scholarly journals Fabrication of large-area uniform carbon nanotube foams as near-critical-density targets for laser–plasma experiments

2021 ◽  
Vol 9 ◽  
Author(s):  
Pengjie Wang ◽  
Guijun Qi ◽  
Zhuo Pan ◽  
Defeng Kong ◽  
Yinren Shou ◽  
...  
Keyword(s):  
Carbon Nanotube ◽  
Critical Density ◽  
Chemical Vapor ◽  
High Energy ◽  
Large Area ◽  
Characterization Methods ◽  
Synthesis Parameters ◽  
High Energy Ions ◽  
Target Characterization ◽  
First Time

Abstract Carbon nanotube foams (CNFs) have been successfully used as near-critical-density targets in the laser-driven acceleration of high-energy ions and electrons. Here we report the recent advances in the fabrication technique of such targets. With the further developed floating catalyst chemical vapor deposition (FCCVD) method, large-area ( $>25\kern0.5em {\mathrm{cm}}^2$ ) and highly uniform CNFs are successfully deposited on nanometer-thin metal or plastic foils as double-layer targets. The density and thickness of the CNF can be controlled in the range of $1{-}13\kern0.5em \mathrm{mg}/{\mathrm{cm}}^3$ and $10{-}200\kern0.5em \mu \mathrm{m}$ , respectively, by varying the synthesis parameters. The dependence of the target properties on the synthesis parameters and the details of the target characterization methods are presented for the first time.

Block Copolymer Assisted Fabrication of Graphene/Carbon Nanotube Hybrid Architectures and Their Application in Supercapacitors

2012 ◽  
Vol 1440 ◽  
Author(s):  
Aaron S. George ◽  
Maziar Ghazinejad ◽  
Wei Wang ◽  
Isaac Ruiz ◽  
Mihrimah Ozkan ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Chemical Vapor Deposition ◽  
Carbon Nanotube ◽  
Energy Storage ◽  
Vapor Deposition ◽  
High Surface ◽  
High Surface Area ◽  
Chemical Vapor ◽  
High Energy ◽  
Large Area

AbstractSustainable energy is currently limited by the ability of materials to store energy and deliver it on demand. Allotropes of carbon are attractive for their potential for use in energy storage due to low weight, high chemical stability and low production cost. Carbon nanotubes and graphene can be combined to provide an effective three-dimensional material with high conductivity and high surface area. We demonstrate the use of block copolymers to obtain patterned arrays of iron nanoparticles which give rise to ordered carbon nanotubes with good size distribution. A one-step chemical vapor deposition process for large-area fabrication of the graphene and carbon nanotube hybrid structure is described. Following chemical vapor deposition the hybrid material is demonstrated in a supercapacitor device. The fabricated supercapacitor exhibits high electrical conductivity, and has potential for extremely high energy storage capability.

scholarly journals NGC 3894: a young radio galaxy seen by Fermi-LAT

2020 ◽  
Vol 635 ◽  
pp. A185 ◽  
Author(s):  
G. Principe ◽  
G. Migliori ◽  
T. J. Johnson ◽  
F. D’Ammando ◽  
M. Giroletti ◽  
...  
Keyword(s):  
Radio Galaxy ◽  
Radio Galaxies ◽  
High Energy ◽  
Apparent Velocity ◽  
Large Area ◽  
Long Baseline ◽  
Full Period ◽  
Very Long Baseline Array ◽  
High Energy Emission ◽  
First Time

Context. According to radiative models, radio galaxies may produce γ-ray emission from the first stages of their evolution. However, very few such galaxies have been detected by the Fermi Large Area Telescope (LAT) so far. Aims. NGC 3894 is a nearby (z = 0.0108) object that belongs to the class of compact symmetric objects (CSOs, i.e., the most compact and youngest radio galaxies), which is associated with a γ-ray counterpart in the Fourth Fermi-LAT source catalog. Here we present a study of the source in the γ-ray and radio bands aimed at investigating its high-energy emission and assess its young nature. Methods. We analyzed 10.8 years of Fermi-LAT data between 100 MeV and 300 GeV and determined the spectral and variability characteristics of the source. Multi-epoch very long baseline array (VLBA) observations between 5 and 15 GHz over a period of 35years were used to study the radio morphology of NGC 3894 and its evolution. Results. NGC 3894 is detected in γ-rays with a significance >9σ over the full period, and no significant variability has been observed in the γ-ray flux on a yearly time-scale. The spectrum is modeled with a flat power law (Γ = 2.0 ± 0.1) and a flux on the order of 2.2 × 10−9 ph cm−2 s−1. For the first time, the VLBA data allow us to constrain with high precision the apparent velocity of the jet and counter-jet side to be βapp, NW = 0.132 ± 0.004 and βapp, SE = 0.065 ± 0.003, respectively. Conclusions. Fermi-LAT and VLBA results favor the youth scenario for the inner structure of this object, with an estimated dynamical age of 59 ± 5 years. The estimated range of viewing angle (10° < θ <  21°) does not exclude a possible jet-like origin of the γ-ray emission.

scholarly journals Detection of a flaring blazar coincident with an IceCube high-energy neutrino

2019 ◽  
Vol 207 ◽  
pp. 02001
Author(s):  
Anna Franckowiak
Keyword(s):  
Gamma Ray ◽  
Spectral Energy Distribution ◽  
Neutrino Flux ◽  
High Energy ◽  
Spectral Energy ◽  
Large Area ◽  
High Energy Neutrino ◽  
Energy Neutrino ◽  
Radio Wavelength ◽  
First Time

In September 22, 2017, IceCube released a public alert announcing the detection of a 290 TeV neutrino track event with an angular uncertainty of one square degree (90% containment). A multi-messenger follow-up campaign was initiated resulting in the detection of a GeV gamma-ray flare by the Fermi Large Area Telescope positionally consistent with the location of the known Bl Lac object, TXS 0506+056 , located only 0.1 degrees from the best-fit neutrino position. The probability of finding a GeV gamma-ray flare in coincidence with a high-energy neutrino event assuming a correlation of the neutrino flux with the gamma-ray energy flux in the energy band between 1 and 100 GeV was calculated to be 3σ (after trials correction). Following the detection of the flaring blazar the imaging air Cherenkov telescope MAGIC detected the source for the first time in the > 100 GeV gamma-ray band. The activity of the source was confirmed in X-ray, optical and radio wavelength. Several groups have developed lepto-hadronic models which succeed to explain the multi-messenger spectral energy distribution.

Synchronous chemical vapor deposition of large-area hybrid graphene–carbon nanotube architectures

2013 ◽  
Vol 28 (7) ◽  
pp. 958-968 ◽  
Author(s):  
Maziar Ghazinejad ◽  
Shirui Guo ◽  
Wei Wang ◽  
Mihrimah Ozkan ◽  
Cengiz S. Ozkan
Keyword(s):  
Chemical Vapor Deposition ◽  
Carbon Nanotube ◽  
Vapor Deposition ◽  
Chemical Vapor ◽  
Large Area ◽  
Image Position

Abstract

A large-area bent crystal shield for deflection of high-energy ions

2007 ◽  
Vol 91 (26) ◽  
pp. 261901 ◽  
Author(s):  
M. B. H. Breese
Keyword(s):  
High Energy ◽  
Large Area ◽  
Bent Crystal ◽  
High Energy Ions

Passivation of InGaAs/InP heterostructures

1999 ◽  
Vol 573 ◽  
Author(s):  
R. Driad ◽  
Z. H. Lu ◽  
W. R. McKinnon ◽  
S. Laframboise ◽  
S. P. McAlister ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Layer Structure ◽  
Chemical Vapor ◽  
High Energy ◽  
Current Gain ◽  
Ozone Treatment ◽  
High Energy Resolution ◽  
Large Area ◽  
Extrinsic Base ◽  
Uv Ozone

ABSTRACTIn this study we report different surface treatments and device designs that can be used to improve the performance of InGaAs/InP heterostructure devices. The surface properties of InGaAs (100) after sulfur or UV-ozone passivation were investigated by photoluminescence and high energy-resolution X-ray photoelectron spectroscopy. The base leakage current and the dc current gain of InGaAs/InP heterostructure bipolar transistors (HBTs) have been used to evaluate the efficiency of the passivation treatments. Although these treatments successfully passivated large area HBTs, the improved device characteristics degraded after a dielectric was deposited by plasma enhanced chemical vapor deposition (PECVD) or even just with time. Nevertheless, we found a combined surface treatment that is successful even under PECVD deposition – a UV-ozone treatment that produces a sacrificial oxide that is then removed by HF. This approach will be contrasted with a different method based on an optimized HBT layer structure with a thin InP emitter. In this case, the thin layer of depleted InP from the emitter left on the extrinsic base passivates the surface, and no treatment is required.

High-Efficiency, Thin-Film GaAs Solar Cells

1983 ◽  
Vol 105 (3) ◽  
pp. 237-242 ◽  
Author(s):  
S. Zwerdling ◽  
K. L. Wang ◽  
Y. C. M. Yeh
Keyword(s):  
Solar Cells ◽  
Conversion Efficiency ◽  
High Efficiency ◽  
Weight Ratio ◽  
Chemical Vapor ◽  
Oxide Semiconductor ◽  
Large Area ◽  
Coated Metal ◽  
Cvd Growth ◽  
First Time

The present research is directed toward demonstrating the feasibility of producing high-efficiency GaAs solar cells with high power-to-weight ratio by organo-metallic chemical vapor deposition (OM-CVD) growth of thin epi-layers on suitable substrates. Antireflection-coated, metal-oxide-semiconductor (AMOS), GaAs solar cells grown on bulk polycrystalline Ge substrates were initially studied, with the best efficiency achieved being about 9 percent AM1 (7 percent AM0). Subsequently, a new direct deposition method for fabricating ultra-thin top layer, epitaxial n+ /p shallow homojunction solar cells on (100) GaAs substrates (without anodic thinning) was developed by means of which large area (1 cm2) cells were produced with about 19 percent AM1 (15 percent AM0) conversion efficiency. An AM1 conversion efficiency of about 18 percent (14 percent AM0), or about 17 percent (13 percent AM0) with 5 percent grid coverage, was achieved for a single-crystal, GaAs, n+ /p cell grown by OM-CVD on a Ge wafer. These achievements led to the fabrication, for the first time, of thin GaAs epi-layers OM-CVD grown with good crystallographic quality, using a (100) Si-substrate on which a thin Ge epi-interlayer was first deposited by CVD from GeH4 and processed for improved surface morphology.

HIGH FREQUENCY GRAPHENE TRANSISTORS USING LARGE-AREA CVD GRAPHENE AND ADVANCED DIELECTRICS

2011 ◽  
Vol 20 (03) ◽  
pp. 669-677
Author(s):  
OSAMA M. NAYFEH ◽  
TONY IVANOV ◽  
JAMES WILSON ◽  
ROBERT PROIE ◽  
MADAN DUBEY
Keyword(s):  
High Frequency ◽  
Gate Dielectric ◽  
Chemical Vapor ◽  
Hole Mobility ◽  
Monolayer Graphene ◽  
Large Area ◽  
Cvd Graphene ◽  
Ambipolar Behavior ◽  
Chemical Vapor Deposited ◽  
First Time

Graphene transistors using large area chemical-vapor-deposited (CVD) monolayer graphene and advanced dielectric stacks are constructed and examined. Top-gated devices with a SiO 2/ Al 2 O 3 gate-dielectric have a Dirac Point (DP) located at less than 5 V and asymmetric electron/hole mobility. In contrast, devices based on an advanced AlN interfacial layer have a DP located near 0V and a near symmetric carrier mobility- characteristics that could be more suitable for applications that require ambipolar behavior and low-power operation. For the first time, a measured RF cut-off frequency range of 1GHz is measured for top-gated transistors using CVD graphene. The results are of importance for the realization of graphene based, wafer-scale, high frequency electronics.

Preparation and Characterisation of an Aligned Carbon Nanotube Array on the Ni-Deposited Silicon Surface

2010 ◽  
Vol 152-153 ◽  
pp. 722-725
Author(s):  
Gang Li ◽  
Wen Ming Cheng
Keyword(s):  
Carbon Nanotube ◽  
Chemical Vapor ◽  
Ni Catalyst ◽  
Silicon Substrates ◽  
Large Area ◽  
Sem Images ◽  
Experimental Conditions ◽  
Average Growth ◽  
Catalyst Film ◽  
Vapor Deposition Technique

An aligned carbon nanotube（CNT）array has been prepared on large area Ni-deposited silicon substrates via the pyrolysis of C2H2 using thermal chemical vapor deposition technique at 900°C. Ni nanoparticles were formed when Ni catalyst film was etched and conglomerated by NH3 pretreatment. Under the experimental conditions used, scanning electron microscope (SEM) images showed the CNTs films with 3090 nm in diameter and 17 m in length grown perpendicular to the surface of the substrates at an average growth rate of 102 m/h. Energy dispersive X-ray (EDX) spectrum is carried out to identify the composition of the CNTs and EDX analysis demonstrated that the CNTs are formed as tip growth.

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