Energy-dispersive x-ray mapping of grain boundaries in high-Tc superconductors

1993 ◽  
Vol 51 ◽  
pp. 442-443
Author(s):  
J.C. Barry ◽  
G.J. Auchterlonie
Keyword(s):  
Critical Temperature ◽  
Grain Boundaries ◽  
Large Scale ◽  
Current Flow ◽  
Power Transmission ◽  
Electrical Current ◽  
Oxide Superconductors ◽  
High Tc ◽  
Order Of Magnitude ◽  
Better Than

Superconductors are materials which carry electrical current without resistive loss below a certain critical temperature (Tc). There are many potential uses for materials that are superconducting, but until recently the Tc's of known materials were too low to be useful in large-scale applications such as power transmission. However, with the discovery of high Tc oxide superconductors, the feasibility of such projects are now being considered. The problem with the oxide superconductors is not that their critical temperature is too low (the Tc's of the oxides are almost an order of magnitude better than the metal superconductors), but rather that in bulk form their current carrying capacity (Jc) is too low. It is known that the bulk Jc is determined by intergranular conductivity. Low values for Jc may occur because of: (a) a change of stoichiometry at the grain boundaries, or (b) because of misorientation of adjacent grains. High Jc's can be achieved in thin films by texturing the material so that there are few grain boundaries across the direction of current flow but many grain boundaries perpendicular to the current flow.

Effect of Current Direction on the Reliability of Different Capped Cu Interconnects

2005 ◽  
Vol 863 ◽  
Author(s):  
C. L. Gan ◽  
C. Y. Lee ◽  
C. K. Cheng ◽  
J. Gambino
Keyword(s):  
Failure Analysis ◽  
Current Flow ◽  
Void Nucleation ◽  
Electrical Current ◽  
Nucleation Site ◽  
Time To Failure ◽  
Current Direction ◽  
Electron Current ◽  
Electrical Current Flow ◽  
Better Than

AbstractThe reliability of Cu M1-V1-M2-V2-M3 interconnects with SiN and CoWP cap layers was investigated. Similar to previously reported results, the reliability of CoWP capped structures is much better than identical SiN capped structures. However, it was also observed that the reliability of CoWP capped interconnects was independent of the direction of electrical current flow. This phenomenon is different from what was observed for SiN capped structures, where M2 lines with electron current flow in the upstream configuration (“via-below”) have about three times larger median-time-to-failure than identical lines in the downstream configuration (“viaabove”). This is because the Cu/SiN interface is the preferential void nucleation site and provides the fastest diffusion pathway in such an architecture. Failure analysis has shown that fatal partially-spanned voids usually had formed directly below the via for “via-above” configuration, and fully-spanned voids occurred in the lines above the vias for “via-below” configuration.On the other hand, failure analysis for CoWP-coated Cu structures showed that partiallyspanned voids below the via do not cause fatal failures in the downstream configuration. This is because the CoWP layer is conducting, and thus able to shunt current around the void. As a result, a large fully-spanning void is required to cause a failure, just like the upstream configuration. Thus the lifetime of an interconnect with a conducting cap layer is independent of whether the current is flowing upstream or downstream.

Grain Boundaries and Jc in High-Tc Oxide Superconductors

JOM ◽  
1989 ◽  
Vol 41 (1) ◽  
pp. 14-17 ◽  
Author(s):  
D. M. Kroeger
Keyword(s):  
Grain Boundaries ◽  
Oxide Superconductors ◽  
High Tc

MINIMAL ANOMALOUS OCCUPANCY IN HIGH-Tc SUPERCONDUCTIVITY

1993 ◽  
Vol 07 (24n25) ◽  
pp. 1601-1609 ◽  
Author(s):  
R.M. MÉNDEZ-MORENO ◽  
M. MORENO ◽  
S. OROZCO ◽  
M.A. ORTÍZ
Keyword(s):  
Critical Temperature ◽  
Copper Oxide ◽  
Cuprate Superconductors ◽  
Normal Limit ◽  
Good Description ◽  
Energy Scale ◽  
Oxide Superconductors ◽  
High Tc ◽  
Copper Oxide Superconductors ◽  
Fermion Gas

A study of a minimal anomalous occupancy is carried out when a small gap occurs near the Fermi surface. A limit which tends softly to the normal occupancy can be introduced. This framework is applied to a quasi-bidimensional fermion gas which can mimick the copper oxide planes in cuprate superconductors. The energy scale implied by this minimally anomalous occupancy (the soft normal limit) for high-T c cuprate superconductors is of the order of the Debye energy. Yet this anomalous occupancy framework overcomes the phonon barrier and a good description for the critical temperature of a representative set of high-T c copper oxide superconductors is obtained.

Study on the Sintering and Mg Composition Effect on MgB2 Superconducting Bulks and Wires Synthesized by Powder-in-Sealed-Tube Method

2021 ◽  
Vol 1166 ◽  
pp. 1-12
Author(s):  
Md Rauf Ul Karim Khan ◽  
Agung Imaduddin ◽  
Heri Nugraha ◽  
Reiji Hattori ◽  
Andika Widya Pramono
Keyword(s):  
Critical Temperature ◽  
Large Scale ◽  
Stoichiometric Ratio ◽  
Composition Effect ◽  
High Tc ◽  
X Ray ◽  
Superconducting Wires ◽  
Superconducting Wire ◽  
Coherence Lengths ◽  
Sintered Temperature

Numerous research efforts aimed at the MgB2 (Magnesium diboride) as a superconducting material due to its higher critical temperature than Nb-based superconductors such as NbTi, Nb3Sn. Nowadays MgB2 is becoming more popular as the candidate to be applied on medical devices and large-scale applications because of its full coherence lengths, improved critical current density and fields, and simple crystal structure. In this study, we fabricated the 4 mm MgB2 superconducting wires by mixing stoichiometric mole ratio of Mg: B with 1.0:2.0 and 1.1:2.0 through the Powder-In-Sealed-Tube (PIST) method to optimize high critical temperature (TC) than the conventional MgB2 bulk and wire. Furthermore, we decreased the diameter of 4 mm to 1.8 mm wire and analyze the effect of critical temperature. The specimens were sintered at a different temperature to investigate the sintering effect of MgB2 superconducting wire. The resistivity versus temperature relationship, surface morphology, and crystal phase was characterized using Cryogenic system, SEM (Scanning Electron Microscopy), and XRD (X-ray Diffractometer), respectively. We optimized the high Tc,onset for the bulk and 4 mm wire compared to other studies that are 42.1K and 40.3K respectively at 800°C sintered temperature. Finally, the results suggest that the stoichiometric ratio of MgB2 exhibited excellent feasibility to prepare conventional MgB2 superconducting wire.

Finding the Right Problems: Some HREM Applications to Interfaces

1984 ◽  
Vol 42 ◽  
pp. 376-379
Author(s):  
D. Cherns
Keyword(s):  
Grain Boundaries ◽  
High Resolution Electron Microscopy ◽  
Boundary Structure ◽  
Atomic Structures ◽  
Grain Boundary Structure ◽  
Resolution Electron ◽  
Point To Point ◽  
The Right ◽  
New Generation ◽  
Better Than

The use of high resolution electron microscopy (HREM) to determine the atomic structure of grain boundaries and interfaces is a topic of great current interest. Grain boundary structure has been considered for many years as central to an understanding of the mechanical and transport properties of materials. Some more recent attention has focussed on the atomic structures of metalsemiconductor interfaces which are believed to control electrical properties of contacts. The atomic structures of interfaces in semiconductor or metal multilayers is an area of growing interest for understanding the unusual electrical or mechanical properties which these new materials possess. However, although the point-to-point resolutions of currently available HREMs, ∼2-3Å, appear sufficient to solve many of these problems, few atomic models of grain boundaries and interfaces have been derived. Moreover, with a new generation of 300-400kV instruments promising resolutions in the 1.6-2.0 Å range, and resolutions better than 1.5Å expected from specialist instruments, it is an appropriate time to consider the usefulness of HREM for interface studies.

Atomic resolution AEM (ARAEM) of oxide superconductors

1992 ◽  
Vol 50 (1) ◽  
pp. 74-75
Author(s):  
Vinayak P. Dravid ◽  
H. Zhang ◽  
L.D. Marks ◽  
J.P. Zhang
Keyword(s):  
Electron Microscope ◽  
Field Emission ◽  
Atomic Resolution ◽  
Oxide Superconductors ◽  
Electron Holography ◽  
Analytical Electron ◽  
Analytical Electron Microscope ◽  
Point To Point ◽  
Single Instrument ◽  
Better Than

A 200 kV cold field emission gun atomic resolution analytical electron microscope (ARAEM, Hitachi HF-2000) has been recently installed at Northwestern. The ARAEM offers an unprecedented combination of atomic structure imaging of better than 0.20 nm nominal point-to-point resolution and about 0.10 nm line resolution, alongwith nanoscale analytical capabilities and electron holography in one single instrument. The ARAEM has been fully functional/operational and this paper presents some illustrative examples of application of ARAEM techniques to oxide superconductors. Additional results will be presented at the meeting.

High Resolution Electron Microscopy of internal interfaces in layered materials

1990 ◽  
Vol 48 (4) ◽  
pp. 320-321
Author(s):  
Yoichi Ishida ◽  
Hideki Ichinose ◽  
Yutaka Takahashi ◽  
Jin-yeh Wang
Keyword(s):  
Grain Boundaries ◽  
Mirror Symmetry ◽  
Functional Materials ◽  
High Resolution Electron Microscopy ◽  
Layered Materials ◽  
Plane Boundary ◽  
Chemical Information ◽  
Layer Plane ◽  
High Tc ◽  
Cubic Metals

Layered materials draw attention in recent years in response to the world-wide drive to discover new functional materials. High-Tc superconducting oxide is one example. Internal interfaces in such layered materials differ significantly from those of cubic metals. They are often parallel to the layer of the neighboring crystals in sintered samples(layer plane boundary), while periodically ordered interfaces with the two neighboring crystals in mirror symmetry to each other are relatively rare. Consequently, the atomistic features of the interface differ significantly from those of cubic metals. In this paper grain boundaries in sintered high-Tc superconducting oxides, joined interfaces between engineering ceramics with metals, and polytype interfaces in vapor-deposited bicrystal are examined to collect atomic information of the interfaces in layered materials. The analysis proved that they are not neccessarily more complicated than that of simple grain boundaries in cubic metals. The interfaces are majorly layer plane type which is parallel to the compound layer. Secondly, chemical information is often available, which helps the interpretation of the interface atomic structure.

PENGEMBANGAN MEDIA BIG BOOK UNTUK MENINGKATKAN HASIL BELAJAR PECAHAN SENILAI SISWA SD

2018 ◽  
Vol 16 (1) ◽  
pp. 67-76
Author(s):  
Disyacitta Neolia Firdana ◽  
Trimurtini Trimurtini
Keyword(s):  
Learning Outcomes ◽  
Large Scale ◽  
Fourth Grade ◽  
Learning Activities ◽  
Equivalent Fractions ◽  
Fourth Grade Students ◽  
Teacher Needs ◽  
The Media ◽  
Test Result ◽  
Better Than

This research aimed to determine the properness and effectiveness of the big book media on learning equivalent fractions of fourth grade students. The method of research is Research and Development  (R&D). This study was conducted in fourth grade of SDN Karanganyar 02 Kota Semarang. Data sources from media validation, material validation, learning outcomes, and teacher and students responses on developed media. Pre-experimental research design with one group pretest-posttest design. Big book developed consist of equivalent fractions material, students learning activities sheets with rectangle and circle shape pictures, and questions about equivalent fractions. Big book was developed based on students and teacher needs. This big book fulfill the media validity of 3,75 with very good criteria and scored 3 by material experts with good criteria. In large-scale trial, the result of students posttest have learning outcomes completness 82,14%. The result of N-gain calculation with result 0,55 indicates the criterion “medium”. The t-test result 9,6320 > 2,0484 which means the average of posttest outcomes is better than the average of pretest outcomes. Based on that data, this study has produced big book media which proper and effective as a media of learning equivalent fractions of fourth grade elementary school.

scholarly journals Nebula: ultra-efficient mapping-free structural variant genotyper

2021 ◽  
Author(s):  
Parsoa Khorsand ◽  
Fereydoun Hormozdiari
Keyword(s):  
Large Scale ◽  
Structural Variants ◽  
Sequencing Technologies ◽  
Generic Framework ◽  
Common Genetic Variants ◽  
Order Of Magnitude ◽  
Complex Events ◽  
Comparable Accuracy ◽  
Using Data ◽  
Computational Resources

Abstract Large scale catalogs of common genetic variants (including indels and structural variants) are being created using data from second and third generation whole-genome sequencing technologies. However, the genotyping of these variants in newly sequenced samples is a nontrivial task that requires extensive computational resources. Furthermore, current approaches are mostly limited to only specific types of variants and are generally prone to various errors and ambiguities when genotyping complex events. We are proposing an ultra-efficient approach for genotyping any type of structural variation that is not limited by the shortcomings and complexities of current mapping-based approaches. Our method Nebula utilizes the changes in the count of k-mers to predict the genotype of structural variants. We have shown that not only Nebula is an order of magnitude faster than mapping based approaches for genotyping structural variants, but also has comparable accuracy to state-of-the-art approaches. Furthermore, Nebula is a generic framework not limited to any specific type of event. Nebula is publicly available at https://github.com/Parsoa/Nebula.

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