Conductive Intermediate Layer Research Articles

Preparation of Diamond Mold Using Electron Beam Lithography for Application to Nanoimprint Lithography

Diamond molds were fabricated by two types of fabrication processes, both of which use a conductive intermediate layer between the diamond surface and polymethylmethacrylate (PMMA) resist to prevent surface charge-up. Using a PtPd intermediate layer, electron beam lithography and ion beam etching, a denting line pattern of 600 nm width and 70 nm depth was fabricated. Using a carbon intermediate layer, electron beam lithography, PtPd lift-off and oxygen ion beam etching, a convex line pattern of 600 nm width and 110 nm height was fabricated. These diamond molds were pressed into PMMA on a silicon substrate that was heated to a temperature of 150°C and kept at a pressure of 23.5 MPa until the temperature dropped below 90°C, and then the diamond mold was released from the PMMA. The convex line pattern of 600 nm width and 150 nm height was imprinted using a denting diamond mold. The denting pattern of 1100 nm width and 180 nm height was imprinted using a convex diamond mold. PMMA patterns were transferred well over the imprinted area by the diamond molds.

Effects of intermediate semiconductor layers on carrier transport mechanisms through p-ZnSe/metals interfaces

The effects of formation of intermediate semiconductor layers at p-ZnSe/metals interfaces on carrier transport mechanisms were studied by comparing contacts prepared by the deposition and annealing (DA) technique or the molecular beam epitaxy (MBE) technique. Current density vs voltage (J-V) curves of the MBE contact with a p-ZnSe/p-ZnTe superlattice intermediate layer showed ohmic behavior. However, J-V curves of the DA contact with a ZnTe intermediate layer showed rectifying behavior. The difference of the electrical properties between these two contacts was due to existence of a highly resistive intermediate layer with highly dense defects in the DA contact and a low resistance p-type conductive intermediate layer with relatively small densities of crystalline defects in the MBE contacts. From the present results, it was concluded that formation of the highly resistive semiconductor layer with dense crystalline defects prevented the DA contact to transit from non-ohmic J-V behavior to ohmic.

Interpretation of slingram conductivity mapping in near‐surface geophysics: using a single parameter fitting with 1D model1

AbstractElectrical conductivity mapping is a prerequisite tool for hydrogeological or environmental studies. Its interpretation still remains qualitative but advantages can be expected from a quantitative approach. However a full 3D interpretation is too laborious a task in comparison with the limited cost and time which are involved in the majority of such field studies. It is then of value to define the situations where lateral variations are sufficiently smooth for a 1D model to describe correctly the underlying features.For slingram conductivity measurements, criteria allowing an approximate 1D inversion are defined: these mainly consist of a limited rate of variation over three times the intercoil spacing.In geological contexts where the weathering has generated a conductive intermediate layer between the underlying sound rock and the soil, this processing can be applied to determine the thickness of the conductive layer from the apparent resistivity map when the other geoelectrical parameters are known. The examples presented illustrate this application.

The role of the silver intermediate layer in the YBa 2Cu 3O 7−x/Ag/ In 2O 3/Si system

Superconducting YBa 2Cu 3O 7− x (YBCO) thin films were deposited on Si(111) substrates with a conductive intermediate layer of Ag In 2O 3 . In 2O 3 was prepared by the d.c. magnetron method and a silver thin film was evaporated on the In 2O 3/Si(111). The YBCO thin films were deposited by d.c. magnetron sputtering. The conductive In 2O 3 thin film was used to minimize the interdiffusion between silicon and the YBCO superconducting material. The silver thin film improves the zero-resistance temperature, transition temperature width, and the critical current density of the superconducting YBCO film in the YBCO/In 2O 3/Si system. Films of YBCO on the Ag/In 2O 3/Si substrate have zero resistance at 85 K and a critical current density of 2.0 x 10 3 A cm −2 at 77 K. The XRD spectrum indicates that the superconducting thin films have a preferential c axis oriented structure. Auger electron spectroscopy depth profiling was used to analyse the interfaces.

Progress in the design of mechanically attached, conductively cooled low- Z armour tiles for the NET integrated first wall

For the NET device complete or extensive coverage of the first wall with a low- Z armour is envisaged. This armour may comprise a general protection, ∼ 90% total first-wall surface, of low-temperature conductively cooled tiles, complemented by a local protection of radiatively cooled tiles in regions where near peak fluxes are incident. A low-temperature (∼ 1000°C) carbon-based armour, cooled via conduction to the reference NET integrated first wall, has been developed using currently available materials. The amour comprises a small square tile fabricated in high-conductivity 3-D or random-fibre carbon fibre reinforced carbon composite attached to the steel first wall via a stainless-steel/refractory metal stud assembly. Attachment forces are maintained within acceptable limits, particularly during baking, through material selection and component geometry. To ensure effective heat transfer throughout the duty cycle an intermediate conductive layer of a highly compliant material is foreseen. The scope of the paper covers the design of the armour assembly for proof of principle testing with the NET first-wall test section, TS1, and reports the results of supporting thermomechanical analyses.

Mid cretaceous contact seen below seymour island and followed off shore by the magnetotelluric method along the ne coast of the Antarctic peninsula

Magnetotelluric soundings were made on two off-shore islands and on the Larsen ice shelf. Below Seymour Island a thick sedimentary accumulation (6.7 km) is found. The mid Cretaceous contact is seen at a depth of 4.7 km. The first intermediate conductive layer appears at 65 km with a thickness of 20 km and a 10 ohm m resistivity. Two hundred km farther to the SW, from Robertson Island to Cape Fairweather, an anticline of the basement is possible; the depth ranges from 0.9 km at the top, to 2.3 and 3.6 km at the edges. The mid Cretaceous contact is followed off shore. The intermediate conductive layer begins at about 30 km depth on an average.

Detectability of Intermediate conductive and resistive layers by time‐domain electromagnetic sounding

An analysis in the time domain has been made of the detectability of an intermediate layer in a three‐layer earth model by the horizontal coplanar loops (system I) and loop‐wire element (system V) electromagnetic (EM) sounding systems for a train of half‐sinusoidal and square waveforms of alternating polarity. The studies involve conversion into the time domain by a Fourier series summation of the matched complex mutual coupling ratios, computed by the digital linear filter method, of the layered‐earth models. The three‐layer earth models considered here have the following resistivity distribution: [Formula: see text], [Formula: see text] for the conductive case, and [Formula: see text], [Formula: see text] for the resistive case (subscripts 1, 2, and 3 represent the first, second, and third layer in the three‐layer sequence; ρ is the resistivity). The intermediate‐layer thickness varies over a wide range. The responses of the three‐layer earth models have been compared with that of a homogeneous earth with the resistivity of the top layer in the three‐layer sequence. The measurement error is assumed to be of the order of 3 percent, and an rms difference of 10 percent between the responses for the three‐layer and the homogenous earth is defined as the detectability level. On the basis of this definition, it is observed that the horizontal coplanar loops system (system I) is better than the loop‐wire element system (system V) in detecting the thin intermediate layer, which may be either conductive or resistive. For a transmitter‐receiver separation (R) of 1000 m by square‐pulse excitation, a conductive intermediate layer as thin as 1/14 of the top layer can be detected by system I and as thin as 1/6 by system V. For the resistive intermediate layer, the corresponding thickness ratios are 0.6 for system I and 1.25 for system V. The detectability is lower in the case of half‐sinusoidal pulse excitation. Instead of normalizing the mutual coupling of the layered earth to the free‐space coupling, the detectability is enhanced markedly if the normalization is done to the coupling over a homogeneous ground. For system V, it is observed that an intermediate layer as thin as 1/100 in the conductive case and 1/4 in the resistive case of the top layer can be detected easily by this approach. Some direct comparisons between the time‐domain and the frequency‐domain results also are given.

TIME‐DOMAIN ELECTROMAGNETIC SOUNDING—COMPUTATION OF MULTI‐LAYER RESPONSE AND THE PROBLEM OF EQUIVALENCE IN INTERPRETATION*

AbstractComputations of the time‐domain electromagnetic response of a multi‐layered earth have been carried out for different source‐receiver coil systems. The primary excitation is a train of half‐sinusoidal waveforms of alternating polarity. The conversion into the time‐domain involves Fourier series summation of the matched complex mutual coupling ratios of the layered earth models computed by a digital linear filter method. As an example, the response of a perpendicular coil system on the ground surface for two source‐receiver separations has been presented for a five‐layer earth model. This has been compared with the responses of homogeneous, two‐layer, three‐layer, and four‐layer models.Next, the investigations have been extended to study the problems of equivalence of three‐layer models, the intermediate layer of which is either conductive or resistive. For an intermediate conductive layer (H‐type), the studies show that in the early portion of the signal the interpretation of a true three‐layer earth is possible to some extent, whereas the ambiguity due to equivalence persists in the late samples. On the other hand, for an intermediate resistive layer (K‐type), the three‐layer earth and its equivalent model cannot be distinguished from each other over the entire sampling period.On the basis of a computational approach, equivalence has been empirically established as √h/ρ=constant for H‐type earth‐sections, and as h2ρ=constant for K‐type earth sections, where h and ρ are respectively the thickness and resistivity of the intermediate layer.

Ion selective electrodes

An ion-selective electrode (10) including a water-impermeable, non-conductive substrate (12); an electrically conductive layer including a metal/metal salt mixture (14) supported on a surface of the substrate; a hydrophobic, conductive intermediate layer (16) in contact with the metal/metal salt layer and including a salt having suitable ionic mobility such that an electrode potential is rapidly established; a layer (18) including an ion-specific ligand in contact with the intermediate layer; and a water-impermeable barrier layer (20) which overlays the layer including the ion-specific ligand such that a portion of this layer is uncovered, and a method for preparing same, is described. The present ion-selective electrode permits rapid, reproducible measurements of ion concentrations to be made without requiring electrode calibration and in the absence of liquid electrolytes.

RESISTIVITY ANALYSIS FOR MODELS OF A SPHERE IN A HALF‐SPACE WITH BURIED CURRENT SOURCES*

AbstractBoundary‐value problems in steady‐state current flow were solved numerically in bispherical coordinates for a sphere of arbitrary conductivity in a half‐space. Solutions for the potential on the surface of the half‐space were examined for the cases where both current sources were on the surface, one source on the surface and the second between the surface and the sphere, and one source on the surface and the other in the sphere. Results show a great similarity with the layered case when the buried electrode is placed between the surface and the conducting region. Such a buried electrode configuration makes it possible to obtain an accurate measurement of the depth to the conductor in both cases. A model with the current electrode placed in a conductive sphere is compared with a three‐layered model with the source in a conductive intermediate layer, and results indicate that the lateral extent of a finite anomalous zone can be estimated using these limiting curves. The validity of these theoretical calculations for buried spheres was confirmed experimentally by tests conducted on an analog model.