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A free standing surface wire nanostructure defined on GaAs[001] containing a 5 nm thick GaInAs single quantum well (SQW) was analysed, recording reciprocal space maps by coplanar high-resolution x-ray diffraction (HRXRD) and non-coplanar x-ray grazing incidence diffraction (GID). We were able to evaluate the depth and the thickness of the SQW by depth resolved GID via computer simulations based on a kinematic approach. The identification of the SQW was possible exploiting the large scattering contrast between GaAs and GaInAs at the (200) in-plane Bragg reflection. For HRXRD the nearly rectangular shaped wires directed along [110] give the main contribution to the intensity map in reciprocal space whereas the SQW itself is not visible. This demonstrates that combined HRXRD and GID reciprocal space maps provide an entire 3D analysis of surface nanostructures.

Plasma technology is progressing rapidly, although there is still a need for much research and development. In situ diagnostics such as emission spectroscopy are set up to control the plasma processes. Two experiments concerning treatments of polymer and steel surfaces using a flowing post-discharge plasma of and are described. The diagnostics of O and N atom densities have been correlated to the surface activity (for the polymer) and to the coating formation (for steel). Poisoning of the glass tube walls of the flowing discharge and post-discharge reactors was achieved by introducing a little into or a little into . We observed a detectable increase in density of atoms of the dominant gas species in both cases.

A comparison of electron emission obtained from low-resistance diamond thin films with various surface morphologies was performed. The films were deposited on Mo using microwave-plasma-enhanced chemical vapour deposition techniques. Ball-like and cauliflower-like diamond films, characterized by the presence of some diamond grains on graphitic balls, had a surface resistance (3 K to 10 M ) than that of relatively smooth continuous diamond films (20 - 140 M ). For all types of films, the turn-on field increased with increased surface resistance. The mean emission current density of 1.8 mA at a field of 4.6 V was obtained from a ball-like diamond film with an emitting area of . This indicates that these low-resistance films with ball-like surface morphologies can be good field-electron emitters. Field enhancement due to a `projection on a projection' geometry could be a partial explanation of our results.

This paper applies the physics of a squeezed film between porous surfaces to the impression of an ink dot into paper. The models developed are implemented numerically via the finite-element method. When compared with observations reported in the literature, the models are shown to be capable of representing the effects of process parameters such as the pressure, viscosity, permeability and film thickness on the dot gain which is used frequently as a characteristic to measure printing quality.

The present work approaches the problem of determining, by analytical solutions, the electromagnetic field created by an arbitrary distribution of alternating currents placed outside an infinitely long non-magnetic conductive cylinder. Making use of the dyadic Green function method, the electromagnetic field outside the cylinder is expressed as the sum of the field in free space and the field created by the currents induced in the conductive cylinder. The general results we obtained are particularized for the analytical solutions describing the operation of an eddy current transducer with rotating magnetic field for the case of a conductive cylinder non-coaxial with the current source.

Measurements of the complex, frequency-dependent susceptibility, , of three colloidal suspensions of magnetite in isopar M (a hydrocarbon carrier) in the frequency range 30 MHz to 6 GHz for 14 values of the polarizing field, H, over the range 0 - 116 kA are presented. The effect of the polarizing field on the real and imaginary susceptibility profiles of the suspensions is clearly demonstrated and these measurements reveal the presence of a subsidiary loss peak in the component. This effect is found to exist over the approximate polarizing field range 9.5 - 40 kA and may be attributed to the presence of relatively strong high-frequency relaxation modes superimposed on the Néel relaxation mode, as originally predicted by Coffey et al and later analytically explained by Garanin. The dependence of this effect on the particle concentration is demonstrated.

Nanocomposite powders of -Fe phases are prepared by mechanical alloying. Starting from high-energy ball milling of elemental powders, mixed to give a nominal composition of , the hard phase is formed by a solid state reaction at relatively low temperatures and coexists with the bcc-Fe phase. For an optimum annealing temperature, this two-phase composite material shows remanence values well above 0.8 T and a very smooth hysteresis loop that is typical for a magnetically single-phase material. This has to be attributed to a strong exchange interaction between the soft and the hard grains. In order to improve the magnetic performance, the influence of several additions on the microstructure has been studied. This enables us to explain the different magnetic properties of Si, Zr or Cu containing samples.

In the welding of metal sheets by lasers or electric arcs, a problem of considerable interest and importance is the formation of stresses and strains in the material undergoing the welding process. This paper investigates the process making use of the linear theory of elasticity. The non-uniform heating of the metal is allowed for by the presence of an appropriate term in the stress tensor representing the temperature field. The weld pool is approximated by an elliptic region which is constant in cross sectional shape with depth. This paper calculates the stresses in metal outside the molten region in the frame of the laser using mainly analytical techniques and in its final stages evaluates these numerically for the cases of an unclamped as well as a clamped metal sheet. The results are found to be largely independent of the particular metal when the stresses are expressed in dimensionless form. The effects of welding the metal with a laser are essentially reversible in character when the analysis is restricted to linear elastic theory without phase changes.

Periodic arrays of discharge tubes placed directly against each other were used to produce a plasma layer scattering and absorbing electromagnetic waves. Reflection, transmission and absorption factors of normally incident waves were studied both theoretically and experimentally for these arrays in the frequency range 5 - 12 GHz. Two wave polarizations were under investigation; the electric field of the wave was either parallel (E wave) or perpendicular (H wave) to the tube axis. Glass tubes with inner diameters 1.3 - 1.4 cm were filled with an Ar - Hg mixture or Xe at a pressure of several Torr. The plasma density on the tube axis varied in the range - . The results of calculations fitted the experimental data well. Better reflection can be achieved for E waves when employing tubes with a lower permittivity. From the point of view of better absorption it is preferable to deal with the H wave, for which resonant absorption dominates. Only a weak dependence of reflection, transmission and absorption factors on the tube wall permittivity and electron collision frequency held in this case. Power consumptions required to sustain plasmas with equal density in the tubes filled with Xe appeared to be smaller than those for the Ar - Hg mixture by a factor of about three.

This paper presents a theoretical analysis of the nitrogen afterglow induced by a microwave discharge in and - Ar. The initial conditions at the beginning of the afterglow are obtained by solving the electron Boltzmann equation, under the effective field approximation, coupled to the rate-balance equations for the ) levels, the electronically excited states of , the atoms and the main positive ions. The electric field for the maintenance of the discharge is self-consistently determined. Once the concentrations of heavy species in the discharge have been obtained, the relaxation in the afterglow of the above system of equations is investigated. It is shown that, as a result of the mechanisms leading to associative ionization by collisions between the electronic metastable species and , associated with the near-resonant V - E energy-exchange reaction , the characteristic emission of the system of can occur in the afterglow of a microwave discharge at p = 2 Torr after a time s. However, in the case of - Ar mixtures the state arises only for higher pressures and longer residence times (such as - s in a - 50% Ar mixture at p = 10 Torr). The predicted dependences on the pressure and gas-mixture composition of the temporal evolutions of [] and [] concentrations are shown to be in qualitative agreement with reported spectroscopic measurements.

The energy dependent albedo problem of low-energy light ions from heavy targets is considered in a multiple-collision model. The ion transport equation is treated with the assumptions that (i) the distribution function is almost isotropic and (ii) the transport cross section depends only on initial ion energy. The transport equation is Laplace transformed in relative path length and solved by applying the DP0 flux approximation in angle. Reflected energy spectra, particle and energy reflection coefficients are analytically derived. A comparison of DP0 results with age theory, computer simulation data and experimental results is made.

thin films were deposited by a sol - gel process onto various substrates without lattice match and their preferred orientations were investigated. Preferentially a axis-oriented films were obtained on Si(111) and quartz glass. The films on r-sapphire exhibited a highly preferred orientation along both the (101) and the (110) axes. Both a and c axis-oriented thin films were prepared on (111) Pt-coated Si substrates. It is demonstrated that the films fired at lower temperatures are difficult to align with the substrates. The degree of grain orientation of thicker films is lower than that of thin films. The origin of the orientations found in our thin films is discussed. However, the mechanism by which nuclei of the orientations form at the film/substrate interface is not yet known.

The common assumptions for closure of the first three moment equations with non-parabolic band structure have led to many inconsistencies associated with the electron temperature, effective mass and heat flux. The assumptions are involved in the heat flux based on the Fourier law and in the electron temperature determined from the average kinetic and drift energies. The inconsistencies resulting from these assumptions are studied and illustrated for electrons in silicon with a non-parabolic energy band. A simple alternative by means of which to avoid the inconsistent assumptions and to truncate the hierarchy of the hydrodynamic equations with non-parabolic band structure is proposed. Instead of using the Fourier-law heat flux to close the hydrodynamic equations, the energy flux is separated into fluxes carried by average and random velocities. The proposed model and a Fourier-law-based hydrodynamic model, together with the Monte Carlo method, are applied to a silicon sub-micrometre - n - diode with a non-parabolic band at various applied voltages. Effects on electron transport in the sub-micrometre device resulting from the assumptions of the Fourier-law heat flux and the electron temperature determined from the average kinetic and drift energies are investigated.

An equivalent circuit model for the unloaded piezoelectric vibrator in the thickness mode is presented. The model contains two branches, the motional branch and the static branch, like the lossless resonator model, but the circuit elements are generalized by making each a complex constant. The mechanical, dielectric and piezoelectric losses associated with the vibrator are accounted for by the imaginary components of the circuit elements. The model produced impedance curves that closely matched the impedance calculated by using equations derived from vibration theory and the data measured for lead zirconate titanate and PVDF - TRFE co-polymer samples. The calculation of the circuit parameters from the complex elastic, dielectric and piezoelectric material constants is straightforward and the model accurately fits both the baseline dielectric behaviour and the piezoelectric resonance around and below the fundamental resonance. Conversely, when the complex circuit parameters are known, the complex material constants can be derived by straightforward calculations without any loss of information.

Heterostructure multilayer thin films of electroactive polymers such as protonated poly(p-pyridyl vinylene) (PHPyV) and sulphonated polyaniline (SPAn) have been fabricated via processes based on the spontaneous self-assembly of conjugated poly-ions on to a substrate. The heterostructure thin films formed from these polymers exhibited a perfectly linear relationship between the absorbance and the number of SPAn/PHPyV bilayers deposited. A greenish - yellow electroluminescent (EL) diode utilizing a SPAn/PHPyV multilayer thin film has been fabricated and the EL properties of this device are discussed. The EL emission of this device can be qualitatively interpreted in terms of radiative recombination of the singlet polaron exciton formed by the injection of electrons and holes. The EL intensity of this light-emitting diode is weak. This result is discussed in terms of the quenching centre of cationic sites on the PHPyV polymer's main chain at the heterojunction. The Stokes shift due to the absorption and emission of a phonon is clearly observed in the EL spectrum of this device. A small shift between the EL and PL spectra of SPAn/PHPyV is observed. It was assumed that the EL emission takes place in a narrow region at the interface whereas the PL emission probes the bulk of the film. The SPAn/PHPyV monolayer LED emits yellow light, but the SPAn/PHPyV multilayer LED emits greenish - yellow light and there is a slight shift between the two spectra of these devices. These results can be interpreted in terms of the effect of confinement of carriers in the superlattice structure constituting the SPAn/PHPyV multilayer system.