Basic Electrical Properties Research Articles

Electrical Properties of Silicon Dioxide Films Fabricated at 700°C: III . High Pressure Thermal Oxidation

High quality thermal oxides of silicon have been fabricated on silicon substrates over the oxidation temperature range 635°–1100°C. Dry, high pressure oxidation (DRYPOX) was used to grow oxides at temperatures below 1000°C. The high pressure range investigated was 2–500 atm. Standard capacitance‐voltage techniques have been used to characterize these oxides in terms of oxide fixed change and interface trap densities . Additionally, avalanche injection of both electrons and holes has been used to evaluate the charge trapping properties of these films. The electron trapping properties of 685°C, high pressure oxides were compared with “conventional” 1000°C oxides fabricated at 1 atm and with oxides fabricated using low pressure chemical vapor deposition (LPCVD) at 730°C. The results of these experiments were as follows: (i) basic electrical properties of high pressure oxides, as well as hole and electron trapping behavior in these oxides, were similar to those of 1000°C conventional oxides; (ii) hole trap densities exhibited a broad minimum at an oxidation temperature between 800° and 900°C; and (iii) electron trapping behavior in 685°C DRYPOX oxides was markedly superior to that in 730°C LPCVD oxides. The LPCVD oxide required an anneal at 1000°C to produce electron trapping characteristics comparable to those of DRYPOX samples processed entirely at temperatures below 700°C.

Directional crystallization of CdHgTe in microgravity conditions

Two experiments on crystallization of Cd 0.22Hg 0.78Te mixed crystals from the liquid phase were performed on the Salyut 6 Space Laboratory. The rates of growth varied in time from 2 mm/h to 50 mm/h. The properties of the crystals were found to be strongly dependent on the growth rate. For slow rates of crystallization, diffusion-controlled growth took place and homogeneous material was obtained. For rates higher than 3 mm/h spontaneous crystallization began, creating cavities which gave rise to further inhomogeneities in the material. In this paper the crystallization process is described and data on some basic structural and electrical properties of the space-grown crystals are presented together with the results of composition and surface morphology studies. A new effect, the formation of a surface layer about 30 μm thick and differing in composition from the bulk material, was discovered. The electrical properties of the crystal showed no apparent effect of zero-gravity conditions on deviations from stoichiometry.

Deposition of In 2O 3SnO 2 layers on glass substrates using a spraying method

Thin films of doped indium oxide (In 2O 3) or of tin oxide (SnO 2), as well as mixed compounds of the two (indium tin oxide (ITO)), can be prepared in a highly conductive form with the important property of being highly transparent in the visible and near-IR regions of the solar spectrum. Moreover, these layers are physically and chemically resistant and adhere well to many substrates. Potential applications are numerous: specifically as coatings for heat mirror systems as well as in solar cell technology. The “spraying” method of preparation uses a hydrolysis reaction at relatively low temperatures (400–600 °C) in an alcoholic solution of tin or indium chloride. The basic physical, electrical and optical properties of the films are reviewed in relation to the dopant concentrations and stoichiometric deviations. (Typical parameters for ITO are resistivity ϱ≈5×10 −4 ohms cm, transmission coefficient T≈80–90% in the wavelength range 0.3–1.5 microm and sheet resistance R □≈10 ohms.) In recent years the economic contingencies related to the energy crisis have led to an increase of interest in these layers, but the marked rise in the number of publications does not correspond to concomitant improvements in layer quality or to a better understanding of the properties. Some basic theoretical limitations can be pointed out: electron-hole pair creation limits transparency at short wavelengths and the steep increase of reflectivity due to free carrier absorption limits it at long wavelengths. The latter factor is directly related to the electrical conductivity. A fundamental conflict between transparency and conductivity is therefore built in. The properties of these layers are compared with those of chemically identical layers prepared by different methods, as well as with those of some other transparent and conducting films of quite different compositions.

Sampling membrane potential, membrane resistance and electrode resistance with a glass electrode impaled into a single cell

A method is demonstrated to measure membrane resistances and membrane potentials of single cells during impalement by a single glass microelectrode. The intention was to develop a procedure which would provide data almost continuously. Therefore, a frequency-dependent voltage divider network has been chosen to represent the basic electrical properties of the electrode and cell membrane, and used to explore its voltage response to a current stimulus, consisting of two rectangular pulses of different widths. It can be shown that the resolution of the method can be improved by inverting this stimulus so that each polarization becomes a relaxation and vice versa. In order to generate, analyze and display this signal continuously, a device has been designed which has been called ‘Electrophysiological Monitor, (ElM2)’. ElM2 provides a current stimulus as input into a standard bridge network and can analyze the summed response of the electrode and cell by a set of sample-hold amplifiers. It then decodes and displays the data continuously, as membrane potential (Em), input resistance of the cell (Rinp) and the electrode resistance (Re) respectively. From Rinp the membrane resistance (Rm) can be deduced. The validity of the method has been examined by measuring these parameters in frog muscle cells. Technical design considerations, the accuracy and possible pitfalls with the suggested procedure are discussed.

Preparation and basic electrical properties of CdTe thick films

Results of I–U characteristics, C–U dependences, impedance and phase angle measurements, and microscopic measurements on n- and p-type CdTe films allow to construct the following model of the film. The film is composed of conductive grains separated by more resistive intergranular (IG) regions with barriers on interfaces. The space charge regions are formed in grains and in IG regions. The barriers are formed in consequence of localized states on grain–IG regions interfaces and the diffusion across the barriers is the dominating mechanism for transport of charge in the film at 2 to 5 V. The equivalent circuit of the film represents a series chain composed from elements containing parallel (RC) circuits with series resistances R0. R0's correpsond to the resistance of neutral bulk of grains and IG regions, parallel RC terms correspond to space charge regions. The frequency dependence of capacity of these regions is caused probably by inertial charge accomodation by localized states on grain---IG regions interfaces, or inside the IG regions. Also the form of Cole-Cole plots can be explained by presence of these states and corresponds to a symmetrical distribution of relaxation times of the interface states. [Russian Text Ignored]

Classes of Light-Evoked Response in the Retina of Strombus

ABSTRACT Two general classes of light-evoked responses were recorded intracellularly from the retina of Strombus luhuanus. In one class, retinal illumination caused depolarization, the amplitude of which was graded with light intensity. In the other, it produced hyperpolarization and concomitant inhibition of repetitive action potentials. There were two types of depolarizing waveform. Each was associated with a different type of intracellular recording site, characterized on the basis of electrical properties in the dark. In general, the type of response with a more rapid rate of decay was recorded from a site which exhibited a lower resting potential, higher input resistance, and longer ‘membrane charging time. ‘ The two depolarizing responses and the hyperpolarizing response apparently each arose from a different type of neurone. The depolarizing types, at least one of which is a photoreceptor, apparently give rise to the cornea-negativity of the electroretinogram and ‘on’ activity in the optic nerve fibres. The hyperpolarizing type apparently mediates ‘off’ activity in the optic nerve..

Properties of thyroidectomized rat extensor muscle.

Basic mechanical and electrical properties of rat extensor muscle were analyzed 4--6 wk after thyroid removal. Isometric twitch tensions in thyroidectomized (Tx) rat muscle varied considerably, with over 60% of the muscles showing abnormally low values and the remainder showing a high twitch force. The duration of the twitch was significantly increased from 137 to 245 ms but contraction and half-relaxation times were not significantly changed. Tetanic force was not effected by thyroidectomy. Electrical properties of the muscle fiber membranes were made exclusively via intracellular techniques. The resting membrane potential was slightly higher in thyroidectomized rats (-79 mV) as compared to sham controls (-78 mV). Both direct and indirect action potentials showed higher overshoots, amplitudes, and rates of depolarization in thyroidectomized rats. The threshold of the indirect action potential appeared at a higher transmembrane potential as compared to sham-operated controls. The input resistance, space constant, time constant, and specific membrane resistance were all significantly increased in thyroidectomized rat extensor muscle, whereas fiber diameter and capacitance were significantly decreased. Estimates of specific ionic conductance show that both potassium and chloride conductance are decreased in thyroidectomized rat muscle.

2.7 Deposition methods for dielectric films and their electrical properties

The various methods of depositing thin (<1 ωm) dielectric films are summarized. This summary is followed by a brief survey of the basic electrical properties and also of the applications of thin dielectric films with particular reference to deposition techniques. It is concluded that it is not possible to give a ‘best buy’ for a preparation method, as so much depends on the electrical studies to be made or the applications which are envisaged.

Basic electrical properties of tight epithelia determined with a simple method.

A simple method for the routine mounting of epithelia which greatly reduces or eliminates faulty sealing at the edge is described. The values of potential and resistance observed in the frog skin and toad urinary bladder are comparable to those found with more complicated methods designed to minimize edge damage. In agreement with observations in other epithelia, a direct relationship between short circuit and conductance is observed for frog skin and toad urinary bladder, implying that the relationship is a general feature of tight epithelia. Furthermore, the high values of transepithelial resistance imply that the lower limit for the paracellular shunt pathway resistance should be reset upwards.

The Basic Reactions, Compositions, and Electrical Properties of Pd-Ag Thick-Film Resistors

The basic reactions, compositions, and electrical properties of glazed Pd-Ag sintered layers through a firing process have been examined by differential thermal analysis, thermograviometric analysis, and X-ray diffraction analysis. The evaporation and combustion of screening vehicle and solvents, the oxidation-reduction behaviors of Pd and Ag the creation of PdAg solid solution, and the electrical properties and stability of these resistors have been studied. From these tests it was found that the degree of process sensitivity for these resistors was high, and electrical properties and stability of these resistors were affected in much the same way by firing temperature and firing period. They were influenced most by temperature rise rate and least by temperature fall rate.

Influence of substrate temperature on basic electrical properties of CdSe thin films

The influence of substrate temperature in the range 25°–200°C on the basic electrical properties of CdSe thin films has been studied and a comparison with the results of other authors and with the electrical properties of CdSe thin films annealed in oxygen and selenium vapours has been made. It is shown that in the temperature range in which the grain size of the film does not change with the substrate temperature, the film resistivity increases with increasing substrate temperature while the carrier concentration decreases monotonically; the effective Hall mobility has a more complicated dependence, exhibiting a maximum at a temperature of about 40°C. By analysing the carrier excitation mechanism it is proposed that in the films studied three donor excitation levels exist, the first one ( ΔE=0.025 eV) corresponding to the impurity atoms, and the second ( ΔE=0.14 eV) and third ( ΔE=0.4 eV) to the divalent selenium vacancies. The donors are assumed to be compensated by some acceptor centres. The model allows the great variety in n m=f(1/ T) curves to be explained and gives useful information about the carrier excitation mechanism involved.

Metal-ceramic constraints for multilayer electronic packages

Ceramic formulations set in an organic binder are currently being cast in thin paper-like sheets. These sheets may be punched, screened with metal pastes, and laminated to form a composite of metal and ceramic particles held together by an organic medium. By slowly burning off the organic binder and then sintering the ceramic and metal together, a substrate with many layers of interconnecting wiring may be obtained. The coincident sintering of the ceramic and metal phases presents compatibility constraints. Temperature considerations with respect to shrinkage and coefficient of expansion match between the ceramic and metal phases as well as solid/solid and solid/ambient interactions are important constraints in the fabrication of these composites. High conductivity metals (e.g., Ag, Cu) are generally not available for co-firing because sintering temperatures of important ceramic formulations are higher than the melting points of these metals. This constraint has been minimized through the use of capillary infiltration of molten metals into the ceramic structure. Consequently, it is now possible for multilayer ceramic structures to provide the interconnection wiring densities and conductivities necessary to respond to the needs of greater circuit densities of integrated circuit chips. Material selections are reviewed on the basis of electrical properties, ambient interactions, stresses due to sintering shrinkage, and thermal coefficient of expansion. Certain problems, tradeoffs, and procedures used in the fabrication of a multilayer substrate with Cu-filtrated lines are discussed.

Cell for Measurement of Basic Electrical Properties of Amorphous and Polycrystalline Materials under Pressure

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A study of the solid state-gaseous phase equilibrium in CdSe and its application to the growing of single crystals from the gaseous phase by Frerich's method

The equilibrium between the solid state and the gaseous phase of the semi-conducting compound CdSe is investigated. This is a study of two equilibrium reactions CdSe(s)⇄Cd(g) + + (1/2) Se2(g) and Se6(g)⇄3 Se2(g) as a function of the temperature. The results were used to estimate the optimum conditions for the growing of CdSe single crystals from the gaseous phase by Frerichs' method. The basic electrical and optical properties were then measured on the crystals. In conclusion the results of the experiments are evaluated and compared with those of other authors.

Some observations and theories concerning the electrical behavior of heart muscle

ELECTROPHYSIOLOGY of heart muscle may be considered the science of the nature and propagation of electrical energy produced by heart muscle fibers submerged in a conducting medium. It deals with the generator and the medium but, at least for the purpose of this review, not with the problems of lead fields, lead placement, lead systems, or with the representation of projected cardiac electromotive forces on the body surface . It forms a basis, as yet incomplete, for a rational interpretation of an electrocardiographic curve or vectocardiographic figure . This survey is intended merely to highlight general principles and certain interrelationships . It will be concerned with (1) the basic electrical properties of heart muscle fibers, (2) the quantity and distribution of electrical forces over cardiac musculature, and (3) the distribution of electrical forces in volume conductors . Recent monographs should be consulted for more detailed discussions [1-10] . ELECTRICAL PROPERTIES OF CARDIAC FIBERS . Some physiological aspects of subcellufar structure : The cardiac cell is excitable tissue, i .e ., upon appropriate stimulus a transient change in the physicochemical properties of the cell occurs permitting alterations in ionic transfer across its boundary . The effect is usually all or none, and the disturbance is generally propagated from cell to cell . Heart muscle shares this property with nerve tissue, skeletal and smooth muscle . There are certain fundamental similarities between the electrical behavior of all excitable cells so that information gained from one can be applied to the others . There are also important dissimilarities, apparently related to the specific function of individual tissues . Since most information concerning the cellular events of excitable systems so far has been derived from nerve cells, the laws which define electrical behavior in nervous tissue are used as the prototype . Such cells resemble cables or telephone wires with one long (infinite) axis and one of relatively short diameter . For many years the cable theory of electrical conduction developed by Thomson (Lord Kelvin) in 1856 has been applied to biologic systems of this general kind [14,27] . The short, thick, grossly syncytial heart muscle fiber is a structure of greater complexity than nerve . This modifies some of the assumptions made from the study of nerve cells . Whether or not heart muscle can be considered truly syncytial in nature depends on one's point of view. Heart muscle fibers are interrupted by light-refractile bands which traverse the fiber from fibril to fibril . The function and properties of these intercalated discs are considered by some to be consistent with the existence of an absolute cell boundary [89] . They are the starting and terminal points of insertion of the myofibrils, and in a mechanical sense these structures can be considered boundaries . Electrical resistance across the discs, however, is not high [8], which may be accepted as evidence in favor of at least a functional syncytium. There are differences in electrical responses of heart muscle fibers from different species, perhaps simply related to the modifying effects of temperature and heart rate, and there are qualitative and quantitative differences in the electrical behavior of various areas within a single heart . These differences should have their morphologic counterpart . As yet little is known of submicroscopic details of cardiac tissue on which

Semiconductor Properties of Recrystallized Silicon in Aluminum Alloy Junction Diodes

This is a study of the basic electrical properties of thin recrystallized regions formed in the fabrication of PN junctions by the alloying of pure aluminum on N-type silicon single crystals. The average aluminum concentration is about 7×1018 cm−3, and varies by a factor of 4 to 5; being largest in the region first recrystallized and decreasing in a linear manner to the surface immediately beneath the aluminum-silicon eutectic. The average Hall-hole mobility is about 55 cm2 volt−1 sec−1 and varies from 35 to 75 cm2 volt−1 sec−1 across a region formed by precipating from 977°C to the eutectic. Across the same region the conductivity varies from 72 to 35 mho cm−1. The built-in field which is both a function of depth and total width can vary from 10 to 200 v per cm in typical cases. The minority carrier (electron) diffusion length ranges from 4 to 12 μ. The temperature dependence of the distribution coefficient corresponds to an enthalpy change (differential heat of solution) of +0.43 ev necessary for the transfer of an atom of aluminum from the liquid to the solid.

Solar batteries On the direct conversion of radiation into electrical energy by means of photoelements

The possibilities are examined of direct conversion of the energy of solar radiation into electrical energy by means of semiconductor photoelements. The basic electrical and optical properties of germanium and silicon crystals are briefly described, as well as methods of producing them and regulating their electrical properties by the introduction of small amounts of “dope.” The principles of the action of photoelements are examined and the basic parameters determining their spectral sensitivity and efficiency are discussed. Data are adduced on the functioning of experimental solar batteries used as generators.

The properties and manufacture of piezoelectric quartz crystals

The paper discusses the basic electrical properties of quartz crystals, such as frequency stability, temperature coefficient and activity. Their relationship to the actual frequency of oscillation of a crystal oscillator is described and some typical figures given.

Standing potential correlates of hypnosis and narcosis.

ALTHOUGH more than 150 years have elapsed since Galvani first associated electricity with living systems, accurate determination of electrical phenomena did not occur until relatively recent times. With the advent of electrocardiography and electroencephalography, A.C. potentials could be successfully detected; D.C. determinations, however, were beset with numerous difficulties, transcended only in the past few years. To validate the concept that living organisms consist of electrical fields, Burr, with the assistance of Lane and Nims, 1 perfected a microvoltmeter by means of which basic electrical properties of living systems can be measured. Experiments of the past 16 years have clearly demonstrated that in vertebrates, invertebrates 2 and plants 3 there is a relatively steady, stable voltage gradient of considerable magnitude between any two points—altered only by changes in the fundamental biology of the organism—which exists in well defined patterns characteristic of the species and to some extent characteristic of the individual.