The physical, electrical, and temperature dependent properties of thick film polymeric materials are presented. It has been shown that the sensitivity of the planar polymer piezoresistive gauges is comparable to that of the metal-foil gauges. Whereas the sandwich (MRM-metal resistor metal) configurations exhibit similar characteristics to those of cermet thick film MRM gauges, The electrical tests were carried out on films in the MRM configuration and have shown the existence of electroforming at voltages exceeding the forming voltage. Further increasing the applied voltage is shown to produce both s-type and N-type negative resistance within the films, depending on the region of operation within the V- I characteristic.

Unbalanced electromagnetron operated in Ar/n-hexane mixture was employed for deposition of composite Ag/C:H films. For comparison composite Ni/C:H films were prepared in a similar way using unbalanced planar magnetron with permanent magnets. Optical transmission measurements, TEM micrographs, and dc electrical measurements, were used to study ageing effects of the composites in the ambient atmosphere.

Fractal structures have been observed in discontinuous Mn films evaporated onto quartz-glass substrates in vacuo (10^-8 Torr). The microstructures of the films were examined with high resolution electron microscope. On the basis of the micrographs, the coverage coefficients were determined for the Mn films. The fractal dimensions of Mn films were determined using the box-counting by squares method. It has been found that the fractal dimensions D depends on the film structure characterized by coverage coefficient p. In the considered coverage coefficient range the fractal dimension increases with increasing p, approaching D equals 2 for continuous films.

Mn discontinuous films with different thicknesses d were evaporated onto quartz-glass substrates at different temperatures under vacuum conditions (p equals 10^-8 Torr). The microstructures and crystallographic orientations were examined with high resolution electron microscope. On the basis of the diffraction patterns the contents of islands and their influence on the electrical properties were determined. The temperature dependencies of resistance R(T) were measured in vacuo in situ for the Mn films with different thicknesses. Making use of the measured data the activation energies of resistance E were calculated for the films with different thicknesses and for the films obtained under different evaporation conditions.

This paper shows wide application range of composites consisting of conductive organic and/or inorganic filler and polymer insulative matrix. An original low- and high-temperature polymer thick film conductive and resistive compositions, elaborated at the Technical University of Wroclaw, are described in more detail. Examples of devices fabricated with their usage are presented.

For the purpose of this review, thin films in electronics are regarded as having thicknesses of up to 5 micrometer. Although films thicker than this can be made and used, the step to thick film technology which involves pastes, screen printing and plasma deposition techniques, is a substantial one where the considerations are primarily technological. Thin films range typically from a few nanometers in thickness as applied in quantum well structures and deposited as thin semiconductor layers using molecular beam epitaxy, to thicker dielectric films up to 1 micrometer thick or even thicker and which are generally deposited by thermal or electron beam evaporation or by a sputtering process. In between we have metal and alloy films used as contacts or conducting overlays in microelectronics as well as semiconductor and insulator thin films used in a wide range of active devices such as transistors, diodes, photocells and electroluminescent layers, and in a variety of sensors. In this connection gas sensing including the use of devices which are sensitive to chosen gases such as sulphur dioxide or toluene vapor for example, can be achieved using specially prepared layers of novel phthalocyanines consisting of a few monolayers deposited by Langmuir-Blodgett technique. From consideration of thin film research strands of recent years some suggestions of the probable developments of thin film assemblies in electronics are made.

When a thin gold film is electroformed under an oil diffusion-pumped vacuum, the device subsequently displays a voltage controlled negative differential resistance (NDR) with electroluminescence (EL) and electron emission (EE). In this work we present experimental data, showing a device continuing to exhibit NDR when taken from vacuum to atmospheric pressure in either argon or nitrogen gas. NDR is observed over many voltage cycles with an accompanying EL, which is in contrast to the suppression of NDR which occurs on the first cycle for a deice in air at atmospheric pressure; NDR can only then be re-established by returning the device to vacuum. Therefore, as NDR can be achieved at atmospheric pressure in argon or nitrogen gas this indicates it is the presence of oxygen that inhibits the NDR conduction mechanism when a voltage is applied at atmospheric pressure.

The initial stages of growth of thin metal films in both two-dimensions (discontinuous metal films on dielectric substrates) and three-dimensions (plasmachemically prepared composite films with metal islands located in the dielectric matrix) are studied by the combination of direct measurement and modeling. For the analysis of film photographs from transmission electron microscope and for the description of spatial distribution of objects the methods of mathematical morphology were used, the special attention being devoted to the covariance method. The interpretation of the derived characteristics and the extension of the analysis for composite films was performed by the computer experiment, while simulated micrographs with known distribution of objects were processed by the same morphological algorithms as experimental data.

The ac electrical properties of evaporated cadmium telluride thin films sandwiched between ohmic aluminum electrodes have been investigated for temperatures of approximately 200 - 400 K over the frequency range 10² - 2 multiplied by 10⁴ Hz. The ac conductivity (sigma) ((omega) ) was found to follow a (sigma) ((omega) ) varies direct as (omega) ^N law, where (omega) is the angular frequency and the exponent s systematically decreases with increasing temperature from a maximum value close to unity at approximately 200 K. This low temperature value is consistent with values of s expected from the model of Elliott for correlated barrier hopping, and other features predicted by the model, such as the increase in (sigma) with temperature and the strong frequency dependence at low temperatures, were also observed. Measurements of (sigma) as a function of temperature for various fixed frequencies showed that in the higher temperature range the conductivity activation energy was typically 0.66 eV depending on the frequency, whereas at low temperatures its value was of the order of 0.01 eV. These values are indicative of a free-band conduction process at higher temperatures and confirm the existence of hopping conduction at lower temperatures. In the hopping region the density of localized states was estimated to be approximately 9.9 multiplied by 10²² m^-3, and was of a similar order to the trap concentration determined previously from dc space-charge-limited conductivity measurements. Measurements of capacitance C as a function of frequency and temperature showed a decrease in C with increasing frequency tending towards a constant value for all temperatures. C also increased with increasing temperature, with the most significant increase occurring at low frequencies. This type of behavior is consistent with an existing equivalent circuit model which assumes the existence of ohmic contacts to the films and a thermally activated conduction process.

The transformation of high-resistivity amorphous Bi_1.68Pb_0.32Ca_1.85Sr_1.75Cu_2.85O_y to superconductive material has been characterized by structural, thermochemical, transport and SEM measurements. X-ray powder diffraction confirmed that rapid solidification of Bi-Pb-Ca-Sr-Cu-O_y yields amorphous material. In further heat treatments the sequential crystallization of 2201, 2212, 2223 phases have been identified. The differential scanning calorimetry indicated an exothermic crystallization peak at 520 degrees Celsius with corresponding enthalpy of 62 J/g. SEM studies revealed that the grain size increases with sintering time and formation mechanism in the interior of the bulk is different from that at the edges of the superconducting glass ceramic rods. Thermal cycling of the insulating glass to a temperature above that required for crystallization results in a transformation from an insulating to a superconducting material with a T_c (R equals 0) of 105 K. It is also shown that the glass ceramic rods obtained by re-heating glass rods at 850 degrees Celsius for 120 hours have a T_c (R equals 0) of 105 K while the disk specimens obtained by re-heating the powdered glass compacts in the same way do not exhibit superconductivity above 85 K. This difference in superconductivity between the specimens is discussed in terms of the crystallization process and the amount of oxygen absorption of the specimens during heating.

Thermochromic switching between a low-temperature and high-temperature less transparent state is possible in thin films based on vanadium dioxide (VO₂). The critical temperature T_c at which the transition takes place in VO₂ is on the order of 68 degrees Celsius which can be depressed towards a comfortable temperature by several techniques, including dopants. Dopants can be inserted by electrochemical means. This work is an exploratory study of the electrochromism of Li_xVO₂ with a view to 'smart window' applications. Thin films of Li_xVO₂ (0 less than or equal to x less than or equal to 0.43) were made by reactive sputtering and annealing electrolyte of LiClO₄ and propylene carbonate. A maximum lithium content of x equals 0.43 was accomplished. Optical spectral response at wavelength pertinent to solar radiation was reported. Lithium insertion increased the transmittance gradually and reversibly i.e. Li_xVO₂ showed electrochromism and bleached under Li insertion. Li_xVO₂ also showed thermochroism, although to a smaller degree than VO₂ and was most transparent at low temperature. Temperature- dependent electrical conductivity and thermoelectric power measurements were also performed. A conductivity transition by approximately 3 orders of magnitude was seen at approximately 60 degrees Celsius in VO₂. This transition decreased in proportion with the amount of Li intercalation and was less than one order of magnitude in Li_0.43VO₂. Lithiation also decreased T_c by a few degrees Celsius. The thermoelectric power showed a well defined increase when T_c was exceeded.

The process of electronic conduction in granular metals in the dielectric regime is being considered. The charging energy model of conduction in granular metals recently proposed in the literature, is extended to include the effect of the clustering of metallic component which takes place when metal-insulator transition is approached. The electrical conduction is modeled by a resistor lattice built from conductances, G_ij equals G₀exp(-2_chis_ij-E_ijlkT), where (chi) is the decay rate of the electron wave function in the insulator, k is Boltzmann's constant and s_ij and E_ij are intergrain separation and intergrain charging energy respectively. The process of clustering of metallic component is introduced as highly conductive bonds which appear in the lattice with average number of B bonds per lattice site. The critical path method is used to find the conductivity, (sigma) , of the model. Temperature dependence of, (sigma) approximately equals exp[-(T₁/T)^1/2] in agreement with widely observed experiments is found. The temperature, T₁, is found to decrease with B increasing i.e. when metal-insulator transition is approached in agreement with experiments reported for real granular metals. Numerical simulations of the model are performed. Quite good agreement between the critical path analysis and numerical data is found.

This paper has three objectives. For those who have no prior knowledge of discontinuous thin metal film research, it serves to introduce the basic concepts of electrical conduction in such structures, i.e., electron tunneling between discrete metal islands, with an associated activation energy of electrostatic origin. In addition, some of the properties and potential applications which continue to drive research in the field are summarized. For those with greater familiarity with the field, the objective is to argue for the concept of contact injection of charge carriers as a fundamental basis of the conduction mechanism. The argument is based on the observation of asymmetric electrode effects with both ac and dc properties. The primary difficulty in both research and application of such films lies with drift and lack of reproducibility, problems which may now be resolved by use of the scanning tunneling microscope (STM) or atomic force microscope (AFM) for structural control.

Electrophoretic deposition from non aqueous emulsion is one of the useful methods for forming polymer thin films selectively on metal electrodes. It has a potential to be used for forming an interdigital electrode for multilayer capacitor or actuator. A heat resistant polymer, polyimide (PI), film was prepared by the electrophoretic deposition method. Conductivity and dielectric strength were measured, comparing with casting and conventional PI films.

An oxidation of aluminum films in oxygen plasma of dc glow discharge is studied by computer experiment. The necessary data is derived from direct measurements. The complete model consists of three parts -- the modeled source of the oxygen plasma, the model of the transport of charged particles through the sheath between undisturbed plasma and substrate and, finally, the description of physical processes occurring during oxide formation on the solid surface. The description of volume interactions which takes part in the undisturbed plasma was based on a macroscopic kinetic approach with 12 kinds of charged or excited particles. As a result of the first part of the model the steady-state concentrations of all kinds of particles were derived. These results are used as input data for the second part of the model, which is the main task of the present paper. The physical processes which take part in the interaction of plasma- aluminum substrate were analyzed by the iterative hybrid method -- a combination of molecular dynamics and Monte Carlo approaches. This method was employed to study the transport of charge in the self-consistent electric field under the influence of interactions with neutral species in the sheath. Both the plasma oxidation and plasma anodization were modeled and the effects of varying bulk plasma and sheath parameters on the ion and electron distributions at aluminum surface were examined. These particles can be used in the third part of the complete model to analyze the growth of alumina film.

The lateral resistivity of evaporated CdSe thin films has been measured using the van der Pauw technique. Measurements were performed as a function of the film thickness, the deposition rate and the substrate temperature during deposition. Such measurements are useful in the context of the development of inexpensive solar cells based on this material. In contrast to some other cadmium compounds the mean resistivity appeared to increase with increasing thickness, prior to a rapid decrease at a thickness above about 1 micrometer. This effect is thought to be related to the varying composition of the evaporating CdSe charge during the course of the evaporation process. Films deposited at a substrate temperature of 200 degrees Celsius (473 K) showed a rapid increase in resistivity from below 10² (Omega) m to above 1 (Omega) m as the deposition rate increased up to approximately 0.5 nm s^-1, while for rates above this value and up to 3 nm s^-1 the resistivity remained essentially constant. This behavior is thought to be related to a decrease in mobility and/or free carrier concentration resulting respectively from increasing grain boundary scattering and trapping effects, as a result of a decrease in the mean grain size with increasing deposition rate. Resistivity was strongly dependent on the substrate temperature during deposition, showing a moderate increase with increasing temperature up to about 75 degrees Celsius (approximately equal to 350 K), followed by a very rapid increase of typically three decades up to 100 degrees Celsius (373 K), above which the value stabilized at an essentially constant value. Previous work has identified the origin of lower resistivity CdSe films as being the result of an excess of Cd ions while stoichiometric films are normally of higher resistivity. The present results indicate that a substrate temperature in excess of 100 degrees Celsius (approximately equal to 400 K) is necessary for the deposition of stoichiometric films. As expected conductivity was thermally activated and the resistivity decreased with increasing temperature. Samples prepared at a substrate temperature of 200 degrees Celsius (473 K) showed activation energies of approximately 0.02 eV and 0.14 eV at lower and higher temperatures, respectively. The low temperature behavior is consistent with conduction via a hopping mechanism, while the latter is appropriate for thermal excitation over inter-crystalline potential barriers as proposed by Petritz and previously observed in CdS films.

Sandwich MIM structures Al/Al₂O₃/Au were measured before and after electroforming. I-V characteristics and noise of leakage and emission currents were measured in vacuum at various temperatures. Calculated power spectra of current noise of white, Lorentzian and 1/f^a type reflect relaxation processes and dominating conduction mechanisms at various applied voltages.

Dc conductivity and Hall effect measurements were performed on Cu-GeO₂ thin films with the aim of obtaining information about dc conduction mechanism. The conductivity results reveal that the activation energy is temperature dependent, increasing significantly above a btransition temperature T_t. Hall mobility showed a sign reversal around T_t, above which it increased with increasing temperature reaching a maximum at a critical temperature T_c. Above T_t, the conductivity is best described by small polaron hopping model. Below T_t, the Hall mobility shows a significant rise with decreasing temperature, indicating polaronic band conduction mechanism. Various parameters associated with polaronic formation are calculated.

An analytical description of temperature dependence of resistance in a classical percolation system is presented for the first time. Three concentration ranges of conductive phase -- below and above percolation threshold as well as inside smearing region -- have been analyzed. Useability of presented results has been discussed for such random inhomogeneous media as cermet and polymer thick film resistors as well as cermet thin film ones.

Numerical simulations of 1/f noise in random networks in which bonds take resistances r approximately equals exp(-(lambda) x), where x is a random variable and (lambda) >> 1, are presented. For microscopic noise generating mechanism which obeys the form of {(delta) r(delta) r} approximately equals r^{2 $plus (theta} ) it is shown that the effective noise intensity C equivalent S(Omega) , where S is the relative power spectral density of the fluctuations (delta) R of the resistance R of the network and (Omega) is the networks volume, is given by C approximately equals (lambda) ^mexp(- (lambda) (theta) x_c) where X_c is related to percolation threshold. Numerical simulations performed for (theta) equals 1 and (theta) equals 0 give m equals 2.3 and show that exponent m is 'double universal' i.e., it is independent of the geometry of the lattice and of microscopic noise generating mechanism.

The compound CuMnFeO₄ was crystallized with cubic structure. Transport properties indicate that the compound is a p-type semiconductor. Magnetic properties indicate that the compound is ferrimagnetic and Mossbauer investigations indicate that Fe³⁺ ion is present at A as well as at B sites. The probable ionic configuration of the compound is Fe_0.8³⁺Cu_0.2²⁺[Fe_0.2³⁺Cu_0.8²⁺Mn_0.8³⁺Mn_0.2⁴⁺]O₄^2-.

A formula for the band structure energy U_bs of simple liquid metals in the terms of the interference function a(q) is derived. U_bs is evaluated both for experimental and theoretical shape of a(q). Although the contribution of U_bs to the total energy is small, it is suggested that presented formalism could be used for other atomic properties, where its role is expected to be more pronounced.

An empirical form of screened model pseudopotential, proposed by Veljkovic and Slavic, is exploited for the calculation of resistivity of seven liquid metals through the correct re- determination of its parameters. The model derives qualitative support from the close agreement obtained between the computed results and the experiment.

The GaAs(001) surfaces were submitted to 10 - 100 keV oxygen ion bombardment at room temperature and then they were thermally annealed in order to restore the initial topography. The present paper is motivated by a desire to correlate the electronic properties of GaAs crystal to its structure. It is the main purpose of this work to investigate the nature of damage conducted by the implanted oxygen ion and to show the changes in the structure of GaAS(001) surface resulting from surface disorder due to ion implantation.

Voltage contrast technique is very useful for semiconductor devices characterization but standard SEMs are not equipped with proper facilities. A simple voltage contrast detection unit based on an original design of the electron energy analyzer has been presented. The detachable unit enables us to display and measure the potential distribution on the surface of integrated circuit.

In the paper the analog and digital methods of TOPO mode realization in a scanning electron microscope (SEM) by means of backscattered electron signal (BSE) have been presented. The detector system consists of four BSE detectors, their biases, and the same number of current sensitive preamplifiers placed inside the vacuum chamber. Two pairs of opposing semiconductor diodes of a small surface placed mutually perpendicularly have been used. BSE signals enter low pass filters and the next amplification stages in the signal conditioning circuit in order to prepare them for further processing.

In this work experimental technique for determination of energy distribution of localized states of charge carries in high-resistance semiconductors as well as its mathematical description have been developed. This method has been applied for determination of energy distribution of electrons and holes in an a-Se layer at the temperature of 170 and 145 K in the energy interval 0.59 - 1.8 eV relative to the conduction edge of the carrier mobility gap. It has been discovered that light with lambda less than 1.06 micrometer generates not only holes, but electrons, too. Peculiarities of electron localization states in an a-Si:H layer at 85 K have been investigated.

Digital PITS technique was applied to study deep-level defects in semi-insulating GaAs and InP. The studies were completed by measurements of ESR spectra on the same wafers.

Electrically active defects in preannealed n-type Cz-Si crystals subjected to high-pressure heat treatment were studied by deep level transient spectroscopy (DLTS). Experimental evidence is given that electron traps at E_c - 0.20 eV, E_c - 0.45 eV and E_c - 0.62 eV are presumably related to an oxygen-multivacancy complex, an acceptor level of Ni and a point defect decorating extended defects, respectively.

Photoreflectance spectroscopy as the nondestructive, contactless, room temperature method to investigate semiconductor layers, interfaces, structures and devices is presented. Principles of the method are described. Application to the investigations of the III-V compounds structures, including heterojunction bipolar transistors, high electron mobility transistors vertical cavity surface emitting lasers and quantum dots arrays are shown.

The LBIC method was used to investigate the trapping-recombination centers in GaAs:Si layers grown by MOCVD method. The special test structure was developed and performed. The model which joins the measured signal changes with the presence of trapping centers from substrate (EL2 deep levels) and surface.

In the present paper we have shown the results of our DLTS studies in GaAs_0.945Sb_0.055 LPE semiconducting compound. Only one electron trap has been detected within whole experimental temperature range 80 K - 300 K. The concentration of the trap was found to be of the order of 10¹² cm^-3within the whole barrier region of the junction. The trap behaves very different from the usually observed traps in DLTS experiment. The DLTS peak is asymmetrically broadened and shifts to lower temperatures with increasing width of filling pulse which implies that dislocations are the origin of the trap.

III-V mixed crystals are interesting for their application in modern optoelectronics and microwave electronics. Two mixed systems, namely GaAs_1-xSb_x and GaAs_{1-x- y}Sb_xP_y, were chosen to investigate an influence of gallium phosphite and gallium antimonide added to gallium arsenide on band structure properties and crystal lattice structure.

The influence of metallic contaminants (Ni, Mo) on the oxygen precipitation process during high temperature (HT) treatment under hydrostatic pressure (HP) was studied. No significant influence of Ni and Mo contaminants on the oxygen precipitation process at 1400 K was observed. Changes of interstitial oxygen concentrations c₀ after HP-HT treatment for contaminated and for non-contaminated samples were less than 10%. The metallic contaminants (ni, Mo) cause mostly generation of large strain fields in the matrix probably related to metallic precipitates as evidenced by x-ray topography.

The GaAs layers of a thickness of 200 nm and donor concentration of about 10¹⁸ cm^-3 were bombarded by 0⁺ ions with doses above 10¹³ cm^-2 at the energies of 125, 150, and 250 keV. The dc and ac conductivities of GaAs layers at the temperatures of 77 - 330 K were investigated. The dc measurements of the resistivity as at function of temperature indicate the following relationship: ln(rho) approximately equals T^-1/4. It confirms the variable-range of hopping conductivity. The ac conductivity measurements of GaAs layers in the frequency range of 15 Hz - 30 kHz show the dependence of an activation energy on trap emissivity according to the formulae e approximately equals exp(-E_a/kT). The values of an activation energy calculated from the slope of Arhenius line is of 75.06 meV.

Galvanomagnetic measurements were performed on the square shaped samples after Van der Pauw and on the Hall bar at low electric fields app. 1.5 V/cm and magnetic induction app. 6 kG in order to make a comparison between the theoretical and experimental results of the temperature dependence of mobility and resistivity from 70 K to 300 K. A calculation method was obtained of the drift mobility and the Hall mobility in which the scatterings are applied: on ionized impurities, on polar optical phonons, on acoustic phonons (deformation potential), on acoustic phonons (piezoelectric potential) and on dislocations. The elaborated method transformed to a computer program allows us to fit experimental values of the resistivity and the Hall mobility to those calculated. The fitting procedure makes it possible to characterize the quality of the n-type GaAs MBE layer, i.e. the net electron concentration, whole ionized impurities concentration and dislocation density after Read space charge cylinders model. The calculations together with the measurements allow us to obtain compensation ratio value in the layer, too. The influence of the epitaxial layer thickness on layers measurements accuracy in the case of Van der Pauw square probe was investigated. It was stated that in the layers under 3 micrometer the bulk properties are strongly influenced by both surfaces. The results of measurements of the same layer using the Van der Pauw and the Hall bar structure were compared. It was stated that the Hall bar structure only could be used to obtain proper measurements results.

Mesoscopic phenomena in nanostructures that incorporate semimagnetic semiconductors (diluted magnetic semiconductors) may exhibit a number of novel features driven by the s-d spin-exchange interaction. The influence of this interaction upon quantum interference effects, such as universal conductance fluctuations, low-frequency noise and quantum localization, is described. Results of recent millikelvin magnetoconductivity measurements, carried out for microstructures of Hg_1-x-yCd_yMn_xTe bicrystals and for submicron wires of MBE grown Cd_1-xMn_xTe:In epilayers, are presented. Particular attention is paid to a new driving mechanism of the magnetoconductance fluctuations -- the redistribution of the electrons between energy levels of the system, induced by the giant s-d exchange spin- splitting.

The advantages of introduction of magnetic ions in semiconductor quantum structures are discussed and illustrated by relevant examples from recent research results, such as growth of spin superlattices and studies of resonant tunneling in double quantum well structures. Particular attention is paid to non-conventional methods of characterization of interfaces made possible by the presence of magnetic ions: spin tracing, useful for determination of the interface composition profile width, and detection of undulation of the quantum well surface by temperature dependent polarization measurements of the Mn ESR Raman cascade.

By using the advantage of reactive rf magnetron sputtering technique the films and multilayers of compositions Bi₂Sr₂CaCu₂O_x/Bi₂Sr₂CuO_y were successively grown. The angular dependences of the critical current j_c in magnetic fields up to 20 T of multilayers with ultrathin layers are studied at different temperatures. The j_c anisotropy of the multilayers is compared to that of single phase films. In addition, the influence of the heavy-ion radiation on Bi₂Sr₂CaCu₂O_x epitaxial films is studied.

A model of controlled-barrier quantum dot based on GaAs/AlGaAs heterostructure has been considered. The analytic form of potential V(x,y) confining the 2DEG has been assumed. It results from application of two biasing voltages: bottom gate U_g and upper electrode U_b. Schrodinger equation for the model has been solved and on this basis transmission coefficient (T) vs electron energy has been calculated for different values of drain to source voltage. Resonance tunneling results in T equals 1 for eigen values of energy within the quantum well. When U_ds increases T decreases below one and shifting of the peaks into the higher energies takes place. Abrupt changes of drain current and peaks in dynamic conductance both versus U_ds have also been found for zero temperature. When temperature increases the smearing of steps in the current and broadening of conductance peaks have been observed.

Charge density wave (CDW) occurs in low-dimensional solids as a consequence of Peierls Transition. Various field and frequency-dependent effects as well as of excess noise are related to CDW transport. Low frequency (in the range of 10 - 10⁶ Hz) dielectric relaxation as well as voltage fluctuations as a result of internal dynamic or sliding CDW in quasi one- dimensional chain compound (TaSe₄)₂J single crystals were investigated. The activation energy for normal conduction obtained from low field resistivity was (Delta) E equals 0.122 plus or minus 0.004 eV. The most useful expression of dielectric relaxation for strong damped system with one degree of freedom is (epsilon) ((omega) )varies direct as(1 plus i(omega) (tau) ₀)^-1degree where relaxation times (tau) are distributed at average (tau) ₀ . (tau) ₀ vs 1/T shows thermal activation (Delta) E equals 0.124 plus or minus 0.004 eV. Voltage fluctuations produced by a sliding CDW are found to originate from random thermally activated transitions between metastable states. Noise power spectra between 500 Hz and 600 kHz at temperatures from 165 to 215 K have S(f)varies direct asf^-a dependence. Distribution of relaxation times and temperature- dependent shortest relaxation time reflect CDW internal dynamics and importance of free carriers on it.

Numerical studies of dimensionless conductance g in 3D metal-insulator systems have been reported. A discrete lattice site quantum site-percolation model has been defined. It consists of two semi-infinite ideal metal electrodes and a disordered sample of size L multiplied by L multiplied by L located between them. Disorder of the sample is controlled by metal fraction p of conducting particles randomly occupying the sites of cubic lattice with probability p. Tight- binding Hamiltonian with diagonal disorder and probability density of site energies of the form P((epsilon) _n) equals p(delta) ((epsilon) _n) plus (1-p)(delta) ((epsilon) _n - (infinity) ) has been considered. Magnetic field has also been introduced to the model. Conductance g has been calculated using Landauer-Buttiker formula and Green's function technique. It has been found that above classical percolation threshold, that is for p greater than p_c approximately equals 0.312, a second critical point exists denoted as p equals p_q. In the region p_c less than p less than p_q, g approximately equals exp(-L/(xi) _loc), where (xi) _loc is localization length, the system is localized while in the range p greater than p_q conductance tends to indicate g approximately equals L metallic type behavior. By fitting the estimated data of (beta) (g) vs 1ng to the approximate relation for the scaling function (beta) valid in the vicinity of the critical point, critical conductance g_c equals 1.32 plus or minus 0.19 and correlation length critical exponent v equals 1.6 plus or minus 0.2 have been estimated. It has been found that in p less than p_q region the system indicates negative magnetoresistance typical for disorder induced localized states phase, while p greater than p_q range, magnetoresistance is positive as expected for extended states phase.

Experimental and theoretical research on magnetoelastic properties of magnetic superlattices is reviewed. The importance of interfaces and the occurrence of surface magnetoelastic effects is emphasized. It is shown that the dependence of effective magnetostriction on the magnetic layer thickness is due to the magnetostrictive strains localized at the interface.

The behavior of the magnetron sputtered Ge films under annealing in vacuum at various temperatures up to 1173 K is described. The relation between the dc conductivity and the thermoelectric power versus temperature (300 - 500 K) for films annealed in various conditions is given. The changes in the electrical parameters of films were correlated with data obtained from structural analysis and the optical measurements.

By means of rf sputtering the ferroelectric thin film of PZT-type with the chemical constitution Pb(Zr_0.52Ti_0.46W_0.01Cd_0.01)O₃, thickness d_f equals (1 - 2.5) multiplied by 10^-6 m and polycrystalline structure was obtained. Either metallic foils or ceramics were used as substrates. In the case of thin film deposition on steel substrate and platinum at low temperatures (T_s less than 723 K) the nonferroelectric intermediate layer with the same chemical constitution but with the pyrochlore type structure has been created. Structural peculiarities are reflected in anomalous dielectric dependencies of the thin films. Obtained results are considered and discussed.

The problem of methane sensor application in the domestic environment is presented. Tin dioxide thick film technology sensor conductance changes depending on methane concentration. Simple calibration cannot be approached because the conductance is also strongly influenced by humidity. Nevertheless, despite changing humidity accurate methane concentration determination is possible using a two-sensor system. It includes methane sensor and very selective humidity sensor. Artificial neural network is used for reasoning about methane concentration based on responses of these sensors. Feedforward type network is simulated, trained with backpropagation method and tested. The network's accuracy is compared with simple calibration of the sensor.

Thick film thermistors based on spinel-type semiconducting oxide (Mn_1.6Co_0.8Ni_0.35Ru_0.25O₄) were studied. On the basis of the structure analysis (SEM observations and x-ray investigations) the computer model of the thermistor was proposed. The model was created in two steps. First, the structure of the element was simulated by generating of the spinel-type particles at the glassy matrix. Next, the model of the real structure was converted to the resistive network consisting of nodes and bonds. Various types of the resistances were considered (crystallite/grain resistance of the oxide, boundary resistance between grains, glassy layer resistance between grains). As a result the effective resistances of the random network at the different temperatures were calculated using the voltage nodes method basing on the first Kirchhoff law. Additionally the ruthenium dioxide powder was considered as a modifier. This paper presents some experimental and theoretical results obtained from the proposed model.

The continuation of work reported earlier on the development of a discontinuous thin palladium film hydrogen sensor confirms the effects first described and interpreted by Barr. The basic principle is that quantum-mechanical tunneling between the discrete metal islands of the film is modulated by barrier height increases due to the surface adsorption of hydrogen, and by gap reduction due to island lattice swelling. Transient thermal effects do not yet permit quantitative verification of the model.

The aim of this work was to construct a simple gas detector capable to detect the gas and its concentration.

Electroconducting polymer films of polyaniline (PANI) are a promising material for molecular electronics and microsensors. The results of investigation of the PANI films conductance with help of I-V curves, temperature and concentration measurements are presented. Polymer films were produced by the deposition from a saturated PANI solution in dimethylformamide onto the gold interdigital contacts, followed by drying in air. The ammonia effect on PANI can be explained in such a way that NH₃ adsorption/desorption directly modulate the PANI level of doping, i.e., the film resistance.

Surface plasmon resonance (SPR) is a technique, which is extremely sensitive for changes of dielectric characteristic of thin biology layers, present on top of metals, which supports SPR. This fact defines increased interest to development of immunosensors, based on this effect. The working characteristics of such sensors are dependent on many factors, both physic peculiarity and stable surface characteristics of the metal layer, which supports plasmon oscillation (silver, gold), is primary. The experiments show that type of treatment of glass substrate can change significant silver properties such as plasmon carrier and define character of absorption activity to protein molecules. Sensitivity of SPR immunosensors for change of adsorption cover thickness dependents of pH and ionic strength of protein solution also of silver surface hydrophilicity or hydrophobicity. In particular, we see a bovine serum albumin (BSA) adsorption maximum for such technology parameters: ion-plasma treatment before silver evaporation on the glass slides, pH equals 5, ion strength 20 mmol, and the surface of the silver must be highly hydrophobic.

On the basis of the thin films of BaTiO₃ and LiNbO₃ the piezoelectric isotropic and anisotropic sensors of dynamical deformation (SDD) have been constructed and investigated. It has been ascertained that the electrical signal of isotropic SDD is proportional to the sum of the main components of the relative deformation tensor of the surface of the sample whereas the anisotropic sensor signal depends on the angle (phi) between the sensor axis and the main axis of the deformation tensor of the sample. The stability of their parameters has been ascertained under repeated deformation of the sample surface and repeated heating/cooling.

Spin-on phosphorus diffusion source has been used for emitter formation in silicon solar cells. It is shown that commercially available phosphorosilicamer emulsion used for that purpose can be easily modified by adding alcohol solution of P₂O₅ thus allowing us to obtain junctions with different dopant profiles for the same process conditions. SIMS curves have been taken for several samples and compared with theoretical simulation of diffusion profile showing that diffusion driven from spin-on source may strongly differ from that carried out from classic POCl₃ source. Results of some experiments on emitter passivation by simple dry oxidation are also presented.

Plasma polymers were deposited on various surfaces using Ar/n-hexane/water working gas mixture. In most cases a test surface consisting from glass substrate coated by plasma polymer of Ar/n-hexane was used. It has been found that wettability of this test surface improves with the increased water concentration in a working gas mixture or with the increased power to the discharge. The increased concentration of polar groups was observed by FTIR absorption in the films stored in humid environment. Rate of the water absorption in dependence on power used for the film deposition is discussed.

Structure and pyroelectrical properties of K-, Na- and Li-stearate films, obtained by vacuum deposition, were studied. IR-spectroscopy, x-ray diffraction, scanning tunneling microcopy and scanning electron microscopy observations show a large difference in the molecular ordering and orientation in these films. The values of the pyroelectric coefficient g also essentially differ for these compounds. The largest value of g is observed for NaSt films and has an order of 10^-6 Coul*m^-2*K^-1.

Optical and electrical characteristics of single- and double-layer organic electroluminescent (EL) diodes based on commonly used low-molecular weight materials of an aromatic diamine (TPD) and 8-hydroxyquinoline aluminum complex (Alq₃) were investigated in order to compare their operation mechanisms.

This work deals with an investigation of the electrical conductivity and the light emission in a system involving gold islands and organic stearon molecules (C₁₇H₃₅)CO. An essential change in the electrical conductivity and the light emission characteristics was found on passing from the constant to the alternating operation mode. The results obtained point out a strong effect of the organic layers present between the gold nanoparticles on I-V characteristics and light emission spectra of the composite systems concerned. The data are interpreted in terms of effects of electric field and Joule heating on the conductive channels formed in the island films.

The electrical properties of chloroindium phthalocyanine (ClInPc) in a Au-ClInPc-metal sandwich structure were measured, both under vacuum (less than 1.3 mPa) and at atmospheric pressure using Au, Sn and Al top contacts. In addition to current-voltage characteristics the electroluminescence (EL) from the devices was measured and, under vacuum, the electron emission (EE). At atmosphere all devices show a non-linear conduction that decays slowly over many hours. Under vacuum the Au-ClInPC-Au devices display a voltage controlled negative differential resistance (NDR) accompanied by a peak in the electroluminescence and high field electron emission. The Au-ClInPc-Sn devices under vacuum show an NDR with a distinct valley but with no detectable electroluminescence or electron emission. The Au- ClInPc-Al devices do not display NDR under vacuum, but show a non-linear conduction approximately 30 times greater than that observed at atmosphere.

Electroluminescence (EL) inorganics is a phenomenon of both fundamental and practical interest. Defined as direct conversion of electricity into light incorporates many physical processes which are not yet fully understood. Considered originally as an organic analogue of the Destriau effect that is high-field or intrinsic EL found previously in inorganic phosphors, remains still obscure since narrow bands in organic solids rule out electron acceleration to energies allowing impact generation of electronic excited states. Therefore, the search for wide-band organic materials is a challenge to design and to fabricate organic intrinsic EL devices. The recombination radiation following the excess charge carrier injection into a luminescent material stands for injection EL. This type of EL is commonly accepted as a basis for the emission of light from organic materials sandwiched between metal electrodes. In this review, some consequences of the band width and energy level positions in low-molecular weight organic materials and polymers are discussed. Fundamental concepts are illustrated using the notions of recombination ((tau) _rec) and transit ((tau) _T) times of charge carriers. Injection-controlled ((tau) _rec greater than (tau) _T) and volume-controlled ((tau) _rec less than (tau) _T) injection EL modes are distinguished in organic light- emitting-diodes (LEDs). Two routes to fabricate spectrally tunable organic LEDs are discussed: (a) building multilayer devices with various materials as chromophores (emitters) and (b) employing single-layer conjugated polymer systems with different main-chain molecular structures and blending luminescent polymers into the host polymer matrix, or molecularly-doped non-conjugated polymers with appropriate selection of the optically active component. Charge carrier trapping and excitonic interactions are important factors affecting the recombination routes and production of emitting states as is demonstrated on EL from single organic crystals. Using photoinjecting contacts instead of dark-injecting electrodes allows us to design a unique light transducer combining an organic EL diode with the photosensitive film. Selected examples of organic LEDs and light transducers are presented. Some directions for further work are given.

The investigation of frequency-temperature dependences of complex dielectric permittivity in 10 - 10⁵ Hz and 240 - 330 K regions has been performed for poly (epoxypropylcarbazole) (PEPCa) layers. The high-frequency relaxation (named as (beta) ) has been revealed beside (alpha) -one. The (beta) -relaxation region possesses the properties characteristic of secondary relaxation. The existence of two relaxation regions is likely to be due to free cooperative reorientational motion in the vicinity of T_g ((alpha) -relaxation), and to the restricted motion of the same dipolar units at lower temperatures ((beta) - relaxation).

(sigma) -conjugated polymers represent a new group of charge-transporting molecular materials. The charge carrier transport is influenced by two factors: delocalized movement inside conjugated domains and intra- and interchain hopping. Polarons play an important role. Electrostatic interactions of polar additives or attached polar side groups with polarons influence the polaron binding energy and the charge hopping.

New copolymer materials based on polyaniline (PANI) were prepared. The electric and dielectric characteristics, i.e., dependences of the impedance and the permittivity on the frequency and temperature are studied.

Absorption spectra of ladder-like forms of polyacrylonitrile were investigated by spectroscopic ellipsometry, transmission and reflectivity measurements. The samples of polyacrylonitrile were deposited by spin coating technique on the quartz or silicon substrates and pyrolyzed at different temperatures from 225 degrees Celsius to 1000 degrees Celsius. The semiempirical quantum mechanics calculations were performed and the results were compared with experiment.

The effect of molecular adsorbates on the luminescence properties of the conventionally prepared porous silicon and silicon nanoparticles was studied. The effect of simple adsorbates (O₂, H₂, N₂) on the annealed porous Si does not restore red luminescence and gives rise to a weak emission in the violet region. The luminescence reappeared under adsorption of water vapor on the samples. Under the ultra high vacuum conditions from nanoparticles electroluminescence was not observed. The red luminescence of porous Si can be caused by water molecules (together with all possible kinds of impurities) adsorbed in the pores. The porous Si layer can serve as a natural self filter for the emitted light.

Electroluminescence and electron emission from dispersed (island) Si films excited by the conduction current are investigated. These phenomena are observed after the reduction of the Si work function by adsorbed BaO molecules. The results are compared with similar data obtained for porous Si samples. A strong effect of adsorbed layers on the photon and electron emission is found.

The optical properties of sol-gel glasses doped with Er³⁺ ions are presented. Samples of regular silica glass and glass prepared with a small amount of Al₂O₃ were investigated. It was found that the sample with Al₂O₃ exhibits emission at 1.53 micrometer. Such material can be used for construction of an efficient fiber amplifier. In this paper we present the absorption and emission spectra of both samples. The effect of co- dopants and temperature on optical properties is also discussed.

Conventional methods of solid state laser pumping use the broad spectrum output obtained from flashlamps and it leads to an inefficient system requiring cooling. The use of diode lasers as pump sources offers a potentially huge increase in overall efficiency coupled with the compactness and reliability usually associated with solid state devices. Spectral analysis of the absorption pumping bands for four neodymium doped laser materials was measured. The spectrum of emission radiation of the thermally tunable diode laser was matched for these materials.

The second harmonic generation (SHG) of laser diodes is an attractive way of obtaining short- wavelength, coherent light in the blue spectral range. Conversion into second harmonic can be performed directly in non-linear crystal. The second harmonic generation from 1 watt, 980 nm diode laser in non-linear crystal LiIO₃ was obtained. Description of experiments and results is presented.

This paper illustrates the application of microscopy techniques to investigate various material processing and device-related problems that one encounters in the development of semiconductor laser diodes. General comments are made concerning local characterization of semiconductors. Various laser reliability/degradation issues are addressed. As an example of how microscopy techniques facilitate the building of modern lasers, the application of the ordering phenomenon is discussed.

Single-mode waveguide Y-junctions are important elements of integrated optical circuits. These branching devices are used to divide or to combine optical power, and applications include beam splitters, interferometers and switches. This work presents a brief review of different types of Y-junctions and methods used for analyzing these types of structures. The computation model has been created and approximate analysis performed. The dependence of the operation characteristics on the geometrical parameters is discussed and the design algorithm useful in construction of this type of structure is presented. The procedure for successful production of Y-junctions in GaAs/AlGaAs waveguides is also given.

Semiconductor light sources and detectors keep the major share of the telecommunication and local area network market. Diode laser and detector structures are also massively produced in the course of many application and research projects. Usually research work includes: understanding physical phenomena governing device performance, device modeling and fabrication. A number of steps however, have to be completed before one can use the device in a real-life system or sell it. To exemplify details of fiber optic detectors and transmitters fabrication, a didactic-purpose fabrication line has been assembled. The following paper presents results of a project aimed at producing some fiber optic telecommunication devices during students laboratory work.

Silica glasses are important materials for laser application because of high thermal resistance and relatively lower non-linear refraction index than in silicated glasses. A new preparative technique for obtaining silica gel-glasses is presented. This technique permits us to prepare the silica glasses at low temperature. The preparation of silica gel-glasses with a small contamination of OH and CH maoities is possible by baking the samples in F₂ or Cl₂ atmosphere. The obtained glass rods were then drawn into fibers. The fiber attenuation was measured on 200 micrometer core diameter fibers using the cut-back technique and in agreement with the IEC 875-1 norm. It was found that the new glass has much lower attenuation characteristics at 1.55 micrometer. We believe that optimization of sol-gel processing will completely eliminate water impurity absorption.

Instead of classic beam-splitters, the fiber couplers were used to detect the laser heterodyne signals. The heterodyning of two linearly polarized laser beams introduced into the gradient index fiber couplers was observed and analyzed.

We examine crystals belonging to two wide families of compounds of general chemical formulae ABC₃O₇ and ABCO₄ (A equals Ca, Sr, Ba; B equals Y, La-Gd; C equals Al, Ga) which appear to be promising active materials for the design of all-solid-state lasers. Inhomogeneous broadening of spectral lines influences weakly the extraction efficiency in the case of SrLaGa₃O₇:Nd and BaLaGa₃O₇:Nd but it is found to be a limiting factor controlling the performance of SrLaAlO₄:Nd laser. Preliminary spectroscopic study indicates that chromium doped SrLaAlO₄ and SrLaGaO₄ may be promising active materials for the design of tunable infrared lasers.

The atomic force microscope (AFM) is a very sensitive instrument to examine the topography of surfaces and their properties. The sensitivity of the AFM depends on the choice of the detector system, which is used to observe the cantilever deflection. A cantilever with integrated Wheatstone piezoresistive bridge as a deflection sensor was used in experiments. We describe noise properties of the piezoresistive Wheatstone bridge cantilever and show examples of topography measurements in contact and noncontact mode.

In the article, the results of investigation of the silicon microtips manufacturing process are presented. A two-stage technology of the microtips forming has been worked out. At the first stage, a single-micrometer high, suitably shaped precursor of the tip is done. Next, the process of its sharpening is performed, using the isotropic etching and thermal oxidation techniques. The arrays of the reproducible silicon microtips were fabricated.

Amorphous, hydrogenated carbon thin films have been prepared in an rf supported plasma process including ferrocene as an organometallic. Differences in electrical conductivity and elastic modulus are suggested to be due to a modification of the carbonaceous matrix. For locally resolved measurements of the electrical conductivity an atomic force microscope working in the contact mode has been employed.

The procedure for three-dimensional lithography with electron-beam induced deposition is described. The technique can be applied in scanning electron microscopes and does not contaminate the instrument. Various precursor materials with vapor pressures of mtorr at room temperature are investigated with regard to their suitability for different applications. Deposited materials are characterized with respect to topography, morphology, electrical and optical properties by scanning electron microscopy, high resolution transmission electron microscopy, conductivity measurements, and energy dispersive x-ray analysis. The results show, that the properties of deposited nanocrystalline materials can be selected to be insulating or conducting using different currents and voltages for the deposition process. High resolution and high aspect ratio structures are grown with this technique and are applied in many fields. In optics 2-dimensional phonon crystals can be custom designed and produced as filters with a narrow bandgap. For atomic force and scanning tunneling microscopy very fine tips having a high aspect ratio are produced on top of conventional commercial probe tips, or on thermally heated etched tungsten tips, or on fresh cut wire tips. Nanostructurization of materials renders deposited nanocrystalline gold dots of 20 nm diameter and 10 nm distance. K(Omega) to G(Omega) -resistors of a few micrometer in length are components for micro- and nanoelectronics. Electrodes and field electron sources for electron optical microsystems are built under computer control. A micro-tube of 0.25 micrometer in length can be built for vacuum microelectronics.

This contribution is concerned with the question of if the scanning tunneling microscope (STM) or possibly its relatives out of the group of the diverse scanning probe microscopes (SPM) developed in recent years are reliable tools for atomic scale -- or at least nanometric -- modifications of solid state surfaces or for building structures on it, especially for various purposes like (1) high-density memory storage, (2) nanolithography, or more general: (3) nanofabrication and (4) atom and molecule manipulation. From these points of view the last years results are reviewed.

The aim of this work was to elaborate an all-purpose driving and imaging software for scanning microscopes.

Au films were evaporated on cleaved mica substrates at various temperatures. Morphology of epitaxial films was observed by scanning tunneling microscope (STM) under non-vacuum conditions. An influence of substrate temperature on a film has been studied and temperature dependence of surface roughness with a local minimum at temperature 0.6 Tm (Tm equals 1333 K -- temperature of melting point of Au) was found.