Accumulation and Recovery of Irradiation Effects in Silicon Carbide

1998 ◽  
Vol 540 ◽  
Author(s):  
W.J. Weber ◽  
W. Jiang ◽  
S. Thevuthasan ◽  
D.E. Mecready
Keyword(s):  
Activation Energy ◽  
Damage Accumulation ◽  
Room Temperature ◽  
Rutherford Backscattering Spectrometry ◽  
Complete Recovery ◽  
Structural Disorder ◽  
Dose Dependence ◽  
Thermal Recovery ◽  
Recovery Processes ◽  
Wide Range

AbstractSingle crystals of 6H-SiC have been irradiated with a variety of ions over a wide range of fluences and temperatures. The temperature and dose dependence of damage accumulation has been investigated using in-situ Rutherford Backscattering Spectrometry in channeling geometry. At low temperatures, the accumulation of structural disorder exhibits a sigmoidal dependence on dose. At room temperature and higher, simultaneous recovery processes during irradiation significantly reduce the damage accumulation rates by up to a factor of five. Isochronal and isothermal annealing studies have been used to study the damage recovery behavior. For low defect concentrations introduced by 550 keV Si+ irradiation at 160 K, complete recovery is observed at 300 K. However, defects introduced by He+ irradiation on the Si sublattice are more difficult to anneal at room temperature, which suggests trapping of the implanted helium may inhibit defect recombination. Below room temperature, the thermal recovery of defects on the Si sublattice has an activation energy on the order of 0.3 ± 0.1 eV. Defect recovery above 570 K has an activation energy on the order of 1.5 ± 0.3 eV.

Damage Accumulation and Thermal Recovery in SrTiO3 Implanted with Au2+ Ions

1998 ◽  
Vol 540 ◽  
Author(s):  
S. Thevuthasan ◽  
W. Jiang ◽  
W.J. Weber ◽  
D.E. McCready
Keyword(s):  
Single Crystal ◽  
Damage Accumulation ◽  
Rutherford Backscattering Spectrometry ◽  
Recovery Process ◽  
Thermal Recovery ◽  
Broad Temperature Range ◽  
Maximum Temperature ◽  
Recovery Processes ◽  
Annealing Experiments

AbstractDamage accumulation and recovery process have been investigated in single crystal SrTiO3 irradiated with 1.0 MeV Au2+ using in-situ Rutherford Backscattering Spectrometry (RBS) in Channeling geometry. Samples were irradiated at a temperature of 200 K with ion fluences ranging from 5.0×1013 2.5×1014Au2+/cm2 (0.22 – 1.10 dpa at damage peak). Subsequent isochronal annealing experiments were performed to study damage recovery processes up to a maximum temperature of 870 K. At an ion fluence between 2.0–2.5×1014Au2+/cm2 (0.88 – 1.10 dpa), the implanted region, which is just below the surface, becomes amorphous. The recovery processes occur over a broad temperature range, and the damage created by low ion fluences, 5.0×1013 − 1.0×1014 Au2+/cm2, is almost completely recovered after annealing at 870 K.

scholarly journals OPTICAL DOPING OF NITRIDES BY ION IMPLANTATION

2001 ◽  
Vol 15 (28n29) ◽  
pp. 1281-1287 ◽  
Author(s):  
E. ALVES ◽  
K. LORENZ ◽  
R. VIANDEN ◽  
C. BOEMARE ◽  
M. J. SOARES ◽  
...  
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Room Temperature ◽  
Lattice Site ◽  
Rutherford Backscattering Spectrometry ◽  
Complete Recovery ◽  
Nitrogen Atmosphere ◽  
Site Location ◽  
Damage Behavior ◽  
Recombination Processes

A series of rare earth elements (RE) were implanted in GaN epilayers to study the lattice site location and optical activity. Rutherford backscattering spectrometry in the channeling mode (RBS/C) was used to follow the damage behavior in the Ga sublattice and the site location of the RE. For all the implanted elements (Ce, Pr, Dy, Er, and Lu) the results indicate the complete substitutionality on Ga sites after rapid thermal annealing at 1000°C for 2 min. The only exception occurs for Eu, which occupies a Ga displaced site. Annealing at 1200°C in nitrogen atmosphere at a pressure of 1GPa is necessary to achieve the complete recovery of the damage in the samples. After annealing the recombination processes of the implanted samples were studied by above and below band gap excitation. For Er implanted samples besides the 1.54 μm emission green and red emissions are also observed. Red emissions from 5 D 0 → 7 F 2 and 3 P 0 → 3 F 2 transitions were found in Eu and Pr implanted samples even at room temperature.

Electron Paramagnetic Resonance in Cu2O Compared with Other Semiconducting Properties

1971 ◽  
Vol 49 (10) ◽  
pp. 1275-1283 ◽  
Author(s):  
J. C. W. Taylor ◽  
F. L. Weichman ◽  
R. E. D. McClung
Keyword(s):  
Activation Energy ◽  
Electron Paramagnetic Resonance ◽  
Single Crystals ◽  
Room Temperature ◽  
Starting Material ◽  
Paramagnetic Resonance ◽  
Semiconducting Properties ◽  
Wide Range ◽  
Temperature Activation ◽  
Electron Paramagnetic

Electron paramagnetic resonance spectra have been observed in single crystals of Cu2O at 4.2 °K. Six samples cut from the same starting material were individually heated under a wide range of vacuum conditions and comparison was made between the observed e.p.r. spectrum and the luminescence, activation energy, and photoconductivity in the same sample. No direct relationships between e.p.r. spectra and the luminescence and photoconductivity were found although a good correlation between the complexity of the e.p.r. spectra and the room temperature activation energy was observed.

scholarly journals Combined experimental-theoretical study of electron mobility-limiting mechanisms in SrSnO3

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Tristan K. Truttmann ◽  
Jin-Jian Zhou ◽  
I-Te Lu ◽  
Anil Kumar Rajapitamahuni ◽  
Fengdeng Liu ◽  
...  
Keyword(s):  
Carrier Concentration ◽  
Room Temperature ◽  
Structural Disorder ◽  
Perovskite Oxide ◽  
Epitaxial Thin Films ◽  
Power Sources ◽  
Limited Mobility ◽  
Renewable Power ◽  
Wide Range ◽  
High Carrier Mobility

AbstractThe discovery and development of ultra-wide bandgap (UWBG) semiconductors is crucial to accelerate the adoption of renewable power sources. This necessitates an UWBG semiconductor that exhibits robust doping with high carrier mobility over a wide range of carrier concentrations. Here we demonstrate that epitaxial thin films of the perovskite oxide NdxSr1−xSnO3 (SSO) do exactly this. Nd is used as a donor to successfully modulate the carrier concentration over nearly two orders of magnitude, from 3.7 × 1018 cm−3 to 2.0 × 1020 cm−3. Despite being grown on lattice-mismatched substrates and thus having relatively high structural disorder, SSO films exhibited the highest room-temperature mobility, ~70 cm2 V−1 s−1, among all known UWBG semiconductors in the range of carrier concentrations studied. The phonon-limited mobility is calculated from first principles and supplemented with a model to treat ionized impurity and Kondo scattering. This produces excellent agreement with experiment over a wide range of temperatures and carrier concentrations, and predicts the room-temperature phonon-limited mobility to be 76–99 cm2 V−1 s−1 depending on carrier concentration. This work establishes a perovskite oxide as an emerging UWBG semiconductor candidate with potential for applications in power electronics.

Mechanical Properties and Dislocation Structure of Single Crystal Cdte Deformed in Compression at 300°C

1976 ◽  
Vol 34 ◽  
pp. 592-593
Author(s):  
Ernest L. Hall ◽  
J. B. Vander Sande
Keyword(s):  
Mechanical Properties ◽  
Single Crystal ◽  
Dislocation Structure ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Strain Curve ◽  
Optical Devices ◽  
Semiconductor Compound ◽  
Wide Range ◽  
Sample Orientation

The present paper describes research on the mechanical properties and related dislocation structure of CdTe, a II-VI semiconductor compound with a wide range of uses in electrical and optical devices. At room temperature CdTe exhibits little plasticity and at the same time relatively low strength and hardness. The mechanical behavior of CdTe was examined at elevated temperatures with the goal of understanding plastic flow in this material and eventually improving the room temperature properties. Several samples of single crystal CdTe of identical size and crystallographic orientation were deformed in compression at 300°C to various levels of total strain. A resolved shear stress vs. compressive glide strain curve (Figure la) was derived from the results of the tests and the knowledge of the sample orientation.

Evaluation of 99mTc-Label led Vitamin K4 as an Agent for Testicular Imaging

1991 ◽  
Vol 30 (01) ◽  
pp. 35-39 ◽  
Author(s):  
H. S. Durak ◽  
M. Kitapgi ◽  
B. E. Caner ◽  
R. Senekowitsch ◽  
M. T. Ercan
Keyword(s):  
Soft Tissue ◽  
Room Temperature ◽  
Normal Subjects ◽  
Left Testis ◽  
Wide Range ◽  
Activity Ratios ◽  
The Right ◽  
Radioactivity Levels

Vitamin K4 was labelled with 99mTc with an efficiency higher than 97%. The compound was stable up to 24 h at room temperature, and its biodistribution in NMRI mice indicated its in vivo stability. Blood radioactivity levels were high over a wide range. 10% of the injected activity remained in blood after 24 h. Excretion was mostly via kidneys. Only the liver and kidneys concentrated appreciable amounts of radioactivity. Testis/soft tissue ratios were 1.4 and 1.57 at 6 and 24 h, respectively. Testis/blood ratios were lower than 1. In vitro studies with mouse blood indicated that 33.9 ±9.6% of the radioactivity was associated with RBCs; it was washed out almost completely with saline. Protein binding was 28.7 ±6.3% as determined by TCA precipitation. Blood clearance of 99mTc-l<4 in normal subjects showed a slow decrease of radioactivity, reaching a plateau after 16 h at 20% of the injected activity. In scintigraphic images in men the testes could be well visualized. The right/left testis ratio was 1.08 ±0.13. Testis/soft tissue and testis/blood activity ratios were highest at 3 h. These ratios were higher than those obtained with pertechnetate at 20 min post injection.99mTc-l<4 appears to be a promising radiopharmaceutical for the scintigraphic visualization of testes.

The Influence of Ultra-Low Concentrations of Potassium Anphen on the Bioenergetic Characteristics of Mitochondria

2020 ◽  
Vol 16 (4) ◽  
pp. 537-542
Author(s):  
Zhigacheva Irina ◽  
Volodkin Aleksandr ◽  
Rasulov Maksud
Keyword(s):  
Functional State ◽  
Membrane Lipids ◽  
Biological Effects ◽  
Dose Dependence ◽  
Stress Factors ◽  
Mitochondrial Membranes ◽  
Oxidation Rates ◽  
Pea Seedlings ◽  
Low Concentrations ◽  
Wide Range

Background: One of the main sources of ROS in stress conditions is the mitochondria. Excessive generation of ROS leads to oxidation of thiol groups of proteins, peroxidation of membrane lipids and swelling of the mitochondria. In this regard, there is a need to search for preparationsadaptogens that increase the body's resistance to stress factors. Perhaps, antioxidants can serve as such adaptogens. This work aims at studying the effect of antioxidant; the potassium anphen in a wide range of concentrations on the functional state of 6 day etiolated pea seedlings mitochondria (Pisum sativum L). Methods: The functional state of mitochondria was studied per rates of mitochondria respiration, by the level of lipid peroxidation and study of fatty acid composition of mitochondrial membranes by chromatography technique. Results: Potassium anphen in concentrations of 10-5 - 10-8 M and 10-13-10-16 prevented the activation of LPO in the mitochondrial membranes of pea seedlings, increased the oxidation rates of NAD-dependent substrates and succinate in the respiratory chain of mitochondria that probably pointed to the anti-stress properties of the drug. Indeed, the treatment of pea seeds with the preparation in concentrations of 10-13 M prevented the inhibition of growth of seedlings in conditions of water deficiency. Conclusion: It is assumed that the dose dependence of the biological effects of potassium anphen and the manifestation of these effects in ultra-low concentrations are due to its ability in water solutions to form a hydrate containing molecular ensembles (structures).

On the use of Ozawa/Flynn/Wall method to determine aging activation energy for elastomers

2021 ◽  
pp. 009524432110203
Author(s):  
Sudhir Bafna
Keyword(s):  
Mechanical Properties ◽  
Activation Energy ◽  
Weight Loss ◽  
Oxygen Consumption ◽  
Dwell Time ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Degradation Mechanism ◽  
Kinetics Of ◽  
Wall Method

It is often necessary to assess the effect of aging at room temperature over years/decades for hardware containing elastomeric components such as oring seals or shock isolators. In order to determine this effect, accelerated oven aging at elevated temperatures is pursued. When doing so, it is vital that the degradation mechanism still be representative of that prevalent at room temperature. This places an upper limit on the elevated oven temperature, which in turn, increases the dwell time in the oven. As a result, the oven dwell time can run into months, if not years, something that is not realistically feasible due to resource/schedule constraints in industry. Measuring activation energy (Ea) of elastomer aging by test methods such as tensile strength or elongation, compression set, modulus, oxygen consumption, etc. is expensive and time consuming. Use of kinetics of weight loss by ThermoGravimetric Analysis (TGA) using the Ozawa/Flynn/Wall method per ASTM E1641 is an attractive option (especially due to the availability of commercial instrumentation with software to make the required measurements and calculations) and is widely used. There is no fundamental scientific reason why the kinetics of weight loss at elevated temperatures should correlate to the kinetics of loss of mechanical properties over years/decades at room temperature. Ea obtained by high temperature weight loss is almost always significantly higher than that obtained by measurements of mechanical properties or oxygen consumption over extended periods at much lower temperatures. In this paper, data on five different elastomer types (butyl, nitrile, EPDM, polychloroprene and fluorocarbon) are presented to prove that point. Thus, use of Ea determined by weight loss by TGA tends to give unrealistically high values, which in turn, will lead to incorrectly high predictions of storage life at room temperature.

Porphyrin-Catalyzed Oxidation of N-Substituted Tetrahydroisoquinolines to Dihydroisoquinolones

Synlett ◽  
2021 ◽  
Author(s):  
Ao Li ◽  
Bin Pan ◽  
Mu Chao ◽  
Na Wang ◽  
Yu-Long Li ◽  
...  
Keyword(s):  
Visible Light ◽  
Room Temperature ◽  
Air Atmosphere ◽  
Wide Range ◽  
Convenient Route ◽  
Catalyzed Oxidation

A visible-light-induced direct α-oxygenation of N-substituted tetrahydroisoquinoline derivatives has been successfully developed. Metalloporphyrin (ZnTPP) has been identified as an effective and inexpensive photocatalyst for this transformation with a wide range of substrates. This protocol provides a convenient route to afford the desired products in moderate to good yields at room temperature under air atmosphere.

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