The electrical conductivity of benzene and its monohalide derivatives in an ultrasonic field

Ultrasonics has found increasing use in instrumentation techniques in recent years as a means of studying the physicochemical properties of materials and articles, and also as a means of accelerating technological processes in various branches of the national economy. At the same time not enough use is made of the possibilities of ultrasonics in many branches of science and technology. These include the study of the effect of ultrasonics on the electrical conductivity of electrolytes, liquid semiconductors, and dielectrics. Available published information on these topics [1 – 5] is scant; the effects observed have been described only qualitatively and need further study.The present paper is devoted to a study of the effect of ultrasonic vibrations (frequency 1.25 Mc, intensity 2 W/cm²) on the electrical conductivity of benzene in an electric field of 5 kV/cm, and on the electrical conductivity of chlorobenzene, bromobenzene, and iodobenzene in a field of 1 kV/cm in the precavitation region. An interpretation of the experimental results is offered.     

Drift mobility and kinetics of transport of excess charge carriers in glassy CdGexAs2

Conclusions We tried to measure transient conductivity response to pulse strongly absorbed excitation (light, accelerated electrons) in sandwich type samples of glassy CdGe _x As₂ compounds. We observed the signal due to transport of free excess carriers. From analysis of experimental results we conclude that in our materials strong trapping effects are present, so the range of excited carriers is very short (10^–4-10^–3 cm) even in the highest electrical fields used (to 10⁴ V. cm^–1). Estimates of upper limit of drift mobility give the values 10^–1- 1 cm² V^–1 sec^–1. We did not succeed in determining the type of carriers which are responsible for the observed effects.     

Charge accumulation by insulators irradiated with electrons

A model, more general than the existing ones, is proposed for the accumulation of charge by plane-parallel insulators irradiated with accelerated electrons. The model takes into account the spatial distribution of the charge injected by the irradiation and the coordinate and time dependence of the bulk electrical conductivity; it is valid for different boundary conditions imposed on the solution of the Poisson equation. The charge density distribution obtained by the light probe method in a sample of a lithium fluoride single crystal irradiated with 2-MeV electrons and current density 5·10^–4 A/m² is described qualitatively by the model.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 49–57, February, 1981.     

Electrophysical properties of heat-treated gallium arsenide

The electrical conductivity, Hall effect, ionization energy, and defect concentration of GaAs samples subjected to various forms of heat treatment were studied. The original material comprised single crystals grown by the Bridgman and Czochralski methods with electron concentrations of 2·10¹⁵–7·10¹⁷ cm^–3. The ionization energy and defect concentration were calculated with an electronic computer. The thermal conversion of GaAs was attributed to traces of copper, lattice defects, and residual impurities. The mobility varied in a complicated manner with the temperature of heat treatment in GaAs samples retaining their original n-type conductivity.Translated from Izvestiya VU Z, Fizika, No. 3, pp. 69–76, March, 1973.     

Electromagnetic-emission diagnostics of dielectric materials under ultrasonic loading

The electromagnetic-emission diagnostic inspection of solid dielectrics subjected to ultrasonic loading created by a pulsed laser beam of nanosecond duration is investigated experimentally. The experimental apparatus and procedure are described. It is shown that the procedure is an effective diagnostic tool for monitoring the electrical state and structure of solid dielectric materials.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 60–65, August, 1993.     

Development of a novel high speed (electron-mobility) epi-n-ZnO thin films by L-MBE for III–V opto-electronic devices

Intrinsic epitaxial zinc oxide (epi-ZnO) thin films were grown by laser-molecular beam epitaxy (L-MBE), i.e., pulsed laser deposition (PLD) technique using Johnson Matthey “specpure”-grade ZnO pellets. The effects of substrate temperatures on ZnO thin film growth, electrical conductivity (σ), mobility (μ) and carrier concentration (n) were studied. As well as the feasibility of developing high quality conducting oxide thin films was also studied simultaneously. The highest conductivity was found for optimized epi-ZnO thin films is σ=0.06×10³ ohm⁻¹ cm⁻¹ (n-type) (which is almost at the edge of semiconductivity range), carrier density n=0.316×10¹⁹ cm⁻³ and mobility μ=98 cm²/V s. The electrical studies further confirmed the semiconductor characteristics of epi-n-ZnO thin films. The relationship between the optical and electrical properties were also graphically enumerated. The electrical parameter values for the films were calculated, graphically enumerated and tabulated. As a novelty point of view, we have concluded that without doping and annealing, we have obtained optimum electrical conductivity with high optical transparency (95%) for as deposited ZnO thin films using PLD. Also, this is the first time that we have applied PLD made ZnO thin films to iso-, hetero-semiconductor–insulator–semiconductor (SIS) type solar cells as transparent conducting oxide (TCO) window layer. We hope that surely these data be helpful either as a scientific or technical basis in the semiconductor processing.     

Electromagnetic effects in the range of separation of chemically combined water from the crystal lattice of muscovite

In order to discover ways of improving the insulating properties of dielectrics and new methods of solving geochronological problems, the electrical and electromagnetic phenomena arising in muscovite samples as a result of the separation of chemically combined water are analyzed. Anomalous changes in electrical conductivity and the intensity of electromagnetic pulses in the radiofrequency range suggest the separation of a quartz phase in muscovite subjected to the action of thermal and electric fields.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 20–27, January, 1977.     

Electrical conductivity improvement of strontium titanate doped lead vanadate glasses by nanocrystallization

The structural and electrical conductivity (σ) of annealed SrTiO₃–PbO₂–V₂O₅ glasses were studied. The annealing of initially glass samples leads to formation of nanocrystalline grains embedded in the glassy matrix. XRD patterns of the glass–ceramic samples show that nanocrystals were embedded in the glassy matrix with an average grain size of 32 nm. The glass–ceramic nanocrystals obtained by annealing at temperatures close to the crystallization temperature T_c exhibit enhancement of electrical conductivity up to four orders of magnitude than initially glasses. The enhancement of the electrical conductivity due to annealing was attributed to two interdependent factors: (i) an increase of concentration of V⁴⁺–V⁵⁺ pairs; and (ii) formation of defective, well-conducting regions along the glass–crystallites interfaces. From the conductivity temperature relation, it was found that small polaron hopping model was applicable at temperature above θ_D/2 (θ_D, the Debye temperature). The electrical conduction at T >θ_D/2 was due to non-adiabatic small polaron hopping (SPH) of electrons between vanadium ions. The parameters obtained from the fits of the experimental data to this model appear reasonable and are consistent with glass composition.     

Power factor enhancement in Pr-substituted alloys prepared by high-pressure sintering

Bi₈₅Sb_15−xPr_x (x=0,1,2,3) alloys with partial substitution of Pr for Sb were synthesized by mechanical alloying followed by high-pressure sintering. The crystal structure was characterized by X-ray diffraction. The electrical conductivity and Seebeck coefficient were measured in the temperature range of 80–300 K. The results show that the electrical conductivity and Seebeck coefficient of Pr-substituted samples are both larger than those of the reference sample, Bi₈₅Sb₁₅, in the whole measurement temperature range. The power factor of Bi₈₅Sb₁₃Pr₂ reaches a maximum value of 3.83×10⁻³ W K⁻² m⁻¹ at 235 K, which is about four times larger than that of the reference sample, Bi₈₅Sb₁₅, at the same temperature.     

Non-pixeled amorphous silicon-based image sensors

Large area hydrogenated amorphous silicon p–i–n structures with low conductivity doped layers were proposed as single element monochrome image sensors. The investigation of the sensor output under different scanner wavelengths and varying electrical bias reveals that the response can be tuned to a certain wavelength, thus enabling color separation. The measurement technique is described in detail and two methods for color separation are proposed. The sensor output characteristics are evaluated under different bias voltages and wavelengths. The color separation mechanism can be explained by the variation of the band bending with light wavelength.The operation of the sensor is exemplified under illumination with a polychromatic image and using one of the proposed detection methods.     

Synthesis and characterizations of AgSCN nanospheres using AgCl as the precursor

Nanospheres of AgSCN with an average radius of 30–80 nm have been prepared by a simple reaction between AgCl suspension and KSCN in the presence of gelatin. Gelatin played a decisive role as an inhibitor of the direct attack of SCN⁻ ions to AgCl surfaces and coagulation of the growing AgSCN in producing the spherical AgSCN nanoparticles. The products were characterized by X-ray powder diffraction, transmission electron microscopy and X-ray photoelectron spectra techniques. The electrical conductivity of thin films of as-prepared AgSCN nanoparticles and polyethylene oxide (PEO) at room temperature was measured. The maximum value of electrical conductivity of as-prepared AgSCN–PEO was 1.53 × 10⁻⁵ S cm⁻¹.     

Electrical conductivity of Ag/Na ion-exchanged titanosilicate glasses

The Ag₂O–TiO₂–SiO₂ glasses were prepared by Ag⁺/Na⁺ ion-exchange method from Na₂O–TiO₂–SiO₂ glasses at 380–450 °C below their glass transition temperatures (T_g), and their electrical conductivities were investigated as functions of TiO₂ content and the ion-exchange ratio (Ag/(Ag+Na)). In a series of glasses 20R₂O·xTiO₂·(80−x)SiO₂ with x=10, 20, 30 and 40 in mol%, the electrical conductivities at 200 °C of the fully ion-exchanged glasses of R=Ag were in the order of 10⁻⁵ or 10⁻⁴ S cm⁻¹ and were 1 or 2 orders of magnitude higher than those of the initial glasses of R=Na. The glass of x=30 exhibited the highest increase of conductivity from 3.8×10⁻⁷ to 1.3×10⁻⁴ S cm⁻¹ at 200 °C by Ag⁺/Na⁺ ion exchange among them. When the ion-exchange ratio was changed in 20R₂O·30TiO₂·50SiO₂ system, the electrical conductivity at 200 °C exhibited a minimum value of 7.6×10⁻⁸ S cm⁻¹ around Ag/(Ag+Na)=0.3 and increased steeply in the region of Ag/(Ag+Na)=0.5–1.0. When the ion-exchange temperature was changed from 450 to 400 °C, the conductivity of the ion-exchanged glass of x=30 decreased. The infrared spectroscopy measurement revealed that the ion-exchange temperature of 450 °C induced a structural change in the glass of x=30. The T_g of the fully ion-exchanged glass of x=30 was 498 °C. It was suggested that the incorporated silver ions changed the average coordination number of titanium ions to form higher ion-conducting pathway and resulted in high conductivity in the titanosilicate glasses.     

The effect of measurement temperature on the thermo-emf and electrical resistivity of some homogeneously graphitized carbonaceous materials

This paper gives the results of measuring the temperature dependence of the thermo-emf and electrical conductivity of petroleum cokes which had undergone heat treatment at 1700–2700 ° K. The temperature dependence was studied in the range 300–1100 ° K. The experimental data are discussed in the light of existing ideas on the theory of graphitization and of the band structure of carbonaceous material.The authors wish to express their gratitude to Professor N. F. Kunin for his constant interest in their work.     

Optical and electrical properties of optimized thin gold films as top layer of MIS solar cells

The optical spectral response between 340–860 nm and electrical conductivity measurements were made on thermally evaporated gold films in the thickness range 50–130 Å in order to identify optimal properties for their use as the top layer of MIS solar cells. Films of lower evaporation rate and thickness range 70–100 Å were found to have high transmittance and low reflectance, which is desirable for the above purpose. Films thinner than 70 Å had poor electrical conductivity and thicker than 100 Å had poor solar transmittance, hence were rejected. Improved transmittance and conductivity were obtained upon annealing the film at 250°C for about two hours.     

Mechanical and electrical characteristics of silver stabilizer layer prepared by using nano silver paste for coated conductor

Mechanical and electrical properties of silver stabilizer layer of coated conductor, which was prepared using nano silver paste as starting materials, have been investigated. Nano silver paste was coated on YBCO (Y₁Ba₂Cu₃O_7−δ) film by a dip coating method with a speed of 25 mm/min. Coated film was dried in air and heat treated at 400–700 °C in a flowing oxygen atmosphere. Adhesion strength between YBCO and silver layer was measured by Tape test (ASTM D 3359). The hardness and electrical conductivity of the sample were measured by pencil hardness test (ASTM D 3363). Surface and volume resistance were measured by using LORESTA-GP (MITSUBISHI). The sample heat treated at 500 °C showed poor adhesiveness of 1B but it is clearly enhanced to 5B when samples were heat treated at higher than 600 °C. The silver layer heat treated at 700 °C showed a high hardness value of higher than 9H and a volume resistance of 1.417 × 10⁻⁷ Ω mm at room temperature. SEM observations showed that a dense silver layer was formed with a thickness of about 2 μm. Dip coated silver layer prepared by using nano silver paste showed superior electrical and mechanical characteristics which is comparable to those that sputter deposited Ag layer.     

Electrical conductivity and photoconductivity of single crystals of lithium hydride

Nonactivated LiH crystals and crystals of LiH with Mg, In, Tl, Sn, Sb, and Bi impurities are investigated. Photoconductivity is found in luminescent crystals. The temperature dependence of the electrical conductivity and photoconductivity in the temperature range of 100–570 ° K is measured. Volt-ampere characteristics of the dark current and photocurrent in fields up to 10⁴ V/cm at various temperatures are obtained. Data is presented on the inertia of the photocurrent and its dependence on the intensity of the exciting light. Conclusions are drawn concerning some connection of LiH photoconductivity with the type of activating impurity, the absence of a connection with the brightness of the luminescence, and the specific role of photoconductivity in color centers.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, No. 10, pp. 94–98, October, 1971.     

Paramagnetic defects in BaTiO3 and their role in light-induced charge transport — Optical studies

On the basis of a previous identification of paramagnetic defects in nominally undoped as grown BaTiO₃ single crystals, we have investigated the changes of the concentrations of these centers and their optical absorptions under illumination with light of varying wavelengths. The most pronounced charge transfers occur by hole ionization of Fe⁴⁺ and — to a lesser extent — of Cr⁵⁺ and Cr⁴⁺. At low temperatures the created holes are trapped in the form of O^–-ions next to Al³⁺ or unknown acceptor defects. Corresponding Fe⁴⁺ and O^– absorptions have been identified.     

Study op electrical conductivity op some chalkogenide glasses under hydrostatic pressure up to 1000 MPa

The study of electrical properties of amorphous materials under high pressure can contribute to understanding of processes in these materials and helps to build the theory of amorphous materials. Properties of these materials under high pressure are studied for instance in papers /1–6/. The change of electrical conductivity is usually ascribed to the change of activation energy due to hydrostatic pressure.     

Electrical conductivity and thermoelectric power of AgInSe2 in the solid and liquid states

The electrical conductivity and thermoelectric power of AgInSe₂ have been investigated as a function of temperature from 420°C to 950°C. Experimental data are analyzed in terms of a model developed for the density of states and electrical transport in solid amorphous semiconductors [1]. The activation energy calculated from electrical conductivity data is found to be 0.06 eV for the solid and 0.37 eV for the liquid phase. Moreover, the coefficient of the linear decrease of the energy gap with temperature was found to be 1.96×10^–4 eV/K.     

Preparation and basic physical properties of BiTeI single crystals

A modified Bridgman method is described, which makes it possible to prepare homogeneous BiTeI crystals using excess iodine. At room temperature the values of the electrical conductivity of the crystals range around 2000 ^–1 cm^–1, the Hall constant value about 0·09 cm^–3 coul^–1, the Seebeck coefficient about 50 V K^–1. In connection with the assumption of super-stoichiometric iodine content we expect there exist point defects in the crystals, where Te atoms are replaced with I atoms, which gives rise to electric conductivity. On the basis of the temperature dependence of the electron mobility one can suppose a mixed mechanism of the scattering of the free carriers by the acoustic branch of lattice vibrations and by ionized impurities.