuir probe data are obtained in a cylindrical magnetron discharge in argon at pressures from 1.5 to 6 Pa and magnetic fields between 100 and 500 G. The radially movable Langmuir probe was made of either m or m diameter tungsten wire in order to investigate the effect of the probe dimensions on the estimated plasma density. The electron density is calculated from the electron current at the space potential (used as a reference) and from the OML collisionless theory. The ion density is calculated by using ABR - Chen theory without and with the correction due to the collisions of positive ions in the probe sheath. Also, the recent collisional positive-ion-collection-theory is used for comparison. The resulting numerical values of plasma density are compared over more than one order of magnitude change in the plasma density given by its radial dependence in the cylindrical magnetron discharge. Optical measurements were made in order to quantitatively assess the neutral gas temperature in the discharge and the density of particles in excited states that could induce secondary electron emission from the probe surface and thus apparently enhance the positive-ion density estimated from the probe positive-ion current.

The effect of secondary electron emission from the probe surface on the probe data interpretation has been found small compared to the experimental error limits and consequently not substantial for our experimental conditions. In the range of our experimental conditions the ABR - Chen theory with the collisional correction gives the best agreement of the estimated numerical values of ion and electron densities in the whole range of its investigated change. Also from our results it follows that the effect of the magnetic field on the thinner-probe-electron-current at the space potential and hence on the reference-electron-density-estimation is negligible within the experimental uncertainties up to a magnetic field strength of 500 G which was the maximum used in our experimental study.

The spatial and temporal ionization growth of pre-breakdown discharges in is compared with that in . The spatial growth of the ionization current shows differences which are attributable to differences in secondary-ionization processes caused by metastable-particle activity. The secondary processes are less efficient in than they are in . This is consistent with a previous suggestion (Fewell et al 1996 Chem. Phys. 206 257-67) that diffusion not only of the first electronically excited state but also of highly vibrationally excited electronic ground states of the nitrogen molecule plays a significant role in pre-breakdown discharges through nitrogen.

The temporal characteristics of 2D spatial images of the net excitation rate of argon in a low-pressure capacitively coupled plasma (CCP) reactor driven at high frequency (13.56 MHz) are investigated by computer-assisted optical emission tomography for pressures ranging from 10 mTorr to 1.0 Torr. The radial uniformity and sustaining mechanism of the CCP are discussed on the basis of the absolute net excitation rate of Ar() in Ar for 13.56 MHz.

Line widths and spin - spin relaxation times of P1 centres in synthetic Ib and natural Ia diamonds with concentrations of P1 and P2 centres covering the range 0.03 - 400 atomic parts per million have been measured. At concentrations higher than about ten atomic parts per million the line width is linearly dependent on the concentration. At lower concentrations the electron - dipolar contribution to the line width dominates and the width of the line remains constant. Since the pulse sequence employed for measurements eliminates the effects of inhomogeneous line broadening, of the line remains linearly dependent on the total paramagnetic impurity concentration, even at very low paramagnetic impurity concentrations.

We demonstrate the possibility of using x-ray photoemission spectroscopy (XPS) to distinguish between the chemical properties of the neuron membrane and of the cytoplasm in brain cells. This was possible by analysing cells de-capped by using a newly developed technique. The XPS spectra clearly show chemical differences between the cell cytoplasm and the membrane, for example between nitrogen in and , which are characteristic of the proteins and membrane phospholipids, respectively. A preliminary (and not conclusive) interpretation of all the observed spectroscopic features is given.

Samples of the system (x = 0, 0.1,..., 0.7) were prepared by the usual ceramic technique. IR absorption spectra were used for analysing the compositions. The AC conductivity and dielectric properties (loss tangent tan , dielectric constant and dielectric loss ) have been measured at various frequencies and temperatures. Three bands were observed in the IR spectra. The band at around and another one at around were assigned to the tetrahedral and octahedral complexes, respectively. A small band at around indicated the octahedral divalent metal-oxygen bond in these complexes. The threshold frequency for the electronic transition seems to increase with increasing content, namely with decreasing concentration.

At room temperature (RT), the AC conductivity exhibits dispersion in the frequency range from Hz to Hz. The variation of tan with frequency at RT shows a peak in the range Hz. The electrical conduction mechanism was explained in terms of the electron hopping model. Both effects (temperature and frequency) tend to increase and . The composition dependence of the dielectric properties is divided into two regions. The first one is for x<0.5 (for which long-range order is predominant) and the second one is for (for which short-range order is predominant).

Hafnium-substituted zirconium tin titanate dielectric ceramics with the general formula ( with x = 0, 0.05, 0.2, 0.4, 0.6, 0.8 and 1.0 have been synthesized by the conventional solid state ceramic route. The phase purity, crystal structure and microstructure of these compositions have been examined by powder x-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD analysis shows that ( undergoes a structural change as a function of x for x>0.6. The microwave dielectric resonator properties the dielectric constant , quality factor (Q) and temperature coefficient of the resonant frequency have been measured. The value is found to decrease with increasing Hf content. The elastic properties of these materials have been investigated by measuring their longitudinal and shear elastic modulii. Measurements of the temperature variation of the elastic modulii indicate that there might be a diffuse phase transformation in these materials above room temperature.

This paper discusses the stages of the curing process during the preparation of a polymer-network-dispersed liquid crystal from liquid crystal, methacrylate and dimethacrylate esters under UV irradiation. The morphology of each stage was measured by scanning electron microscopy. The effects of the irradiation time on the morphology are discussed. The relationship between the morphology of the polymer matrix and its electro-optical properties was investigated.

Models of fractally scaled, discrete-component, transmission lines consisting of resistors and capacitors have been investigated experimentally and computationally over extended frequency ranges. Agreement between the predicted performances of the lines and those measured has been found. In particular, a fractional power-law dispersion with frequency, which is a characteristic of scaling, has been observed in the form (, where p is defined by a fixed ratio of the logarithms of the scaling parameters. The effect of localized imperfections on the scaling has been examined by introducing errors into the scaling of the lines and determining the standard deviation of the exponent resulting from these defects. Both for increases and for decreases in magnitude, either of the resistive or of the capacitive elements, the limiting behaviour has been found to be characterized by a square-root dependence of the standard deviation introduced by the imperfection on the magnitude of the relative change in the component from the scaled value. The errors introduced into the dispersions are discussed in terms of the commonly observed fractional power-law response with frequency and the significance of variations from perfect scaling behaviour is discussed.