Electrical Properties Of Samples Research Articles

Electrical properties of thin-walled 8 mol% yttria-stabilized zirconia electrolyte tubes prepared by an improved slip casting method

Yttria (8 mol%)-stabilized zirconia electrolyte tubes with thin walls, which are 266 mm in length, 0.4–0.9 mm in thickness, and 96.7% in relative density, were prepared with an improved slip casting method. The microstructure and electrical properties of the samples sintered at different temperatures were studied using SEM and a.c. impedance spectroscopy. The effects of sintered density, grain and grain boundary on the electrical properties of samples were analyzed. The results show that the densification of samples increases gradually with increasing sintering temperatures. The microstructure of samples strongly influences their electrical properties, and with increasing sintered density, the electrical properties of samples are enhanced. The ionic conductivity of grain and grain boundary is improved as the sintering temperatures increase. The grain boundary resistance of samples sintered at 1650°C is higher than that of samples sintered at 1600°C. Better sinterability of samples was obtained at a sintering temperature of 1650°C.

COMBINATORIAL MATERIALS SYNTHESIS AND SCREENING: An Integrated Materials Chip Approach to Discovery and Optimization of Functional Materials

▪ Abstract Combinatorial materials synthesis methods and high throughput evaluation techniques have been developed to accelerate the process of materials discovery and optimization. Analogous to integrated circuit chips, integrated materials chips containing thousands, possibly millions, of different compounds/materials, often in the form of high-quality epitaxial thin film can be fabricated and screened for interesting physical or chemical properties. Microspot X-ray methods, various optical measurement techniques, and a novel evanescent microwave microscope have been used to characterize the structural, optical, magnetic, and electrical properties of samples on materials chips. These techniques are routinely used to discover and optimize luminescent, ferroelectric, dielectric, and magnetic materials.

Properties of CdSe Polycrystalline Thin Films Grown by Chemical Bath

CdSe polycrystalline thin films were grown onto glass substrates by chemical bath deposition at 65°C. Structural, optical, and electrical properties of samples were characterized. The layers grew in the cubic phase as evidenced by X‐ray diffractograms. Using the first derivative of the optical absorption vs. phonon energy curves, two transitions were found, the fundamental at 1.8 eV and a second one at 2.2 eV, respectively. It is worthwhile to mention that the second transition has been reported only for the hexagonal CdSe modification. From the dark conductivity vs. 1/KT behavior on the 100–500 K range, it could be determined an activation energy of 0.3 eV at higher temperatures (>350 K) and a behavior following the variable range hopping model of Mott was satisfied at lower temperature. Electron dispersion spectroscopy measurements indicated stoichiometric CdSe material within the 1 % error bar. © 1999 The Electrochemical Society. All rights reserved.

Combinatorial materials synthesis and high-throughput screening: An integrated materials chip approach to mapping phase diagrams and discovery and optimization of functional materials

Combinatorial materials synthesis methods and high-throughput evaluation techniques have been developed to accelerate the process of materials discovery and optimization and phase-diagram mapping. Analogous to integrated circuit chips, integrated materials chips containing thousands of discrete different compositions or continuous phase diagrams, often in the form of high-quality epitaxial thin films, can be fabricated and screened for interesting properties. Microspot x-ray method, various optical measurement techniques, and a novel evanescent microwave microscope have been used to characterize the structural, optical, magnetic, and electrical properties of samples on the materials chips. These techniques are routinely used to discover/optimize and map phase diagrams of ferroelectric, dielectric, optical, magnetic, and superconducting materials.

Effects of nitrogen on the structure and properties of highly tetrahedral amorphous carbon films

Nitrogen-containing tetrahedral amorphous carbon films (ta-C) have been prepared using a magnetic field filtered plasma stream deposition method. The plasma stream was first formed by sputtering of a graphite target in nitrogen-argon atmospheres. The partial pressure of nitrogen, , was in the range 0-7 Pa at total pressure of deposition Pa. The optical and electrical properties of samples were studied using x-ray photoelectron spectroscopy (XPS), Fourier transform infrared absorption spectroscopy (FTIR), UV-visible optical absorption spectroscopy and measurements of electrical conductivity in the temperature range 300-500 K. The incorporation of small amounts of nitrogen will result in an increase in electrical conductivity, a slight drop of the band gap and an increase in band-tail absorption. These suggest that incorporation of a small amount of nitrogen into ta-C films will induce graphitization of bonding. For samples deposited at Pa, nitrogenation of films is very pronounced. The actual nitrogen content in films in terms of atomic percentage can be as much as 47%. The films have a wide band gap of 4.05 eV and an extremely low electrical conductivity. These suggest that a carbon nitride film is formed. The configurations of N atoms in the ta-C network are identified and discussed.

Non-invasive dielectric measurements with the scanning potential microscope

The scanning potential microscope (SPM) is a new form of scanning microscope, which maps distributions of spatial potential by direct measurement. The SPM may be used to study, non-invasively, the electrical properties of samples through the potential distribution created near the sample in response to an applied electric field. Spatial resolution and sample to SPM spacing are both close to 1 mu m at the present stage of development of the instrument. We present an SPM study of a test sample comprising three dielectric layers with differing relative permittivities: a 35 mu m film of cellulose acetate (CA, epsilon r approximately=5); a 25 mu m film of polyvinylidenefluoride (PVDF, epsilon r approximately=8.4); and a 50 mu m film of polytetrafluoroethylene (PTFE, epsilon r approximately=2-2.1). In the experimental set-up a small, audio-frequency electric displacement was applied through the sample. SPM mapping of the resultant potential distribution close to the sample yielded values of relative permittivity that were within 2% of the material specifications.

SURFACE AND FILM ANALYZER (SFA-A), APPLIED TO CHARACTERIZATION OF POLYMER FILMS

A new device, surface and film analyzer (SFA-A), by which the surface of a sample is ionized and currents flowing in the sample are measured, was applied to organic materials such as polymer films. Grid voltage - current relationships (Vg-I curves) and the influence of temperature on them were studied. Polymer films examined showed different shapes of Vg-I curves from each other according to the electrical properties of samples. Differences in their temperature dependence were also observed. Computer simulation for Vg-I curves reveals close agreement between experimental results and calculated curves.

Synthesis and Physical Properties of Tl-O Monolayer Superconductors: T1Ba1+xLa1−xCuO5and TlBa2Y1−xCaxCu2O7

Abstract Two systems of Tl-based copper oxides with a Tl-O monolayer structure, TlBa2Y1−xCaxCu2O7 (1212 phase) and TlBa1+x La1−xCuO5 (1201 phase), have been synthesized. For x = 0, where formal Cu valences in both systems were estimated to be just +2, samples exhibited semiconductive or insulating behaviors in the resistivity measurement. With increasing x, electrical properties of samples became more metallic and superconductivity appeared. For the 1201 phase, the maximum Tc value was about 40K at around x = 0.2, and sample became a metallic nonsuperconductor for x> =0.4. For the 1212 phase, maximum Tc value was about 90K at around x = 0.8 and metallic nonsuperconductivity was not observed.

Grain boundary structure of YbBa 2Cu 3O 7−x formed by oxidation of metallic precursors

The grain boundaries of superconducting YbBa 2Cu 3O 7− x produced by oxidation of silver-containing metallic precursors under various oxidation conditions have been investigated using mainly a high resolution electron microscopy technique. The grain size of the 1-2-3 superconducting phase is influenced by oxidation temperature and time, and the grains are relatively equiaxed with well developed grain surfaces having a [001] normal. As reported previously, a new phase, YbBa 2Cu 4O x (1-2-4), is often observed at boundaries between grains when one of the grains exhibits a [001] normal at the boundary. The 1-2-4 phase is not observed when both or neither of the grains have a grain boundary normal near [001]. The formation of this phase at grain boundaries is affected by the conditions of oxidation. Whether the 1-2-4 phase is formed or not, grain boundaries whose normal is [001] are terminated with copper oxide basal planes of a 1-2-3 unit cell and there is no amorphous or other grain boundary phases between the two grains. The relationship between these microstructural results and the electrical properties of samples are discussed.

Preparation of hydrogenated amorphous silicon tin alloys

This paper describes a new method to obtain hydrogenated amorphous semiconductor alloys. The method is reactive co-evaporation. Silicon tin hydrogenated alloys are prepared under atomic hydrogen atmosphere. We discuss the influence of various parameters of preparation (hydrogen pressure, tungsten tube temperature, substrate temperature, annealing...) on electrical properties of samples.

Frequency spectrum of the electrical properties of seawater-saturated ocean crust and oceanic island basalts

The frequency spectrum of electrical properties of seawater-saturated oceanic crust and oceanic island basalts has been studied. All samples showed at least two of three possible polarization mechanisms: dielectric, membrane, and electrode. The membrane polarization appears to result from the presence of clay minerals, which frequently line or block pores and cracks in the samples. The dominant conduction mechanism in the samples is pore fluid (seawater) conduction, but the electrical properties of samples containing clay are modified by the clay. The results support the suggestion by Drury that a model of three conduction mechanisms acting approximately in parallel—pore fluid, clay mineral, and metallic mineral conduction—describes the electrical properties of seawater-saturated basalts.

Electrical properties of Pb1−xCdxS epitaxial films

We have measured the resistivity ρ and Hall coefficient RH at 300, 77, and 4.2 K of p-type Pb1−XCdXS epitaxial films as a function of substrate temperature Ts, film thickness d, and composition x. The films were vapor deposited on cleaved (111) BaF2 (111) SrF2 , and (001) NaCl and polished (001) BaF2 substrates. The Hall mobility μH at 77 K of p-type PbS films increased approximately linearly from 1 × 104 to 2 × 104 cm2 V−1 sec−1 as Ts was varied from 400 to 500°C, respectively. Both μH and RH increased with d due to the presence of a strong p-type surface layer on the exposed surface. The x of the films was controlled by the x of the source material and Ts. The mole fraction of CdS could be varied between 0.002 < x < 0.06 by varying T between 513 and 410°C, respectively, and using source material with x = 0.06. The electrical properties of samples grown on freshly cleaved (111) BaF2 and (111) SrF2 were essentially identical even though the lattice constant of SrF2 is a better match to Pb1−XCdXS than BaF2. The RH and μH at 77 K were independent of thickness for low substrate temperatures and were observed to increase with increasing thickness for high substrate temperatures. The μH increased with decreasing temperature and became temperature independent below about 30 K, which is similar to the behavior observed in other lead salt compounds. However, the magnitude of μH was considerable lower throughout the 300 to 4.2 K temperature range than for PbS films. The RH showed little temperature variation, which is typical lead salt behavior.