Table of contents

The effects of magnetic fields on electrons have been considered using the Boltzmann transport equation for a novel laser system-a magnetically confined gas laser. The equation has been solved numerically for CO₂ lasers, as an example in the study. Curves are presented of electron energy distributions and transport coefficients under the influence of a transverse magnetic field. An idea for improving gas laser efficiency has also been discussed.

The ablation of Al₂O₃ by CO₂ laser radiation is investigated both theoretically and experimentally. The model connects the laser-induced phase transition from condensed to vaporized state of the target and the dynamic of the emerging process plasma. The plasma is described in a two-fluid approximation by use of non-dissipative gas-dynamical equations incorporating absorption of laser radiation in the plasma and the dynamic of its ionization state. In the experimental part, the geometry of the luminous process plasma above the target at different instances is detected and the weight loss of the target as a function of the fluence is measured. At an Ar-base pressure below 1 mbar, both calculated and measured results reveal that there exist two zones in the process plasma: one which is directly attached to the target surface throughout the whole process, and another which is recognized as an outward moving shock front. Further, it is seen from both approaches that, due to absorption of laser radiation by the plasma, the weight loss has a local maximum.

Steady state stimulated Raman and Brillouin scattering gain coefficients have been calculated at various pressures of CH₄ and H₂ gases at a pump wavelength of 355 nm. The stimulated Brillouin scattering process dominates over the Raman scattering process at high pressure (0.5-10 MPa) of the gain media. This effect is stronger in CH₄ than in H₂.

The theory of stimulated Brillouin scattering in a ionized isotropic medium is developed. It is shown that if an electric field at a frequency of 2F, where F corresponds to the Brillouin shift, is applied to the scattered volume then amplification of the anti-Stokes component of the scattered wave takes place. The method of remote sensing of atmospheric aerosols is proposed.

Twelve theoretical models for the ultrasonic velocity in a system consisting of a solid matrix containing solid spherical inclusions have been compared with experimental data obtained from the literature. Four of the models failed to predict the experimentally observed minimum in the velocity-inclusion concentration curve, and can therefore only be considered suitable for low-concentration computations. All of the remaining models give qualitative agreement with the experimental systems considered and no one model is obviously superior to the others. There is a clear need for more high quality experimental data on solid-solid suspensions.

Thermal conductivity and thermal diffusivity of rock marbles have been measured between 290 and 335 K in dry air at atmospheric pressure using the TPS technique. X-ray diffraction has been carried out. Infrared spectroscopic studies identify various polyatomic anions of the type C0₃^2-, NO_3'^-, S0₄^2-, etc. The temperature coefficient of resistivity of the TPS sensor has also been determined over a wide temperature range. Thermal conductivities and thermal diffusivities do not change with change of heating currents at room temperature. Four of the five samples showed a slight increase in thermal conductivity with temperature but thermal conductivity of Sohabi White marble showed a decreasing trend with rise in temperature.

Optimal performance of endoreversible cycles is studied systematically based on another linear heat transfer law (the heat-flux q varies as Delta (1/T)) in irreversible thermodynamics instead of Newton's law. First, a fundamental optimum formula for endoreversible cycles is derived by using a three-heat-source cycle model. Then, the formula is used to deduce the performance bounds of various endoreversible cycles. Some new results are obtained. These results are compared with those obtained by using Newton's law. Consequently, the common characters and the main differences of an endoreversible cycle for the two linear heat transfer laws are expounded. Finally, the effect of finiteness of the high-temperature heat source on the optimal performance of an endoreversible cycle for the two linear heat transfer laws is discussed.

Considers the mathematical formulation for the macroscopic elastic properties of particulate media in terms of the distribution of the stiffnesses at the contacts between the constituent particles. Both random and regular arrays are considered. If the particles are sufficiently small the analysis leads to a relationship between the ensemble modulus and the surface energy of the solid particles. It has been previously suggested that, for random isotropic assemblies of spheres, this relationship could be predicted by a simple density scaling rule based on the solution for a simple cubic packing. The paper re-examines this analysis and identifies an inconsistency in the definition of the contact stiffness. An alternative analysis is also presented which is based on the solution for a body centred cubic packing. The new analysis suggests that the original theory overestimates the ensemble modulus and underpredicts the surface energy of the solid particles.

The transport properties of unexcited and excited electro-rheological (ER) fluid in combined Couette and Poiseuille flow are investigated. In particular the question of whether the fluid can be considered as a continuum with Bingham plastic constitutive properties, even though it is a two-phase solid-liquid mixture, is addressed. The hydrodynamic pressures generated using ER fluid in a Rayleigh step bearing at the limiting condition of zero net flow rate were measured. The properties exhibited by the fluid are compared with independently obtained data showing the continuum principle to be applicable to the flows examined.

The authors consider a low-pressure plasma column contained in a dielectric tube surrounded by vacuum and shielded by a metal enclosure. The plasma is sustained by a travelling, weakly damped electromagnetic dipolar wave. The metal shielding turns out to influence substantially the dispersion characteristics and hence the axial structure of the discharge in contrast to the case of azimuthally symmetric waves. Axial profiles of the electron number density and wave power have been calculated. A comparison with the available experimental data shows the significance of the non-uniform radial plasma density profile for this configuration, which is taken into account by replacing the actual electron-neutral collision frequency for momentum transfer by a greater effective value. It is determined by applying a scaling procedure (which is not a curve fitting) that refers to a single experimental point. Thus a very good agreement between theory and experiment has been obtained.

A theory and numerical model are proposed that explain the dependence of time delay on afterglow period, t_d=f( tau ) (the memory curve), for the Cu-N₂ system by surface-catalysed excitation at nitrogen atom recombination on the cathode. The kinetics in the late nitrogen afterglow are determined by nitrogen atom recombination. It is shown that the nitrogen atom recombination on the container walls (glass) is of second order in N (the recombination on copper is of first order). The probability of the metastable formation of N₂(A³ Sigma _u⁺) by recombination at the electrode surface is determined. The electron yield in the interelectrode space caused by metastable secondary emission (the Auger de-excitation process) determines the time delay. On the basis of this mechanism, the time-delay method is very efficient in detecting nitrogen atoms.

The ionization of calcium atoms resonantly excited to the 4s4p ³P₁ metastable state is investigated. In particular, the influence of various experimental parameters on the total ionization yield and the rate of its growth are reported. Maximum ionization yield was obtained with the buffer gas (Ar) pressure in the range 100-650 mbar. Furthermore, the time history of depopulation of the metastable state 4s4p ³P₁ monitored in a 'pump' and 'probe' experiment using a second dye laser tuned to the 4s4p ³P₁-4s5s ³S₁ transition is presented. The effective lifetime of the 4s4p ³P₁ state is shortened to 31+or-2 mu s at 850 degrees C and 800 mbar Ar pressure from the known value of about 350 mu s.

A pulsed atomic oxygen source, used to simulate oxidization mechanisms of spacecraft surface protective material (CASOAR), is probed by LIF. LIF measurements of oxygen atom density were first conducted in the post-discharge of an O₂ low-pressure microwave excited plasma. It appears that the fluorescence yield depends strongly on the laser beam focusing conditions. This dependence must be taken into account for proper analysis of the experiment. Thus, LIF measurements appear to be quantitatively correct and consistent with the results of NO₂ titration.

The results of an experimental investigation of a DC glow discharge in fast air flow at a pressure of up to two atmospheres are presented. A high efficiency in the production of chemically active particles is achieved in this kind of discharge. For dry air the ozone yield was as high as 80 g kWh^-1 at a concentration of 0.05%. The results of a successful application of this discharge for SO₂ and NO removal from polluted air are described. A full kinetic model for the glow discharge at atmospheric pressure of dry air has been developed which explains experimental results with satisfactory accuracy.

Models the positive column in strongly electronegative gases, where recombination is the dominant mechanism of charge loss in the volume. The pressure range is taken to be such that mobility governs particle motion. It is related to earlier work in gases like oxygen, where detachment is the dominant loss mechanism and there are many similarities with the case where the attachment/ionization rate ratio P was <1, treated by Daniels, Franklin and Snell (1990). It is shown that P is necessarily less than unity and that it is not physically possible to have a discharge where electron-ion recombination is the only loss mechanism. The structure found is that of a central positive ion-negative ion core surrounded by a conventional electron-positive ion plasma with a sharp transition region of fractional thickness given by the parameter l^1/2 where l is a normalized ratio of ion recombination rate beta _i and ionization rate nu _i given by beta _in_e0/ nu _i where n_e0 is the central electron density. Expressions are found for the ion plasma dimensions and the eigenvalue lambda , which relates the ionization rate, discharge radius, ion mobility and electron temperature, and comparison is made with the work of Volynets et al. (1993). The physical characteristics of such discharges are explained by the treatment given for the first time since the problem was formulated in 1949.

Threshold fluences for dielectric breakdown of pure CF₃H and a 0.8 ppm CF₃T in CF₃H mixture irradiated with pulsed infrared radiation from a CO₂ laser have been measured, allowing the effects of homogeneous pre-ionization resulting from beta decay of a tritium-doped gas on dielectric breakdown to be evaluated for the first time. In both CF₃H and the CF₃T/CF₃H mixture, breakdown occurs as a result of a cascade process from initiatory electrons present in the gas before radiation is applied. The pressure dependence of the breakdown thresholds suggests that recombination is a more important loss mechanism for the cascade electrons than is diffusion. At all pressures, the threshold measured in the presence of CF₃T was lower than that measured in pure CF₃H. However, in both pure CF₃H and the CF₃T/CF₃H mixture, the measured breakdown thresholds are well above the fluences required for laser isotope separation.

The radiation from active cathode spots in air and vacuum break arcs was investigated by different experimental techniques: streak camera recording, time-resolved and time-integrated spectroscopy. Spot rotation has been found with two frequencies omega ₁=2*10⁵ Hz and omega ₂=4-6*10⁷ Hz, and two characteristic radial velocities V₁=21 m s^-1 and V₂=130 m s^-1. From spectroscopic measurements, degeneration of the upper excited atom states is deduced, corresponding to a strong non-ideality of the cathode spot plasma with consequences for the particle density (N>10²⁸ m^-3).

The electrical power dissipation and the vibrational (v) and rotational-translational (RT) heating and cooling mechanisms in SiH₄-H₂ radio-frequency (RF) glow discharges are analysed. Detailed balance of the various contributions leads to determination of the steady state v and RT temperatures T_V and T_R depending on the discharge geometry, total and partial pressures, wall temperature and power density. In low-power SiH₄-dominated discharges (0.1-0.2 Torr range), v excitation is mostly due to low-energy electron-SiH₄ collisions, but in high-power discharges, dominated by H₂ (0.1-1 Torr), v excitation proceeds via collisional relaxation of hot H atoms and exothermic chemical reactions. v cooling is mostly controlled by v-RT transfer and thermal diffusion to the walls and by electron impact dissociation of v excited molecules. In any case the contribution of spontaneous decomposition highly v excited SiH₄ molecules (pyrolysis) remains negligible. The model is tested on various experimental situations and the computed values of T_V and T_R are in fair agreement with available measurements by IR emission spectroscopy and CARS. It is also shown that the spatial temperature profiles may induce thermophoresis on particulates generated within the discharge.

The coefficient of dissociative recombination of Ar₂⁺ ions at 300 K has been determined as (8.2+or-0.5)*10^-7 cm³ s^-1 by means of computer fitting of the rate equation with results of measurements of the absolute electron density in the afterglow. The present value compares well with previous data and gives insight into the temperature-dependence of the coefficient. The authors have developed a technique to determine two calibration factors of the microwave cavity, the geometrical factor K_d and the effect of deformation of the cavity field due to the presence of a glass envelope. The absolute number density of electrons has been determined using the calibrated microwave cavity. The calibration factors have been confirmed by Langmuir probe measurements.

Ingold's model (1978) for the medium pressure positive column is examined and compared with the original quasi-neutral theory of Self (1966). The model for cylindrical geometry is extended to plane and spherical cases, and their plasma balance equations (PBE) are further simplified without loss of accuracy. It is found that Ingold's model is inappropriate to predict the plasma density profiles, producing lower values than the exact curves. For helium plane and cylindrical positive columns, it is shown that the electron temperatures obtained from Ingold's and simplified PBES are accurate within several percent of the exact values and are in good agreement with reported observations.

In overdense HF or microwave induced plasmas a strong inhomogeneity of the maintaining electric field strength is usually found. From 'local' kinetic models, which usually employ the spatially homogeneous Boltzmann equation and assume that the electron distribution function is in equilibrium with the local electric field strength, an increase of the spectral emission towards the plasma boundary is predicted. In recent investigations, some contradictory experimental results have been found. Therefore a 'non-local' kinetic model is applied to this problem. In contrast to local models, in the non-local model the complete spatially inhomogeneous Boltzmann equation is solved so that the influence of the space charge potential and of the diffusive motion of electrons are taken into account. It is shown that the non-local model is capable of reproducing spatially resolved measurements of the spectral emission intensity much better than a local model.

The optogalvanic effect for the 1s₅-2p₂ transition (Paschen notation) in a low current (0.5 mu A) neon Townsend discharge has been studied for three pressures (1, 4 and 10 Torr). The optogalvanic effect occurs by irradiating the discharge with an expanded laser beam, in a variable plane parallel to the electrodes. By moving the discharge tube perpendicular to the electrodes and by using a dye laser with a continuously adjustable frequency, measurements of the optogalvanic effect could be carried out for a number of irradiation positions as a function of the laser frequency. In calculating the optogalvanic effect, secondary ionization processes are dominant and therefore one needs to know the probabilities that resonant photons and metastables produced in the discharge reach the cathode. The first probability has been calculated using Monte Carlo simulation methods, with the method developed by Lee to calculate the frequency redistribution of a resonant photon after the interaction with an atom. The second probability has been found by solving the transport equation of the metastables. The optogalvanic effect measurements agree to first order with the theoretical calculations.

Films of CdS_xSe_1-x with different x values (0<x<1.0) were deposited on glass substrates by co-evaporating CdS and CdSe using the two-zone hot wall technique. Films were highly resistive and polycrystalline in nature with partially depleted grains. Photoconductivity and dark conductivity of the films were measured in the temperature range 230-430 K. Data were analysed by utilizing the grain boundary trapping model with monovalent trapping states to determine the barrier height at the intercrystalline boundary. The variation of barrier height with intensity of the incident photons was studied.

The variation of photoconductivity with temperature and long-term photorelaxation under weak and moderate illuminations in polycrystalline InSe thin films are studied. Different decay characteristics are determined and it is found that separate barriers are responsible for drift and recombination. The long-term photodecay is found to be exponential with time for weak illumination. The photosensitivity of the films is also determined and its variation with temperature is studied.

Polypyrrole films prepared electrochemically using toluene sulphonate as the dopant exhibit molecular anisotropy on a global scale in that the planes of the pyrrole rings are preferentially aligned parallel to the electrode surface. Electrical conductivity measurements on such highly anisotropic films of polypyrrole/toluene sulphonate films are reported. These show that, although there is substantial molecular anisotropy, there is no significant anisotropy of the electrical conductivity of such films. Possible structural models to account for this difference are discussed.

The authors report systematic measurements of the Seebeck coefficient and the electrical conductivity of solid and liquid Mg-Sb, and evaluate the potential of these alloys for thermoelectric power generation. While estimated device efficiencies for the alloys studied do not exceed about 2%, comparison of the properties of these alloys with the commercially successful alloy Pb-Te, as well as analysis of their data, provide some promise for improved device design.

A room temperature long-wavelength 10.6 mu m avalanche-type detector using laser-induced hot carriers is proposed for improvement of the minimum detectable power. The detectors are made by constructing high-low (H-L) junctions on p-type Ge. The L region is a substrate layer and the H region is a layer which absorbs 10.6 mu m radiation, and its also acts as a hot carrier emitter. This junction is referred to as the L-H junction. A responsivity of 41 V W^-1 was obtained at wavelength 10.6 mu m under avalanche voltage conditions. This is comparable with the responsivity of CMT detectors operated at room temperature.

Preliminary electrical characterization of Langmuir-Blodgett films formed from the didodecyldimethylammonium salt of Pt(DMIT)₂ is reported. The in-plane conductivity of the films was found to be strongly voltage dependent for lateral electric fields in excess of about 10 kV m^-1. In the ohmic low-field region of the characteristic the film conductivity was approximately 3*10^-6 S m^-1. Under vacuum, film conductivity decreased so much that the contribution of the film to the total current flow could not be distinguished from the parallel contribution through the glass substrate. This suggests strongly that atmospheric moisture and/or oxygen are implicated in the conduction mechanism of the undoped film. Exposure to bromine vapour led to an increase of about six orders of magnitude in the in-plane conductivity. However, when the bromine was replaced by air the conductivity quickly decreased to about 0.08 S m^-1. Cycling the film temperature between 284 and 300 K gave rise to an unusual observation; the current decreased by several orders of magnitude as the temperature increased. The authors believe this to be associated with changes in film structure. The higher film conductance observed after bromine oxidation was completely lost when films were placed in vacuum, suggesting complete removal of bromine from the samples. The transverse conductivity of undoped films was between two and four orders of magnitude smaller than the in-plane conductance and depended on the type of electrodes used, namely gold, ITO glass or aluminium. Transverse measurements on bromine-doped films were deemed impractical because vacuum evaporation of the counter-electrode would have caused loss of bromine from the films.

An analytic calculation of the initial complex permeability frequency spectra of thin soft ferromagnetic films with in-plane anisotropy, using Landau-Lifshitz theory, is presented. The influence of the thin films' intrinsic parameters, such as saturation magnetization and anisotropy field, on spectra is discussed. A broad band method is applied to determine the permeability spectra of Co-Zr and Co-Zr-Re thin films, in the 0.3 MHz to 3 GHz frequency range. Theoretical and experimental results are compared. The influences of the anisotropy field and the anisotropy dispersion are analysed.

The combination of macroscopic magnetic measurements and micromagnetic observations of domain structure by Lorentz electron microscopy provides a powerful means of studying the behaviour of magnetic thin films. Here two different Co/Pt films have been studied. The same specimens were subjected to similar magnetic field cycles in an alternating gradient force magnetometer (AGFM) and then in situ in the electron microscope. Differences in the scale of the domain structures and the strength of domain wall pinning provided an explanation for the widely differing forms of the hysteresis loops and remanence curves for the two films. The remanence curves define the irreversible changes in magnetization and hence we are able to relate directly the microstructure and the hysteresis properties.

An extended Maxwell Garnett (EMG) model for particulate chiral-in-chiral composites is developed. Volume integral equations and two computationally tractable algorithms for scattering by a chiral inclusion embedded in a chiral host are obtained. These equations are then used to develop the EMG model. Analytic expressions are obtained for the effective-medium parameters in the case of spherical inclusions. Three reductions of the chiral-in-chiral composite are also given.

The steady-state photoluminescence (PL) of mixed AgCl-AgBr crystals was studied. Absorption and emission spectra as well as excitation spectra and temperature-dependences of the main emission bands were measured. For comparison, the same properties of nominally pure AgCl and AgBr were investigated. A 515 nm emission band in the mixed AgCl_0.45Br_0.55 crystals is apparently identical to the emission band of pure AgCl crystals at the same wavelength and is attributed to an intrinsic self-trapped-exciton (STE) recombination process. This assumption is supported by the measured temperature-dependence and excitation spectrum of this band in both crystals. The 515 nm emission becomes dominant in PL of the mixed AgCl_0.45Br_0.55 crystal only after annealing in N₂ atmosphere to 300 degrees C, while PL of pristine mixed crystals is dominated by a 565 nm emission band, attributed to iodide impurity ions, which are apparently present even in the highly pure starting material. This is supported by PL measurements of samples annealed in an I₂ atmosphere. The results also indicate that the nominally pure AgBr crystals contain iodide ion impurities. Thermal treatment of the mixed AgCl-AgBr crystal in a Br₂ atmosphere did not influence the PL bands at 515 and 565 nm, but caused strong increase in intensity of a 750 nm emission band. This 750 nm band also appeared in nominally pure AgBr crystals, and might be due to bromine interstitials.

Monte Carlo simulation is applied to quantitative analysis of thin binary films, one of the constituent elements of which is contained in a substrate. The simulation is based on both the Mott cross section and the energy loss law of Bethe. The k ratios from the samples are measured at various incident electron energies. Monte Carlo analysis was done, based on the measured k ratios. At low energies, the composition of the film is found with a regular ZAF method because the sample seems to be suitable to be considered as a bulk material. At high energies, the composition and thickness of the film are obtained with the above simulation program. When the mean ionization potentials of Duncumb and Reed (1968) are used in the simulation, the concentrations obtained at low and high energies agree well with each other. The choice of ionization cross sections is also discussed in terms of use of the Bethe-type formula.

A gallium liquid metal ion source and an ion energy analysis system were constructed in order to study the ion ejection mechanism. The authors have performed measurements of the energy distribution of ⁶⁹Ga⁺ at elevated source temperatures up to 500 degrees C at a fixed ion current of 2 mu A using a 127 degrees electrostatic energy analyser. Results on the emitted ion energy distribution indicate that a notable secondary peak and a low energy tail are formed in addition to the main peak at source temperatures above 300 degrees C. The field evaporation, field ionization and charge transfer collision are discussed in detail as the ionization mechanisms of the emitted ion. The experimental evidence is presented for the field ionization process as one of the formation mechanisms of ⁶⁹Ga⁺. A comparison between the experimental and theoretical distributions is also carried out.

Details are given of an experimental study of field emission characteristics of diamond-coated Mo electrodes: in particular, a transparent anode imaging technique was used to monitor the spatial distribution of the individual emission centres. This study has revealed the important fact that substantial emission can be obtained at fields as low as 5 MV m^-1. In order to investigate the physical nature of the emission process, a comparative study has been made of emission obtained from a diamond-coated electrode and a bulk carbon graphite electrode. Significantly, it was found that both the graphite-rich diamond film and the diamond-rich graphite electrode shared a similar high-emissivity characteristic, with a high surface density of emission sites. It has also been noted that CVD diamond films have two important properties that are favourable to low-field cold electron emission, namely their negative electron affinity and the presence of graphite inclusions.

VHF glow discharges are employed for high-rate a-Si:H deposition, maintaining good optoelectronic properties. A more efficient radical generation, either due to higher electron densities or an enhanced high-energy electron tail, is generally assumed as the mechanism. A VHF a-Si:H depositing plasma was investigated between 40 and 250 MHz by optical emission spectroscopy, mass spectroscopy, ion energy measurements and electrical impedance analysis. The present study shows that the increase of deposition rate with frequency is essentially due to enhanced ion flux to the growth surface, such that models of deposition kinetics taking into account only neutral species and neglecting the role of ions impinging on the substrate can therefore not be applied to VHF plasma deposition.

CuIn_0.75Ga_0.25Se₂ (CIGS), a promising material for solar cell applications, was produced in the form of thin films by the evaporation of pre-reacted polycrystalline CIGS material onto glass substrates. The deposits were characterized using X-ray diffraction (XRD) and scanning electron microscope (SEM) techniques. They were found to have a strong preferred orientation with the (112) plane parallel to the substrate. Results from energy dispersive analysis with X-ray (EDAX) and Rutherford backscattering spectroscopy (RBS) indicated that the as-grown films were slightly deficient in selenium, otherwise the composition was comparable with the starting polycrystalline material. Electrical measurements revealed both n- and p-type conductivities with surface resistivity values in the range of 10^-1-10³ Omega cm. A two-stage post-deposition heat treatment of the films was performed to improve the composition and crystal structure and to optimize the electrical properties. It was observed that the first annealing stage produced an excellent improvement in the composition of the films. An increase in the film grain size (to >2 mu m) was observed when the films were subsequently annealed in a 9:1 mixture of N₂:H₂. Structural and compositional characteristics are used to explain observed changes in electrical properties.

Thin films of BN were deposited using an electron beam for evaporating boron and a hot filament for activating N₂. The IR spectrum of the deposited film on Si substrates showed a strong absorption at 1097 cm^-1 clearly indicating a cubic structure. Scanning electron micrograph and X-ray diffraction patterns confirm the polycrystalline nature of the films. Raman spectra of the films showed peaks at 1056 and 1304 cm^-1, which are the characteristic Raman lines for cubic boron nitride.

The long-term stability of the electrical power factor of high-temperature annealed n-type SiGe/GaP alloys was investigated under device 'hot side' operating temperatures. Experimental results indicate that the electrical conductivity decreases continuously with time while the Seebeck coefficient increases continuously with time when the alloys are subjected to intermediate temperature heat treatment (973 K). However, when the samples are heat-treated at increasingly higher temperatures, the electrical conductivity passes through a minimum and then increases while the Seebeck coefficient reaches a maximum and then decreases. The results are explained in terms of dopant precipitation and changes in carrier scattering mechanisms. Preliminary results suggest that the enhanced electrical power factor, which accompanies high-temperature annealing, decreases with time when the samples investigated were subjected to temperatures between about 1073 and 1273 K.

There are three kinds of skin depth, based on equality of power loss, current and magnetic flux. For homogeneous media they were hitherto known. For media whose conductivity or permeability are linear with respect to a coordinate, the expression for the first kind of skin depth has been previously obtained by the author. In this rapid communication one may see the difference between the skin depth based on equality of current and that based on magnetic flux equality for inhomogeneous media. However, for homogeneous media, there is no difference between these two measurements.

A new contactless device internal test technique is introduced based on a scanning force microscope enabling dynamic voltage contrast within passivated integrated circuits. A spatial resolution below 500 nm and voltage resolution down to voltages of 0.2 V amplitude are achieved. For the first time static voltage contrast obtained with the scanning force microscope is shown on passivated integrated circuits. Potential and limits of this test technique are discussed.

The experimental evidence of a reduction in the post-implantation damage by a factor of 2 and 1.5 in, respectively, Hg_0.8Cd_0.2Te and InSb caused by magnetic fields of H=0.7 kOe and 2 kOe at T=300 K is reported. This effect follows from the kinetic theory of atomic rate processes in solids linking them with the local electron transport in the submicrometre vicinity of the atoms, overcoming energy barriers. The magnetic field, which decreases the local electron transport, reduces exponentially rates of formation, migration and agglomeration of point defects and this decreases the post-implantation damage.

The intermetallic compounds R₂Al₁₇ (R=Ho,Er) crystallize in the Th₂Zn₁₇-type structure (space group R3m) with the lattice parameters a=8.5064 AA, c=13.0642 AA and a=8.4571 AA, c=13.0027 AA respectively (hexagonal cell). The refinements are based on the space group R3m and converge at the conventional R values: 4.8% for Ho₂Al₁₇ and 5.4% for Er₂Al₁₇. The magnetic susceptibility measurements show a paramagnetic behaviour for these compounds. The magnetic susceptibility obeys the Curie-Weiss law modified by a constant term chi ₀. All contributions in chi ₀( chi _p, chi _orb, chi _VV, chi _L, chi _dia) were calculated. The effective magnetic moments per formula unit are very close to the calculated values.

A new non-destructive method is presented to determine the depth-dependence of the stress tensor sigma _ij from measurements that apply radiations from different conventional X-ray tubes. Experimentally, the method is based on the measurement procedure for the two-dimensional stress state. A suitable parameterization of the three-dimensional state developed from elasticity theory is used to fit all diffraction peak positions simultaneously, which yields the tensor components sigma _ij(z) consistently. The relationship of the new method to more conventional stress determination techniques is briefly discussed. The method has been applied to a test piece formed from a commercial titanium alloy.