Showing papers on "Conductivity published in 1970"
TL;DR: In this article, the experimental evidence concerning the density of states in amorphous semiconductors and the ranges of energy in which states are localized is reviewed; this includes d.c and a.c. conductivity, drift mobility and optical absorption.
Abstract: The experimental evidence concerning the density of states in amorphous semiconductors and the ranges of energy in which states are localized is reviewed; this includes d.c. and a.c. conductivity, drift mobility and optical absorption. There is evidence that for some chalcogenide semiconductors the model proposed by Cohen, Fritzsche and Ovshinsky (1969) should be modified by introducing a band of localized states, near the centre of the gap. The values of C, when the d.c. conductivity is expressed as C exp (- E/kT), are considered. The behaviour of the optical absorption coefficient near the absorption edge and its relation to exciton formation are discussed. Finally, an interpretation of some results on photoconductivity is offered.
3,465 citations
TL;DR: In this article, the dc and ac conductivities and thermoelectric power have been measured as a function of the ratio (V 4+ /V total ) in glasses in the system V 2 O 5 -P 2 O5.
Abstract: The dc and ac conductivity and thermoelectric power have been measured as a function of the ratio (V 4+ /V total ) in glasses in the system V 2 O 5 -P 2 O 5 . The conductivity goes through a maximum as the ratio (V 4+ /V total ) is varied but at a much lower value than that expected from a straightforward hopping model (i.e. 0.5) in which all sites contribute equally. The thermoelectric power tends to go through zero but at a different value of (V 4+ /V total ) than the maximum in conductivity. These discrepancies from simple behaviour may be connected with the structural complexity of the glass and at least two suggestions can be made to account for these deviations. The log conductivity versus (1/ T ) plots are not linear and their slopes decrease rapidly at low temperatures. Possible reasons for this behaviour are mentioned. The ac conductivity varies nearly linearly with frequency in the audio- to radio-frequency region and approximately as the square of frequency at higher frequencies. At the same time the high frequency conductivity tends to become independent of temperature. This is almost identical with similar observations in, for instance, chalcogenide glasses.
222 citations
TL;DR: In this paper, electrical conductivity without particle-particle or waveparticle collisional noise or radiation was shown to be achievable without particle particle particle or wave particle collimation.
207 citations
TL;DR: In this article, the authors show that Imidazole single crystal has a highly anisotropic conductivity; the ratio of conductivity in the c and a crystallographic directions is ∼103, and the limiting conduction process is possibly due to L−defect injection and transport back down the hydrogen bonded chain after the proton is discharged.
Abstract: Imidazole single crystal has a highly anisotropic conductivity; the ratio of conductivity in the c and a crystallographic directions is ∼103. In the c crystallographic direction, the hydrogen bonded direction, protonic carriers are discharged as hydrogen at the negative electrode. The limiting conduction process is possibly due to L‐defect injection and transport back down the hydrogen bonded chain after the proton is discharged. Conductivity in the a direction is probably electronic and extrinsic.
177 citations
TL;DR: In this article, the authors used the hopping model and small polaron theory to understand the mechanism of conduction in rare earth sesquioxides and nonstoichiometric oxides of rare-earths.
97 citations
TL;DR: In this article, thermal conductivity measurements of two frozen soils, Leda clay and Sudbury silty clay, taken at temperatures between 0 and −22 °C by means of a thermal probe and a transient heat flow technique, were performed.
Abstract: Thermal conductivity measurements of two frozen soils, Leda clay and Sudbury silty clay, taken at temperatures between 0 and −22 °C by means of a thermal probe and a transient heat flow technique, ...
87 citations
TL;DR: In this paper, the frequency dependence of conductivity at room temperature has been measured for amorphous films of As2Te3, Te2AsSi, and a composition containing Te, As, Si, and Ge.
Abstract: The frequency dependence of conductivity at room temperature has been measured for amorphous films of As2Te3, Te2AsSi, and a composition containing Te, As, Si, and Ge. Results were similar for the three compositions. The conductivity could be considered to consist of two components, a frequency independent component σ0 and a frequency dependent component σ1; the latter varied as ωs with s usually around 0.8 to 0.9. The component σ1 attained a magnitude comparable to σ0 at 105 to 106 Hz, except in the case of point contacts with light contact pressures, where capacitive coupling increased the magnitude of σ1 relative to σ0. The component σ1 is attributed to a hopping mechanism and σ0 is attributed to intrinsic band conduction. Optical data for the fundamental absorption edge is also included.
85 citations
TL;DR: The electrical conductivity of pure KI, KI+SrI2, and KI + K2CO3 single crystals was measured as a function of temperature in this paper.
Abstract: The electrical conductivity of pure KI, KI + SrI2, and KI + K2CO3 single crystals was measured as a function of temperature. A method for calculating ionic transport parameters from these results w...
78 citations
TL;DR: The electrical conductivity of a family of amorphous thin films, evaporated from semi-conducting alloys containing Si, Ge, As, Te and S as principal constituents, has been studied between 77 and 500°K as discussed by the authors.
Abstract: The electrical conductivity of a family of amorphous thin films, evaporated from semi-conducting alloys containing Si, Ge, As, Te and S as principal constituents, has been studied between 77 and 500°K. After deposition, these films show an intrinsic conductivity σ(T) = σ0 exp(−ΔE/kT), with σ0 ∼ 102–103 (gW-cm)−1 and ΔE ∼ 0.4–0.6 eV. Subsequent thermal cycling to temperatures near 500°K first produces a region of extrinsic conductivity at low temperatures, without appreciably affecting the optical absorption edge; and then produces rapid devitrification. At applied fields in excess of ∼104 V/cm the conductivity becomes superohmic, varying approximately as σ(T) exp (V/V0), where V0 is also a weak function of T. An additional non-ohmic regime appears at temperatures below 200°K.
74 citations
TL;DR: In this article, the transport coefficients of the ionospheric electron gas, including thermal conductivity, electrical conductivity and current flow conductivity due to thermal gradients, were evaluated.
71 citations
TL;DR: In this paper, the authors report measurements of electrical conduction in thin films of amorphous carbon and show that resistivity becomes independent of temperature at very low temperatures, and for this they have no adequate explanation.
Abstract: We report measurements of electrical conduction in thin films of amorphous carbon. The magnitude of the conductivity varies greatly from sample to sample. At low fields the current is always linear in voltage and shows the temperature dependence which is characteristic of the Mott hopping mechanism. At high fields conduction appears to be by the Poole-Frenkel mechanism with a range of trap depths and a large effective dielectric constant. In the case of conduction through thin carbon films the resistivity appears to become independent of temperature at very low temperatures, and for this we have no adequate explanation.
TL;DR: In this article, the authors present their observations on induced conductivity transformation from one state to another, and relate their results to those obtained from calorimetric and structural investigation on the same materials.
Abstract: Certain amorphous chalcogenide alloys, such as Ge15Te85, exhibit metastable conductivity. These reversible structural changes in amorphous alloys entailing variation in order and conductivity have been made the basis of memory devices.(1) In this paper, we present our observations on induced conductivity transformation from one state to another. Because the conductivity involves structural changes in the bulk we relate our results to those obtained from calorimetric (2) and structural investigation (3) on the same materials. We also present measurements on the electrical characteristics of memory switches.
Patent•
25 May 1970TL;DR: In this paper, an electro-optical device is provided which is useful in control of visible and infrared absorption by windows, data display devices and the like typically comprising in sandwich arrangement a pair of electrodes, and disposed therebetween, two identical layers of transition metal electrochromic compounds separated by a semi-solid highly conductive sulfuric acid gel electrolyte.
Abstract: An electro-optical device is provided which is useful in control of visible and infrared absorption by windows, data display devices and the like typically comprising in sandwich arrangement a pair of electrodes, and disposed therebetween, two identical layers of transition metal electrochromic compounds separated by a semi-solid highly conductive sulfuric acid gel electrolyte. The gel exhibits good conductivity, stability and compatibility with the electrochromic layers.
TL;DR: In this paper, the electron and hole trapping levels of high density of states determine essentially the conductivity mechanism of β-rhombohedral boron, and the ionization energy of trapped electrons is much greater than that of trapped holes; so, up to high temperatures, the electrons do not appreciably contribute to the charge transport.
Abstract: Electron and hole trapping levels of high density of states determine essentially the conductivity mechanism of β-rhombohedral boron. The ionization energy of trapped electrons is much greater than that of trapped holes; so, up to high temperatures, the electrons do not appreciably contribute to the charge transport. From electrical conductivity and thermoelectric power at higher temperatures one obtains the activation energy of the hole mobility (0.19 eV). At low temperatures hopping within the hole trapping level seems to be the prevailing conductivity mechanism.
TL;DR: In this article, the diffusion of oxygen in UO2+α was measured between 600° and 1100°C and the relation between total conductivity and average O/U ratio was derived, and the diffusion coefficients were obtained.
Abstract: The diffusion of oxygen in UO2+α was measured between 600° and 1100°C. Samples with initial O/U values 2.08 and 2.04 were reduced in hydrogen; reduction was monitored continuously by electrical conductivity measurements. The relation between total conductivity and average O/U ratio was derived, and the diffusion coefficients were obtained. The validity of the electrical conductivity vs O/U relation was checked by measuring weight loss during reduction. Diffusion-controlled kinetics were confirmed by oxygen gradient measurements. The oxygen chemical diffusion coefficient is given by D= 0.5 exp - This equation agrees with previously determined values of the oxygen chemical diffusion coefficient of UO2+α.
TL;DR: The radiation-induced conductivity in liquid neopentane was studied at electric field strengths up to 140 kV/cm and the total ionization yield agrees with the gas-phase value.
Abstract: The radiation-induced conductivity in liquid neopentane was studied at electric field strengths up to 140 kV/cm. The shape of the ionization current vs. field strength curve is quite different from that of n-hexane. Extrapolation to infinite field strength gives a total ionization yield of G = 4.03 (W = 24.8) which agrees with the gas-phase value.
TL;DR: In this paper, normal and para-hydrogen conductivity measurements at temperatures from 200 to 17 deg K, at densities up to 2.6 times critical density, and at pressures to 15 MN/sq m are made.
Abstract: Normal and para-hydrogen conductivity measurements at temperatures from 200 to 17 deg K, at densities up to 2.6 times critical density, and at pressures to 15 MN/sq m are made. Using new calorimeter, data are analyzed as functions of density at fixed temperatures and of temperature at fixed densities
TL;DR: In this paper, the high frequency conductivity of vitreous arsenic selenide was measured in the frequency range of 5 × 104 to 3 × 107 Hz and in the temperature range from room temperature up to 150°C.
Abstract: The high-frequency conductivity of vitreous arsenic selenide was measured in the frequency range of 5 × 104 to 3 × 107 Hz and in the temperature range from room temperature up to 150°C. It is found that the conductivity increases as σ ∼ ωα, where α < 1. Based on the results obtained, a conclusion is drawn that the conductivity mechanism in this material is due to hopping.
TL;DR: The existence of the ionic layer is supported by a c conductivity calculated from dielectric loss vs. 1/T curve and also by the current maximum in the current-time curves after the reversal of applied voltage polarity as mentioned in this paper.
Abstract: The relation between d c conductivity evaluated from one-minute current after a voltage application and reciprocal temperature bends notably above 50°C supposedly due to an ionic layer build-up near an electrode and also due to the clean-up of charge carriers. The existence of the ionic layer is supported by the a c conductivity calculated from dielectric loss vs. 1/ T curve and also by the current maximum in the current-time curves after the reversal of applied voltage polarity. The apparent activation energy of conduction E c is about 23 kcal/mole. The mobility of charge carriers is estimated (µ≃2×10 -8 cm 2 /volt. sec at 102°C) from an initial slope of current-time curves assuming the clean-up effect of charge carrier and its activation energy E µ is obtained as 16 kcal/mole. The difference of E c and E µ may give rise to a discussion of the origin of ions.
TL;DR: The anomalous behavior of chalcogenide-glass switches, in the thin-film limit, is incorporated into the electrothermal switching model by taking account of both temperature and field dependences of the electrical conductivity as mentioned in this paper.
Abstract: The anomalous behaviour of chalcogenide-glass switches, in the thin-film limit, is incorporated into the electrothermal switching model by taking account of both temperature and field dependences of the electrical conductivity. Calculations of the critical field as a function of temperature and thickness are compared with experimental observations.
TL;DR: In this paper, the authors measured the thermal conductivity, λ(80° to 400°K), electrical resistivity, ρ(4.2° to 300°K) and absolute Seebeck coefficient of pressed and sintered uranium mononitride.
Abstract: Measurements are reported for the thermal conductivity, λ(80° to 400°K), electrical resistivity, ρ(4.2° to 400°K), and absolute Seebeck coefficient, Q(6° to 400°K), of pressed and sintered uranium mononitride. The measurements between 77° and 400°K were made using an absolute longitudinal heat flow apparatus. These data and literature values for the thermal conductivity and electrical resistivity at higher temperatures were used to separate the electronic and lattice portions of the thermal conductivity. The results indicate that the lattice conductivity peaks in the range 250° to 300°K and that the high-temperature limit of the Lorenz function may be greater than the Sommerfeld value of 2.443 × 10-8 (V2°K-2). The electrical resistivity and the absolute Seebeck coefficient exhibit sharp slope changes near the Neel temperature, TN(∼50° to 60°K). The Seebeck coefficient has a minimum at 34°K and then rises to a local maximum at 10°K. This low-temperature peak is probably due to magnon drag. The temperature dependence of the electrical resistivity is dominated by the magnetic contribution which increases as T2.38±0.08 between 10° and 52°K. The magnetic contribution is constant at high temperatures with an estimated value of 142 μΩ-cm.
TL;DR: In this article, the influence of the morphology and size of the AgBr grains and the addition of stabilizing agent on the conductivity of Agbr grains was detected in a simple manner.
Abstract: Dielectric measurements effected on silver bromide emulsions in the frequency range 102−107 Hz show a maximum in the absorption curve. This dielectric absorption is interpreted as a consequence of the conductivity of the interstitials in the AgBr crystals. According to this interpretation, the influence of the morphology and size of the AgBr grains, and of the addition of stabilizing agent on the conductivity of the AgBr grains can be detected in a simple manner. A continuous transition from surface conductivity towards bulk conductivity of the AgBr grain is observed.
TL;DR: In this article, the calibration factor of a heat flux meter is expressed as a linear function of the thermal conductivity of the medium encompassing the meter, and the slope of the line depends on the geometry and thermal conductivities of the meter.
TL;DR: In this article, a heated probe 2.3 m long and 1 cm in diameter can complete both the gradient and conductivity measurements in 30 min on the ocean floor, and the first two stations show that agreement between the theory of the method and the experimental data is good, and that in situ sediment conductivity at 2.1 x 1O-j cal "C-'cm- s-'is consistent with representative values obtained by steady state laboratory methods.
Abstract: Summary The heated-probe method of measuring sediment conductivity has been successfully adapted to making a multipoint determination in situ over the full gradient interval of a heat-flow measurement. A probe 2.3 m long and 1 cm in diameter can complete both the gradient and conductivity measurements in 30 min on the ocean floor. The first two stations show that agreement between the theory of the method and the experimental data is good, and that in situ sediment conductivity at 2.1 x 1O-j cal "C- ' cm- s- ' is consistent with representative values obtained by steady state laboratory methods.
TL;DR: There have been several previous studies of the dc conductivity of poly(ethylene terephthalate) as mentioned in this paper, and the results indicate the difficulties inherent in this measurement: several authors [1,2] found evidence for ionic conduction through a hopping process; others [3,4] proposed conduction by electrons injected through a barrier.
Abstract: There have been several previous studies of the dc conductivity of poly(ethylene terephthalate). Disagreement among the various authors indicates the difficulties inherent in this measurement: several authors [1,2] found evidence for ionic conduction through a hopping process; others [3,4] proposed conduction by electrons injected through a barrier.
TL;DR: In this paper, the absorption peaks in vitreous As 2 Se 2 were best fit by Gaussian lineshapes and the observed conductivity spectrum satisfactorily accounts for the difference between high and low frequency dielectric constants.
TL;DR: In this article, the electrical conductivity procedure was proposed for the measurement of microbially evolved CO2, previously absorbed in alkali, and the exposure time to atmospheric CO2 was only a few seconds.
Abstract: The advantages of the electrical conductivity procedure proposed for the measurement of microbially evolved CO2, previously absorbed in alkali, are that it is rapid and the exposure time to atmospheric CO2 is only a few seconds. It is as accurate as other accepted techniques. See full-text article at JSTOR