| 1. |
- Ruilope, LM, et al.
(författare)
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Design and Baseline Characteristics of the Finerenone in Reducing Cardiovascular Mortality and Morbidity in Diabetic Kidney Disease Trial
- 2019
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Ingår i: American journal of nephrology. - : S. Karger AG. - 1421-9670 .- 0250-8095. ; 50:5, s. 345-356
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Tidskriftsartikel (refereegranskat)abstract
- <b><i>Background:</i></b> Among people with diabetes, those with kidney disease have exceptionally high rates of cardiovascular (CV) morbidity and mortality and progression of their underlying kidney disease. Finerenone is a novel, nonsteroidal, selective mineralocorticoid receptor antagonist that has shown to reduce albuminuria in type 2 diabetes (T2D) patients with chronic kidney disease (CKD) while revealing only a low risk of hyperkalemia. However, the effect of finerenone on CV and renal outcomes has not yet been investigated in long-term trials. <b><i>Patients and</i></b> <b><i>Methods:</i></b> The Finerenone in Reducing CV Mortality and Morbidity in Diabetic Kidney Disease (FIGARO-DKD) trial aims to assess the efficacy and safety of finerenone compared to placebo at reducing clinically important CV and renal outcomes in T2D patients with CKD. FIGARO-DKD is a randomized, double-blind, placebo-controlled, parallel-group, event-driven trial running in 47 countries with an expected duration of approximately 6 years. FIGARO-DKD randomized 7,437 patients with an estimated glomerular filtration rate ≥25 mL/min/1.73 m<sup>2</sup> and albuminuria (urinary albumin-to-creatinine ratio ≥30 to ≤5,000 mg/g). The study has at least 90% power to detect a 20% reduction in the risk of the primary outcome (overall two-sided significance level α = 0.05), the composite of time to first occurrence of CV death, nonfatal myocardial infarction, nonfatal stroke, or hospitalization for heart failure. <b><i>Conclusions:</i></b> FIGARO-DKD will determine whether an optimally treated cohort of T2D patients with CKD at high risk of CV and renal events will experience cardiorenal benefits with the addition of finerenone to their treatment regimen. Trial Registration: EudraCT number: 2015-000950-39; ClinicalTrials.gov identifier: NCT02545049.
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| 2. |
- Leleu, A., et al.
(författare)
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Six transiting planets and a chain of Laplace resonances in TOI-178
- 2021
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 649
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Tidskriftsartikel (refereegranskat)abstract
- Determining the architecture of multi-planetary systems is one of the cornerstones of understanding planet formation and evolution. Resonant systems are especially important as the fragility of their orbital configuration ensures that no significant scattering or collisional event has taken place since the earliest formation phase when the parent protoplanetary disc was still present. In this context, TOI-178 has been the subject of particular attention since the first TESS observations hinted at the possible presence of a near 2:3:3 resonant chain. Here we report the results of observations from CHEOPS, ESPRESSO, NGTS, and SPECULOOS with the aim of deciphering the peculiar orbital architecture of the system. We show that TOI-178 harbours at least six planets in the super-Earth to mini-Neptune regimes, with radii ranging from 1.152 to 2.87 Earth radii and periods of 1.91, 3.24, 6.56, 9.96, 15.23, and 20.71 days. All planets but the innermost one form a 2:4:6:9:12 chain of Laplace resonances, and the planetary densities show important variations from planet to planet, jumping from 1.02 to 0.177 times the Earth's density between planets c and d. Using Bayesian interior structure retrieval models, we show that the amount of gas in the planets does not vary in a monotonous way, contrary to what one would expect from simple formation and evolution models and unlike other known systems in a chain of Laplace resonances. The brightness of TOI-178 (H = 8.76 mag, J = 9.37 mag, V = 11.95 mag) allows for a precise characterisation of its orbital architecture as well as of the physical nature of the six presently known transiting planets it harbours. The peculiar orbital configuration and the diversity in average density among the planets in the system will enable the study of interior planetary structures and atmospheric evolution, providing important clues on the formation of super-Earths and mini-Neptunes. -0.070 -0.13 -0.23 -0.061 +0.073 +0.14 +0.28 +0.055
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| 3. |
- Fuselier, S. A., et al.
(författare)
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Large-scale characteristics of reconnection diffusion regions and associated magnetopause crossings observed by MMS
- 2017
-
Ingår i: Journal of Geophysical Research - Space Physics. - 2169-9380 .- 2169-9402. ; 122:5, s. 5466-5486
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Tidskriftsartikel (refereegranskat)abstract
- The Magnetospheric Multiscale (MMS) mission was designed to make observations in the very small electron diffusion region (EDR), where magnetic reconnection takes place. From a data set of over 4500 magnetopause crossings obtained in the first phase of the mission, MMS had encounters near or within 12 EDRs. These 12 events and associated magnetopause crossings are considered as a group to determine if they span the widest possible range of external and internal conditions (i.e., in the solar wind and magnetosphere). In addition, observations from MMS are used to determine if there are multiple X-lines present and also to provide information on X-line location relative to the spacecraft. These 12 events represent nearly the widest possible range of conditions at the dayside magnetopause. They occur over a wide range of local times and magnetic shear angles between the magnetosheath and magnetospheric magnetic fields. Most show evidence for multiple reconnection sites.
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| 4. |
- Lee, Justin H., et al.
(författare)
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MMS Measurements and Modeling of Peculiar Electromagnetic Ion Cyclotron Waves
- 2019
-
Ingår i: Geophysical Research Letters. - : AMER GEOPHYSICAL UNION. - 0094-8276 .- 1944-8007.
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Tidskriftsartikel (refereegranskat)abstract
- Orbiting Earth's dayside outer magnetosphere on 29 September 2015, the Magnetospheric Multiscale (MMS) satellites measured plasma composition, simultaneous electromagnetic ion cyclotron waves, and intermittent fast plasma flows consistent with ultralow frequency waves or convection. Such flows can accelerate typically unobservable low-energy plasma into a measurable energy range of spacecraft plasma instrumentation. We exploit the flow occurrence to ensure measurement of cold ion species alongside the hot particles-consisting of ionospheric heavy ions and solar wind He++-during a subinterval of wave emissions with spectral properties previously described as peculiar. Through application of the composition and multisatellite wave vector data to linear theory, we demonstrate the emissions are in fact consistent with theory, growing naturally in the He++ band with sufficient free energy.
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| 5. |
- Nielsen, L. D., et al.
(författare)
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Mass determinations of the three mini-Neptunes transiting TOI-125
- 2020
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 492:4, s. 5399-5412
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Tidskriftsartikel (refereegranskat)abstract
- The Transiting Exoplanet Survey Satellite, TESS, is currently carrying out an all-sky search for small planets transiting bright stars. In the first year of the TESS survey, a steady progress was made in achieving the mission's primary science goal of establishing bulk densities for 50 planets smaller than Neptune. During that year, the TESS's observations were focused on the southern ecliptic hemisphere, resulting in the discovery of three mini-Neptunes orbiting the star T01-125, a V = 11,0 KO dwarf. We present intensive HARPS radial velocity observations, yielding precise mass measurements for TO1-125b, TOI-125c, and TOI-125d. TOI-125b has an orbital period of 4,65 d, a radius of 2,726 + 0,075 RE, a mass of 9,50 0,88 ME, and is near the 2:1 mean motion resonance with TOI-125c at 9.15 d. TOI-125c has a similar radius of 2,759 0.10 RE and a mass of 6,63 + 0,99 ME, being the puffiest of the three planets. T01-125d has an orbital period of 19,98 d and a radius of 2.93 + 0,17 RE and mass 13,6 1,2 ME, For T01-125b and d, we find unusual high eccentricities of 0.19 0.04 and 0.17+(c):(!,(, respectively. Our analysis also provides upper mass limits for the two low-SNR planet candidates in the system; for T01-125.04 (Rp = 1.36 RE, P = 0.53 d), we find a 2a upper mass limit of 1.6 ME, whereas T01-125.05 (RP = 4.2-'2E44 RE, P = 13.28 d) is unlikely a viable planet candidate with an upper mass limit of 2.7 ME. We discuss the internal structure of the three confirmed planets, as well as dynamical stability and system architecture for this intriguing exoplanet system.
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| 6. |
- Denton, R. E., et al.
(författare)
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Determining L-M-N Current Sheet Coordinates at the Magnetopause From Magnetospheric Multiscale Data
- 2018
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Ingår i: Journal of Geophysical Research - Space Physics. - : AMER GEOPHYSICAL UNION. - 2169-9380 .- 2169-9402. ; 123:3, s. 2274-2295
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Tidskriftsartikel (refereegranskat)abstract
- We discuss methods to determine L-M-N coordinate systems for current sheet crossings observed by the Magnetospheric Multiscale (MMS) spacecraft mission during ongoing reconnection, where e(L) is the direction of the reconnecting component of the magnetic field, B, and e(N) is normal to the magnetopause. We present and test a new hybrid method, with e(L) estimated as the maximum variance direction of B (MVAB) and e(N) as the direction of maximum directional derivative of B, and then adjust these directions to be perpendicular. In the best case, only small adjustment is needed. Results from this method, applied to an MMS crossing of the dayside magnetopause at 1305:45UT on 16 October 2015, are discussed and compared with those from other methods for which e(N) is obtained by other means. Each of the other evaluations can be combined with e(L) from MVAB in a generalized hybrid approach to provide an L-M-N system. The quality of the results is judged by eigenvalue ratios, constancy of directions using different data segments and methods, and expected sign and magnitude of the normal component of B. For this event, the hybrid method appears to produce e(N) accurate to within less than 10 degrees. We discuss variance analysis using the electric current density, J, or the J x B force, which yield promising results, and minimum Faraday residue analysis and MVAB alone, which can be useful for other events. We also briefly discuss results from our hybrid method and MVAB alone for a few other MMS reconnection events. Plain Language Summary We discuss methods for determining coordinate systems in order to study magnetic reconnection events at the magnetopause, the boundary between the ionized gas in the region of space dominated by the Earth's magnetic field and the ionized gas coming from the solar wind. We introduce a new method that combines results from multiple methods in order to determine the three coordinate directions in space. We demonstrate this method by applying it to an event observed by the Magnetospheric Multiscale spacecraft on 16 October 2015 and at other times.
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| 7. |
- Fuselier, S. A., et al.
(författare)
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High-density O+ in Earth's outer magnetosphere and its effect on dayside magnetopause magnetic reconnection
- 2019
-
Ingår i: Journal of Geophysical Research - Space Physics. - : AMER GEOPHYSICAL UNION. - 2169-9380 .- 2169-9402. ; 124:12, s. 10257-10269
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Tidskriftsartikel (refereegranskat)abstract
- The warm plasma cloak is a source of magnetospheric plasma that contain significant O+. When the O+ density in the magnetosphere near the magnetopause is >0.2 cm(-3) and the H+ density is <1.5 cm(-3), then O+ dominates the magnetospheric ion mass density by more than a factor of 2. A survey is conducted of such O+-rich warm plasma cloak intervals and their effect on reconnection at the Earth's magnetopause. The survey uses data from the Magnetospheric Multiscale mission (MMS) and the results are compared and combined with a previous survey of the warm plasma cloak. Overall, the warm plasma cloak and the O+-rich warm plasma cloak reduce the magnetopause reconnection rate by >20% due to mass-loading only about 2% to 4% of the time. However, during geomagnetic storms, O+ dominates the mass density of the warm plasma cloak and these mass densities are very high. Therefore, a separate study is conducted to determine the effect of the warm plasma cloak on magnetopause reconnection during geomagnetically disturbed times. This study shows that the warm plasma cloak reduces the reconnection rate significantly about 25% of the time during disturbed conditions.
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| 8. |
- Fuselier, S. A., et al.
(författare)
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Mass Loading the Earth's Dayside Magnetopause Boundary Layer and Its Effect on Magnetic Reconnection
- 2019
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Ingår i: Geophysical Research Letters. - : AMER GEOPHYSICAL UNION. - 0094-8276 .- 1944-8007. ; 46:12, s. 6204-6213
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Tidskriftsartikel (refereegranskat)abstract
- When the interplanetary magnetic field is northward for a period of time, O+ from the high-latitude ionosphere escapes along reconnected magnetic field lines into the dayside magnetopause boundary layer. Dual-lobe reconnection closes these field lines, which traps O+ and mass loads the boundary layer. This O+ is an additional source of magnetospheric plasma that interacts with magnetosheath plasma through magnetic reconnection. This mass loading and interaction is illustrated through analysis of a magnetopause crossing by the Magnetospheric Multiscale spacecraft. While in the O+-rich boundary layer, the interplanetary magnetic field turns southward. As the Magnetospheric Multiscale spacecraft cross the high-shear magnetopause, reconnection signatures are observed. While the reconnection rate is likely reduced by the mass loading, reconnection is not suppressed at the magnetopause. The high-latitude dayside ionosphere is therefore a source of magnetospheric ions that contributes often to transient reduction in the reconnection rate at the dayside magnetopause.
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| 9. |
- Lee, Justin H., et al.
(författare)
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Application of Cold and Hot Plasma Composition Measurements to Investigate Impacts on Dusk-Side Electromagnetic Ion Cyclotron Waves
- 2021
-
Ingår i: Journal of Geophysical Research - Space Physics. - : American Geophysical Union (AGU). - 2169-9380 .- 2169-9402. ; 126:1
-
Tidskriftsartikel (refereegranskat)abstract
- An extended interval of perturbed magnetospheric conditions in November 2016 supported increased convection and sunward transport of plasmaspheric material. During this period of time the Magnetospheric Multiscale satellites, with their apogees along Earth's dusk-side outer magnetosphere, encountered several cold plasma density structures at the same time as plasma bulk flows capable of accelerating hidden cold plasma occurred. Investigating the charged particle and fields data during two subintervals showed that the satellites made direct measurements of cold plasmaspheric ions embedded within multicomponent hot plasmas as well as electromagnetic emissions consistent with electromagnetic ion cyclotron (EMIC) waves. The complex in situ ion composition measurements were applied to linear wave modeling to interpret the impacts of cold and hot ion species on wave growth and band structure. Although the waves for both intervals were predicted to have peak growth rate below omega(He+), substantial differences were observed among all other dispersive properties. The modeling also showed EMIC waves generated in the presence of heavy ions had growth rates and unstable wave numbers always smaller than predicted for a pure proton-electron plasma. The results provide implications for future investigation of EMIC wave generation with and without direct measurements of the cold and hot plasma composition as well as of subsequent wave-particle interactions.
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| 10. |
- Persson, Carina, 1964, et al.
(författare)
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TOI-2196 b: Rare planet in the hot Neptune desert transiting a G-type star
- 2022
-
Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 666
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Tidskriftsartikel (refereegranskat)abstract
- The hot Neptune desert is a region hosting a small number of short-period Neptunes in the radius-instellation diagram. Highly irradiated planets are usually either small (R less than or similar to 2 R-circle plus) and rocky or they are gas giants with radii of greater than or similar to 1 R-J. Here, we report on the intermediate-sized planet TOI-2196 b (TIC 372172128.01) on a 1.2 day orbit around a G-type star (V = 12.0, [Fe/H] = 0.14 dex) discovered by the Transiting Exoplanet Survey Satellite in sector 27. We collected 41 radial velocity measurements with the HARPS spectrograph to confirm the planetary nature of the transit signal and to determine the mass. The radius of TOI-2196 b is 3.51 +/- 0.15 R-circle plus, which, combined with the mass of 26.0 +/- 1.3 M-circle plus, results in a bulk density of 3.31(-0.43)(+0.51) g cm(-3). Hence, the radius implies that this planet is a sub-Neptune, although the density is twice than that of Neptune. A significant trend in the HARPS radial velocity measurements points to the presence of a distant companion with a lower limit on the period and mass of 220 days and 0.65 M-J, respectively, assuming zero eccentricity. The short period of planet b implies a high equilibrium temperature of 1860 +/- 20 K, for zero albedo and isotropic emission. This places the planet in the hot Neptune desert, joining a group of very few planets in this parameter space discovered in recent years. These planets suggest that the hot Neptune desert may be divided in two parts for planets with equilibrium temperatures of greater than or similar to 1800 K: a hot sub-Neptune desert devoid of planets with radii of approximate to 1.8-3 R-circle plus and a sub-Jovian desert for radii of approximate to 5-12 R-circle plus. More planets in this parameter space are needed to further investigate this finding. Planetary interior structure models of TOI-2196 b are consistent with a H/He atmosphere mass fraction between 0.4% and 3%, with a mean value of 0.7% on top of a rocky interior. We estimated the amount of mass this planet might have lost at a young age and we find that while the mass loss could have been significant, the planet had not changed in terms of character: it was born as a small volatile-rich planet and it remains one at present.
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| 11. |
- Toledo-Redondo, S., et al.
(författare)
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Kinetic Interaction of Cold and Hot Protons With an Oblique EMIC Wave Near the Dayside Reconnecting Magnetopause
- 2021
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Ingår i: Geophysical Research Letters. - : American Geophysical Union (AGU). - 0094-8276 .- 1944-8007. ; 48:8
-
Tidskriftsartikel (refereegranskat)abstract
- We report observations of the ion dynamics inside an Alfven branch wave that propagates near the reconnecting dayside magnetopause. The measured frequency, wave normal angle and polarization are consistent with the predictions of a dispersion solver. The magnetospheric plasma contains hot protons (keV), cold protons (eV), plus some heavy ions. While the cold protons follow the magnetic field fluctuations and remain frozen-in, the hot protons are at the limit of magnetization. The cold protons exchange energy back and forth, adiabatically, with the wave fields. The cold proton velocity fluctuations contribute to balance the Hall term fluctuations in Ohm's law, and the wave E field has small ellipticity and right-handed polarization. The dispersion solver indicates that increasing the cold proton density facilitates propagation and amplification of these waves at oblique angles, as for the observed wave. Plain Language Summary The Earth's magnetosphere is a very dilute cloud of charged particles that are trapped in the Earth's magnetic field. This cloud is surrounded by the solar wind, another very dilute gas that flows supersonically throughout the solar system. These two plasmas can couple to each other via magnetic reconnection, a fundamental plasma process that occurs at the dayside region of the interface between the two plasmas. When reconnection occurs, large amounts of energy and particles enter the magnetosphere, driving the near Earth space dynamics and generating, for instance, aurorae. The magnetospheric plasma sources are the solar wind and the Earth's ionosphere. Multiple plasma populations can be found inside the Earth's magnetosphere, depending on the plasma origin and its time history, as well as the magnetospheric forcing of the solar wind. In this study, we show how the presence of multiple particle populations at the interface between the solar wind and the magnetosphere modifies the properties of the waves that propagate there. Waves are known to play a fundamental role in converting energy and heating these very dilute charged gas clouds.
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| 12. |
- Vines, S. K., et al.
(författare)
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Magnetospheric Ion Evolution Across the Low-Latitude Boundary Layer Separatrix
- 2017
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Ingår i: Journal of Geophysical Research - Space Physics. - : Blackwell Publishing. - 2169-9380 .- 2169-9402. ; 122:10, s. 10247-10262
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Tidskriftsartikel (refereegranskat)abstract
- On 20 September 2015, the Magnetospheric Multiscale (MMS) spacecraft crossed the dusk magnetopause after a compression of the magnetosphere. Enhanced densities and fluxes of both colder (≤10 eV) and hotter (>1 keV) magnetospheric and magnetosheath heavy ion species were observed reaching the magnetopause. The evolution of the velocity distributions for H+, He+, and O+ measured by the Hot Plasma Composition Analyzer on MMS during this magnetopause crossing is presented. In particular, this study focuses on the changes in the species' distribution functions as MMS passes from the magnetosphere through the electron edge of the low-latitude boundary layer (LLBL) separatrix and then into the LLBL. Two types of processes are suggested to play a role in the heating of colder magnetospheric ions across the LLBL separatrix in the region between the separatrix and the electron and ion edges of the LLBL. One mechanism leads to the formation and enhancement of ring distributions in this layer of the LLBL as the magnetospheric ions propagate across the separatrix. A second mechanism leading first to perpendicular heating and then to parallel heating of colder protons may arise from a possible two-stream instability as the magnetospheric ions first encounter the warmer magnetosheath electrons in the electron layer and then the warmer magnetosheath ions between the electron and ion edges of the LLBL separatrix. Perpendicular heating of He+ and O+ is seen more so in the main reconnection exhaust, due to nonadiabatic behavior of these ions as they are accelerated up to the bulk flow speed.
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| 13. |
- Azarov, Alexander, et al.
(författare)
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Defect annealing kinetics in ZnO implanted with Zn substituting elements : Zn interstitials and Li redistribution
- 2019
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Ingår i: Journal of Applied Physics. - : AMER INST PHYSICS. - 0021-8979 .- 1089-7550. ; 125:7
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Tidskriftsartikel (refereegranskat)abstract
- It is known that the behavior of residual Li in ion implanted ZnO depends on the preferential localization of the implants, in particular, forming characteristic Li depleted or Li pile-up regions for Zn or O sublattice occupation of the implants due to the corresponding excess generation of Zn and O interstitials in accordance with the so-called "+1 model." However, the present study reveals that conditions for the radiation damage annealing introduce additional complexity into the interpretation of the Li redistribution trends. Specifically, four implants residing predominantly in the Zn-sublattice, but exhibiting different lattice recovery routes, were considered. Analyzing Li redistribution trends in these samples, it is clearly shown that Li behavior depends on the defect annealing kinetics which is a strong function of the implanted fluence and ion species. Thus, Li depleted and Li pile-up regions (or even combinations of the two) were observed and correlated with the defect evolution in the samples. It is discussed how the observed Li redistribution trends can be used for better understanding a thermal evolution of point defects in ZnO and, in particular, energetics and migration properties of Zn interstitials.
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| 14. |
- Azarov, Alexander, et al.
(författare)
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Dopant incorporation in thin strained Si layers implanted with Sb
- 2010
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Ingår i: Thin Solid Films. - : Elsevier BV. - 0040-6090 .- 1879-2731. ; 518:9, s. 2474-2477
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Tidskriftsartikel (refereegranskat)abstract
- The effect of tensile strain on Sb incorporation in Si and its activation during post-implantation annealing has been Studied by a combination of Rutherford backscattering/channeling spectrometry, secondary ion mass spectrometry. X-ray diffraction and 4-point probe measurements Our results show that, for Sb implanted samples a tensile strain has an important role for dopant behavior Particularly, increasing the tensile strain in the Si layer from 0 to 0 8% leads to an enhancement of the fraction of incorporated Sb atoms in substitutional sites already during implantation from similar to 7 to 30% Furthermore, 0 8% strain in antimony doped Si gives similar to 20% reduction in the sheet resistance in comparison to the unstrained sample.
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| 15. |
- Bathen, M. E., et al.
(författare)
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Anisotropic and plane-selective migration of the carbon vacancy in SiC : Theory and experiment
- 2019
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Ingår i: Physical Review B. - : American Physical Society. - 2469-9950 .- 2469-9969. ; 100:1
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the migration mechanism of the carbon vacancy (VC) in silicon carbide (SiC) using a combination of theoretical and experimental methodologies. The VC, commonly present even in state-of-the-art epitaxial SiC material, is known to be a carrier lifetime killer and therefore strongly detrimental to device performance. The desire for VC removal has prompted extensive investigations involving its stability and reactivity. Despite suggestions from theory that VC migrates exclusively on the C sublattice via vacancy-atom exchange, experimental support for such a picture is still unavailable. Moreover, the existence of two inequivalent locations for the vacancy in 4H-SiC [hexagonal, VC(h), and pseudocubic, VC(k)] and their consequences for VC migration have not been considered so far. The first part of the paper presents a theoretical study of VC migration in 3C- and 4H-SiC. We employ a combination of nudged elastic band (NEB) and dimer methods to identify the migration mechanisms, transition state geometries, and respective energy barriers for VC migration. In 3C-SiC, VC is found to migrate with an activation energy of EA=4.0 eV. In 4H-SiC, on the other hand, we anticipate that VC migration is both anisotropic and basal-plane selective. The consequence of these effects is a slower diffusivity along the axial direction, with a predicted activation energy of EA=4.2 eV, and a striking preference for basal migration within the h plane with a barrier of EA=3.7 eV, to the detriment of the k-basal plane. Both effects are rationalized in terms of coordination and bond angle changes near the transition state. In the second part, we provide experimental data that corroborates the above theoretical picture. Anisotropic migration of VC in 4H-SiC is demonstrated by deep level transient spectroscopy (DLTS) depth profiling of the Z1/2 electron trap in annealed samples that were subject to ion implantation. Activation energies of EA=(4.4±0.3) eV and EA=(3.6±0.3) eV were found for VC migration along the c and a directions, respectively, in excellent agreement with the analogous theoretical values. The corresponding prefactors of D0=0.54cm2/s and 0.017cm2/s are in line with a simple jump process, as expected for a primary vacancy point defect.
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| 16. |
- Bathen, M. E., et al.
(författare)
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Influence of carbon cap on self-diffusion in silicon carbide
- 2020
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Ingår i: Crystals. - : MDPI AG. - 2073-4352. ; 10:9, s. 1-11
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Tidskriftsartikel (refereegranskat)abstract
- Self-diffusion of carbon (12C and13C) and silicon (28Si and30Si) in 4H silicon carbide has been investigated by utilizing a structure containing an isotope purified 4H-28Si12C epitaxial layer grown on an n-type (0001) 4H-SiC substrate, and finally covered by a carbon capping layer (C-cap). The13C and30Si isotope profiles were monitored using secondary ion mass spectrometry (SIMS) following successive heat treatments performed at 2300–2450◦C in Ar atmosphere using an inductively heated furnace. The30Si profiles show little redistribution within the studied temperature range, with the extracted diffusion lengths for Si being within the error bar for surface roughening during annealing, as determined by profilometer measurements. On the other hand, a significant diffusion of13C was observed into the isotope purified layer from both the substrate and the C-cap. A diffusivity of D = 8.3 × 106 e−10.4/kBT cm2/s for13C was extracted, in contrast to previous findings that yielded lower both pre-factors and activation energies for C self-diffusion in SiC. The discrepancy between the present measurements and previous theoretical and experimental works is ascribed to the presence of the C-cap, which is responsible for continuous injection of C interstitials during annealing, and thereby suppressing the vacancy mediated diffusion.
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| 17. |
- Diaz, Matias R., et al.
(författare)
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TOI-132 b: A short-period planet in the Neptune desert transiting a V=11.3 G-type star
- 2020
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 493:1, s. 973-985
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Tidskriftsartikel (refereegranskat)abstract
- The Neptune desert is a feature seen in the radius-period plane, whereby a notable dearth of short period, Neptune-like planets is found. Here, we report the Transiting Exoplanet Survey Satellite (TESS) discovery of a new short-period planet in the Neptune desert, orbiting the G-type dwarf TYC 8003-1117-1 (TOI-132). TESS photometry shows transit-like dips at the level of similar to 1400 ppm occurring every similar to 2.11 d. High-precision radial velocity follow-up with High Accuracy Radial Velocity Planet Searcher confirmed the planetary nature of the transit signal and provided a semi-amplitude radial velocity variation of 11.38(-0.85)(+0.84) m s(-1), which, when combined with the stellar mass of 0.97 +/- 0.06 M-circle dot, provides a planetary mass of 22.40(-1.92)(+1.90) M-circle plus. Modelling the TESS light curve returns a planet radius of 3.42(-0.14)(+0.13) R-circle plus , and therefore the planet bulk density is found to be 3.08(-0.46)(+0.44) g cm(-3). Planet structure models suggest that the bulk of the planet mass is in the form of a rocky core, with an atmospheric mass fraction of 4.3(-2.3)(+1.2) percent. TOI-132 b is a TESS Level 1 Science Requirement candidate, and therefore priority follow-up will allow the search for additional planets in the system, whilst helping to constrain low-mass planet formation and evolution models, particularly valuable for better understanding of the Neptune desert.
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| 18. |
- Gogova, D., et al.
(författare)
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High crystalline quality homoepitaxial Si-doped β-Ga2O3(010) layers with reduced structural anisotropy grown by hot-wall MOCVD
- 2024
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Ingår i: Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films. - 0734-2101. ; 42:2
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Tidskriftsartikel (refereegranskat)abstract
- A new growth approach, based on the hot-wall metalorganic chemical vapor deposition concept, is developed for high-quality homoepitaxial growth of Si-doped single-crystalline β -Ga 2 O 3 layers on (010)-oriented native substrates. Substrate annealing in argon atmosphere for 1 min at temperatures below 600 ° C is proposed for the formation of epi-ready surfaces as a cost-effective alternative to the traditionally employed annealing process in oxygen-containing atmosphere with a time duration of 1 h at about 1000 ° C. It is shown that the on-axis rocking curve widths exhibit anisotropic dependence on the azimuth angle with minima for in-plane direction parallel to the [001] and maximum for the [100] for both substrate and layer. The homoepitaxial layers are demonstrated to have excellent structural properties with a β -Ga 2 O 3 (020) rocking curve full-widths at half-maximum as low as 11 arc sec, which is lower than the corresponding one for the substrates (19 arc sec), even for highly Si-doped (low 10 19 cm − 3 range) layers. Furthermore, the structural anisotropy in the layer is substantially reduced with respect to the substrate. Very smooth surface morphology of the epilayers with a root mean square roughness value of 0.6 nm over a 5 × 5 μ m 2 area is achieved along with a high electron mobility of 69 cm 2 V − 1 s − 1 at a free carrier concentration n = 1.9 × 10 19 cm − 3 . These values compare well with state-of-the-art parameters reported in the literature for β -Ga 2 O 3 (010) homoepitaxial layers with respective Si doping levels. Thermal conductivity of 17.4 W m − 1 K − 1 is determined along the [010] direction for the homoepitaxial layers at 300 K, which approaches the respective value of bulk crystal (20.6 W m − 1 K − 1 ). This result is explained by a weak boundary effect and a low dislocation density in the homoepitaxial layers.
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| 19. |
- Grini, S., et al.
(författare)
-
Dynamic Impurity Redistributions in Kesterite Absorbers
- 2020
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Ingår i: Physica status solidi. B, Basic research. - : Wiley. - 0370-1972 .- 1521-3951.
-
Tidskriftsartikel (refereegranskat)abstract
- Cu2ZnSn(S,Se)4 is a promising nontoxic earth-abundant solar cell absorber. To optimize the thin films for solar cell device performance, postdeposition treatments at temperatures below the crystallization temperature are normally performed, which alter the surface and bulk properties. The polycrystalline thin films contain relatively high concentrations of impurities, such as sodium, oxygen and hydrogen. During the treatments, these impurities migrate and likely agglomerate at lattice defects or interfaces. Herein, impurity redistribution after air annealing for temperatures up to 200 °C and short heavy water treatments are studied. In addition, nonuniformities of the sodium distribution on a nanometer and micrometer scale are characterized by atom probe tomography and secondary ion mass spectrometry, respectively. Sodium and oxygen correlate to a greater extent after heat treatments, supporting strong binding between the two impurities. Redistributions of these impurities occur even at room temperature over longer time periods. Heavy water treatments confirm out-diffusion of sodium with more incorporation of oxygen and hydrogen. It is observed that the increased hydrogen content does not originate from the heavy water. The existence of an “ice-like” layer on top of the Cu2ZnSnS4 layer is proposed.
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| 20. |
- Khranovskyy, Volodymyr, et al.
(författare)
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Complementary study of the photoluminescence and electrical properties of ZnO films grown on 4H-SiC substrates
- 2017
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Ingår i: Journal of Luminescence. - : ELSEVIER SCIENCE BV. - 0022-2313 .- 1872-7883. ; 181, s. 374-381
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Tidskriftsartikel (refereegranskat)abstract
- We have studied the photoluminescence and electrical properties of ZnO films grown epitaxially by atmospheric pressure MOCVD on 4H-SiC substrates. The dominating DA line on the low temperature PL spectrum is attributed to the emission of an exciton bound to the neutral donor. The intensity of this line correlates with the electrical properties of the films: the decrease of DA intensity occurs simultaneously with the increase of the carriers mobility. This we explain as donor activation providing free electrons to the conduction band. Based on the comparison of the calculated value of donor binding energy, the literature data and complementary SIMS analysis a suggested donor impurity is aluminum (Al). The exciton localization energy is 16.3 meV, and agrees well with localization energy of 15.3 meV for Al impurity reported by other authors (e.g. Ref. [33]). The thermal activation energy E-D=22 meV, determined from the Hall data and is in agreement with the optical activation energy 20 meV, which is derived from the temperature-dependent PL study. The calculated value of the donor binding energy of 54.3 eV is in agreement with the ionization energy of 53 meV mentioned in earlier reports for Al in ZnO films. Our results prove that the commonly observed line at similar to 3.3599 eV on low temperature PL spectra of ZnO is a neutral donor bound exciton emission due to the Al impurity. (C) 2016 Elsevier B.V. All rights reserved.
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| 21. |
- Li, Yu-Xuan, et al.
(författare)
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Quantification of Cold-Ion Beams in a Magnetic Reconnection Jet
- 2021
-
Ingår i: Frontiers in Astronomy and Space Sciences. - : Frontiers Media S.A.. - 2296-987X. ; 8
-
Tidskriftsartikel (refereegranskat)abstract
- Cold (few eV) ions of ionospheric origin are widely observed in the lobe region of Earth's magnetotail and can enter the ion jet region after magnetic reconnection is triggered in the magnetotail. Here, we investigate a magnetotail crossing with cold ions in one tailward and two earthward ion jets observed by the Magnetospheric Multiscale (MMS) constellation of spacecraft. Cold ions co-existing with hot plasma-sheet ions form types of ion velocity distribution functions (VDFs) in the three jets. In one earthward jet, MMS observe cold-ion beams with large velocities parallel to the magnetic fields, and we perform quantitative analysis on the ion VDFs in this jet. The cold ions, together with the hot ions, are reconnection outflow ions and are a minor population in terms of number density inside this jet. The average bulk speed of the cold-ion beams is approximately 38% larger than that of the hot plasma-sheet ions. The cold-ion beams inside the explored jet are about one order of magnitude colder than the hot plasma-sheet ions. These cold-ion beams could be accelerated by the Hall electric field in the cold ion diffusion region and the shrinking magnetic field lines through the Fermi effect.
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| 22. |
- Linnarsson, Margareta, et al.
(författare)
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Influence of a thin amorthous layer on de-channeling during aluminum implantation at different temperatures into 4H-SiC
- 2019
-
Ingår i: Applied Physics A. - : Springer Berlin/Heidelberg. - 0947-8396 .- 1432-0630. ; 125:12
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Tidskriftsartikel (refereegranskat)abstract
- Ion implantation is an important technique in semiconductor processing and has become a key technology for 4H-SiC devices. Today, aluminum (Al) implantations are routinely used for p-type contacts, p(+)-emitters, terminations and many other applications. However, in all crystalline materials, quite a few ions find a path along a crystal channel, so-called channeling, and these ions travel deep into the crystal. This paper reports on the channeling phenomenon during Al implantation into 4H-SiC, and in particular, the influence of a thin native oxide will be discussed in detail. The effects of thermal lattice vibrations for implantations performed at elevated temperatures will also be elucidated. 100 keV Al ions have been implanted along the [000-1] direction employing samples with 4 degrees miscut. Before implantation, the samples have been aligned using the blocking pattern of backscattered protons. Secondary ion mass spectrometry has been used to record the Al depth distribution. To predict implantation profiles and improve understanding of the role of crystal structure, simulations were performed using the Monte-Carlo binary collision approximation code SIIMPL. Our results show that a thin surface layer of native oxide, less than 1 nm, has a decisive role for de-channeling of aligned implantations. Further, as expected, for implantations at elevated temperatures, a larger degree of de-channeling from major axes is present due to increased thermal vibrations and the penetration depth of channeled aluminum ions is reduced. The values for the mean-square atomic displacements at elevated temperatures have been extracted from experimental depth profiles in combination with simulations.
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| 23. |
- Linnarsson, Margareta, et al.
(författare)
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Intentional and unintentional channeling during implantation of 51V ions into 4H-SiC
- 2019
-
Ingår i: Semiconductor Science and Technology. - : IOP Publishing. - 0268-1242 .- 1361-6641. ; 34, s. 1-10
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Tidskriftsartikel (refereegranskat)abstract
- Ion implantation is a commonly used process step in 4H-SiC device manufacturing to implement precise concentrations of dopant atoms in selected areas and depths. This paper reports on vanadium (V) implantation into 4H-SiC(0001) and how the crystal lattice, with preferential directions, channels, for the ions, will influence the final dopant distribution. Concentration versus depth profiles of V-ions, intentionally and unintentionally channelled, has been recorded by secondary ion mass spectrometry. Ion implantations have been performed between 50 and 300 keV at various impact angles and fluence at room temperature as well as at elevated temperatures. Before ion implantation, the samples were aligned utilizing the blocking pattern of 100 keV backscattered protons. In addition to the aligned implantations, our standard beam line for ion implantation has been used for implantations in a 'random' direction using the wafer miscut angle of 4 degrees. The electronic stopping has been determined from these 'random' cases and the values have been used in 3D simulations to predict preferential crystallographic directions using SIIMPL, a Monte Carlo simulation code based on the binary collision approximation. The results show that, independent of the used impact angle there is always a probability that the vanadium ions will be steered into the [000-1] and the family of < 11-2-3 > crystal directions and therefore penetrate deep into the sample, resulting in unwanted 'spikes'. If the implantation is performed at elevated temperatures, a larger degree of dechanneling is present due to increased thermal vibrations and the penetration depth of vanadium is slightly reduced.
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| 24. |
- Linnarsson, Margareta K., et al.
(författare)
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Alkali metal re-distribution after oxidation of 4H-SiC
- 2016
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Ingår i: 16th International Conference on Silicon Carbide and Related Materials, ICSCRM 2015. - : Trans Tech Publications Ltd. - 9783035710427 ; , s. 677-680
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Konferensbidrag (refereegranskat)abstract
- Relocation of alkali metals sodium, potassium and cesium during oxidation of 4H-SiC has been studied by secondary ion mass spectrometry. The alkali metal source has been introduced by ion implantation before oxidation into n- and p-type 4H-SiC samples. Dry oxidation of SiC has been performed at 1150 ºC during 4, 8 and 16 h. In the formed oxide, the main part of the alkali metals diffuses out via the SiO2 surface. Close to the moving SiO2/SiC interface, a minor amount of alkali metals is retained. In the SiC material, the main amount of implanted alkali atoms is not redistributed during the oxidation, although a minor amount diffuses deeper into the samples. For ptype 4H-SiC, the diffusion deeper into the samples of the studied alkali metals decreases as the mass increases, Na+<K+<Cs+, but the sodium mobility is substantial already at 1150 °C.
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| 25. |
- Linnarsson, Margareta K., et al.
(författare)
-
Influence from the electronic shell structure on the range distribution during channeling of 40-300 keV ions in 4H-SiC
- 2021
-
Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 130:7
-
Tidskriftsartikel (refereegranskat)abstract
- Ion implantation is performed in H-4-SiC with B-11, Al-27, P-31, V-51, Ga-71, and As-75 ions using energies between 40 and 300 keV at various fluences along the [000-1] or the < 11-2-3 > axes. Secondary ion mass spectrometry is utilized to determine the depth distribution of the implanted elements. A Monte Carlo binary collision approximation (MC-BCA) code for crystalline targets is then applied to explain the influence of the electronic shell structure on electronic stopping and the obtained channeled ion depth distributions. The results show that, as the atomic number increases in a row of the periodic table, i.e., as the ionic radius decreases and the electron clouds densify, the interaction with the target electrons increases and the range is reduced. The decreased range is particularly pronounced going from Al-27 to P-31. The reduction in channeling depth is discussed in terms of electronic shells and can be related to the ionic radii, as defined by Kohn-Sham. It is shown that these shell effects in channeled implantations can easily be included in MC-BCA simulations simply by modifying the screening length used in the local treatment of electronic stopping in channels. However, it is also shown that, for vanadium ions with an unfilled d-shell, this simple model is insufficient to predict the electronic stopping in the channels.
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| 26. |
- Linnarsson, Margareta K., et al.
(författare)
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Surface erosion of ion-implanted 4H-SiC during annealing with carbon cap
- 2018
-
Ingår i: International Conference on Silicon Carbide and Related Materials, ICSCRM 2017. - : Trans Tech Publications Inc.. - 9783035711455 ; , s. 373-376
-
Konferensbidrag (refereegranskat)abstract
- The stability/ erosion of the interface between a C-cap and 4H-SiC have been studied by secondary ion mass spectrometry (SIMS). Aluminum implantation has been used to monitor the position of the moving interface as well as to investigate the influence on the interface stability by the crystal quality of the 4H-SiC. After Al implantation a C-cap has been deposited by pyrolysis of photoresist. Subsequent annealing has been performed at 1900 and 2000 °C with durations between 15 minutes and 1 hour. SIMS measurements have been performed without removal of the C-cap. The surface remains smooth after the heat treatment, but a large amount of SiC material from the uppermost part of the wafer is lost. The amount of lost material is related to for instance annealing temperature, ambient conditions and ion induced crystal damage. This contribution gives a brief account of the processes governing the SiC surface decomposition during C-cap post implant annealing.
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| 27. |
- Neuvonen, P. T., et al.
(författare)
-
Transportation of Na and Li in hydrothermally grown ZnO
- 2010
-
Ingår i: Zinc oxide and related materials 2009. - : Materials Research Society. - 9781605111742 ; , s. 29-34
-
Konferensbidrag (refereegranskat)abstract
- Secondary ion mass spectrometry has been applied to study the transportation of Na and Li in hydrothermally grown ZnO. A dose of 10 15 cm-2 of Na+ was implanted into ZnO to act as a diffusion source. A clear trap limited diffusion is observed at temperatures above 550 °C. From these profiles, an activation energy for the transport of Na of 7 ∼1.7 eV has been extracted. The prefactor for the diffusion constant and the solid solubility of Na cannot be deduced independently from the present data but their product estimated to be ∼ 3 × 1016 cm-1 s-1. A dissociation energy of ∼2.4 eV is extracted for the trapped Na. The measured Na and Li profiles show that Li and Na compete for the same traps and interact in a way that Li is depleted from Na-rich regions. This is attributed to a lower formation energy of Na-on-zinc-site than that for Li-on-zinc-site defects and the zinc vacancy is considered as a major trap for migrating Na and Li atoms. Consequently, the diffasivity of Li is difficult to extract accurately from the present data, but in its interstitial configuration Li is indeed highly mobile having a diffasivity in excess of 10-11 cm2 s-1 at 500 °C .
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| 28. |
- Olsen, V. S., et al.
(författare)
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Evidence of defect band mechanism responsible for band gap evolution in (ZnO)(1-x)(GaN)(x) alloys
- 2019
-
Ingår i: Physical Review B. - : AMER PHYSICAL SOC. - 2469-9950 .- 2469-9969. ; 100:16
-
Tidskriftsartikel (refereegranskat)abstract
- It is known that (ZnO)(1-x)(GaN)(x) alloys demonstrate remarkable energy band bowing, making the material absorb in the visible range, in spite of the binary components being classical wide band gap semiconductors. However, the origin of this bowing is not settled; two major mechanisms are under debate: Influence of the orbital repulsion and/or formation of a defect band. In the present work, we applied a combination of the absorption and emission measurements on the samples exhibiting an outstanding nanoscale level of (ZnO)(1-x)(GaN)(x) homogeneity as monitored by the high resolution electron microscopy equipped with the energy dispersive x-ray analysis and the electron energy loss spectroscopy; moreover the experimental data were set in the context of the computational analysis of the alloys employing density functional theory and quasiparticle GW approximation. A prominent discrepancy in the band gap values as deduced from the absorption and emission experiments was observed systematically for the alloys with different compositions and interpreted as evidence for the absorption gap shrinking due to the defect band formation. Computational data support the argument, revealing only minor variations in the bulk of the conduction and valence band structures of the alloys, except for a characteristic "tail" in the vicinity of the valence band maximum. As such, we conclude that the energy gap bowing in (ZnO)(1-x)(GaN)(x) alloys is due to the defect band formation, presumably at the top of the valence band maximum.
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| 29. |
- Ross, N., et al.
(författare)
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Cu2ZnSn(S,Se)4 Solar Cell Absorbers from Diffusion of Selenium into Annealed Cu2ZnSnS4 Absorbers
- 2016
-
Ingår i: 2016 IEEE 43rd Photovoltaic Specialists Conference (PVSC). - New York : IEEE. - 9781509027248 ; , s. 492-497
-
Konferensbidrag (refereegranskat)abstract
- Small grain compound-sputtered Copper Zinc Tin Sulfide (CZTS) precursors and large grain recrystallized CZTS solar cell absorbers are annealed at sub-recrystallization temperatures in selenium atmosphere to promote selenium diffusion into the CZTS films. Grazing incidence x-ray diffraction and Raman spectroscopy show the presence of two distinct sulfide and mixed sulfide/selenide phases, with the selenide-like phase more prominent at the front surface of the absorber. Only a narrow range of sulfur-to-selenium ratios is observed in the sulfide/selenide phase. Secondary ion mass spectrometry profiles show a compositional sulfur-selenium gradient for samples annealed at 450 degrees C. Scanning electron microscopy with energy dispersive X-ray spectroscopy reveals that the compositional gradient is formed by a spatial distribution of sulfide/selenide grains, embedded in the remaining sulfide absorber. Sulfur-selenium gradients within single absorber grains are not observed, indicating that the mixed sulfide/selenide phase nucleates and grows in competition with the existing sulfide phase, rather than forming by replacement of anions within existing crystals. IV and EQE measurements of devices fabricated from the selenized absorbers support this conclusion.
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| 30. |
- Ross, N., et al.
(författare)
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Mixed sulfur and selenium annealing study of compound-sputtered bilayer Cu2ZnSnS4 / Cu2ZnSnSe4 precursors
- 2017
-
Ingår i: 2017 IEEE 44Th Photovoltaic Specialist Conference (PVSC). - : IEEE. - 9781509056057 ; , s. 3269-3274
-
Konferensbidrag (refereegranskat)abstract
- Copper zinc tin sulfide (CZTS) and copper zinc tin selenide (CZTSe) precursor films are compound co-sputtered from metal sulfide and selenide targets. A bilayer precursor consisting of a CZTS-only underlayer and CZTSe-only overlayer is also sputtered. These precursor films are annealed with varying ratios of elemental sulfur and selenium to promote the formation of recrystallized Cu2ZnSn(S, Se) 4 (CZTSSe) solar cell absorber layers with intermediate sulfur-to-selenium ratios Sr=[S]/([S]+[Se]). The films are characterized by scanning electron microscope (SEM) energy dispersive X-ray spectroscopy (EDX), secondary ion mass spectrometry (SIMS), and grazingincidence X-ray diffraction (GIXRD). Selenium-containing precursors produce absorber layers with rougher surfaces, leading to higher short-circuit currents Jsc for some annealing conditions. The Sr value of the crystallized absorber is independent of the ratio of sulfur to selenium in the precursor unless sulfur is deficient in the anneal. Sulfur-selenium distribution in bilayer precursors after mixed S/Se annealing is found to be uniform: neither a step nor significant sulfur-gradient remains. We relate the chalcogen distribution after annealing to the excess of chalcogen in the anneal, and discuss the consequences for back-grading of the band gap by sulfur-selenium variation. Both the thickness and Sr value of the Mo(S, Se) 2 back contact is found to be dependent on the sulfur-selenium ratio of the precursor, with CZTSe precursors producing thicker and more selenium rich back contact layers.
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| 31. |
- Ross, Nils, et al.
(författare)
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Practical limitations to selenium annealing of compound co-sputtered Cu2ZnSnS4 as a route to achieving sulfur-selenium graded solar cell absorbers
- 2017
-
Ingår i: Thin Solid Films. - : ELSEVIER SCIENCE SA. - 0040-6090 .- 1879-2731. ; 623, s. 110-115
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Tidskriftsartikel (refereegranskat)abstract
- The suitability of selenium annealing as a technique to introduce energy band gap gradients via sulfur selenium substitution in Cu2ZnSnS4 (CZTS) films is evaluated. Compound co-sputtered CZTS precursors are annealed in selenium atmosphere at 425 degrees C, either as-deposited or after a short time sulfur pre-anneal. The films are investigated by Raman spectroscopy and X-ray diffractometry, and the spatial distribution of elemental species measured by secondary ion mass spectrometry and energy dispersive X-ray spectroscopy. Sulfur-selenium gradients are not achieved for the as-deposited precursor. Sulfur-selenium gradients are achieved in the early stages of annealing for pre-anneal samples, where Cu2ZnSn(S,Se)(4) (CZTSSe) formation is found to be correlated spatially with sodium distribution. These gradients are lost as the annealing progresses. Selenisation occurs by CZTSSe grain growth, rather than by direct substitution of selenium for sulfur. The spatial correlation of high sodium concentration with CZTSSe formation suggests that liquid phase sodium selenide facilitates selenium incorporation during recrystallisation, limiting the practicality of anion-grading of CZTSSe during the annealing step as a means of establishing a graded band gap.
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| 32. |
- Schulz, Robert, et al.
(författare)
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Is the future of peer review automated?
- 2022
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Ingår i: BMC Research Notes. - : Springer Nature. - 1756-0500. ; 15:1
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The rising rate of preprints and publications, combined with persistent inadequate reporting practices and problems with study design and execution, have strained the traditional peer review system. Automated screening tools could potentially enhance peer review by helping authors, journal editors, and reviewers to identify beneficial practices and common problems in preprints or submitted manuscripts. Tools can screen many papers quickly, and may be particularly helpful in assessing compliance with journal policies and with straightforward items in reporting guidelines. However, existing tools cannot understand or interpret the paper in the context of the scientific literature. Tools cannot yet determine whether the methods used are suitable to answer the research question, or whether the data support the authors' conclusions. Editors and peer reviewers are essential for assessing journal fit and the overall quality of a paper, including the experimental design, the soundness of the study's conclusions, potential impact and innovation. Automated screening tools cannot replace peer review, but may aid authors, reviewers, and editors in improving scientific papers. Strategies for responsible use of automated tools in peer review may include setting performance criteria for tools, transparently reporting tool performance and use, and training users to interpret reports.
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| 33. |
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| 34. |
- Stehr, Jan Eric, et al.
(författare)
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Zinc-Vacancy–Donor Complex : A Crucial Compensating Acceptor in ZnO
- 2014
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Ingår i: Physical Review Applied. - : American Physical Society. - 2331-7019. ; 2:021001
-
Tidskriftsartikel (refereegranskat)abstract
- The aluminum–zinc-vacancy (Al Zn −V Zn ) complex is identified as one of the dominant defects in Al-containing n -type ZnO after electron irradiation at room temperature with energies above 0.8 MeV. The complex is energetically favorable over the isolated V Zn , binding more than 90% of the stable V Zn ’s generated by the irradiation. It acts as a deep acceptor with the (0/− ) energy level located at approximately 1 eV above the valence band. Such a complex is concluded to be a defect of crucial and general importance that limits the n -type doping efficiency by complex formation with donors, thereby literally removing the donors, as well as by charge compensation.
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| 35. |
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| 36. |
- Toledo-Redondo, S., et al.
(författare)
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Impacts of Ionospheric Ions on Magnetic Reconnection and Earth's Magnetosphere Dynamics
- 2021
-
Ingår i: Reviews of geophysics. - : John Wiley & Sons. - 8755-1209 .- 1944-9208. ; 59:3
-
Forskningsöversikt (refereegranskat)abstract
- Ionospheric ions (mainly H+, He+, and O+) escape from the ionosphere and populate the Earth's magnetosphere. Their thermal energies are usually low when they first escape the ionosphere, typically a few electron volt to tens of electron volt, but they are energized in their journey through the magnetosphere. The ionospheric population is variable, and it makes significant contributions to the magnetospheric mass density in key regions where magnetic reconnection is at work. Solar wind—magnetosphere coupling occurs primarily via magnetic reconnection, a key plasma process that enables transfer of mass and energy into the near-Earth space environment. Reconnection leads to the triggering of magnetospheric storms, auroras, energetic particle precipitation and a host of other magnetospheric phenomena. Several works in the last decades have attempted to statistically quantify the amount of ionospheric plasma supplied to the magnetosphere, including the two key regions where magnetic reconnection occurs: the dayside magnetopause and the magnetotail. Recent in situ observations by the Magnetospheric Multiscale spacecraft and associated modeling have advanced our current understanding of how ionospheric ions alter the magnetic reconnection process, including its onset and efficiency. This article compiles the current understanding of the ionospheric plasma supply to the magnetosphere. It reviews both the quantification of these sources and their effects on the process of magnetic reconnection. It also provides a global description of how the ionospheric ion contribution modifies the way the solar wind couples to the Earth's magnetosphere and how these ions modify the global dynamics of the near-Earth space environment.Plain Language SummaryAbove the neutral atmosphere, space is filled with charged particles, which are tied to the Earth's magnetic field. The particles come from two sources, the solar wind and the Earth's upper atmosphere. Most of the solar wind particles are deflected by the Earth´s magnetic field, but some can penetrate into near-Earth space. The ionized layer of the upper atmosphere is continuously ejecting particles into space, which have low energies and are difficult to measure. We investigate the relative importance of the two charged particle sources for the dynamics of plasma processes in near-Earth space. In particular, we consider the effects of these sources in magnetic reconnection. Magnetic reconnection allows initially separated plasma regions to become magnetically connected and mix, and converts magnetic energy to kinetic energy of charged particles. Magnetic reconnection is the main driver of geomagnetic activity in the near-Earth space, and is responsible for the release of energy that drives a variety of space weather effects. We highlight the fact that plasma from the ionized upper atmosphere contributes a significant part of the density in the key regions where magnetic reconnection is at work, and that this contribution is larger when the geomagnetic activity is high.
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| 37. |
- Toombs, A. L., et al.
(författare)
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Supporting the complex social lives of new parents
- 2018
-
Ingår i: CHI '18 Proceedings of the 2018 CHI Conference on Human Factors in Computing Systems. - New York, NY, USA : Association for Computing Machinery (ACM). - 9781450356206 - 9781450356213
-
Konferensbidrag (refereegranskat)abstract
- One of the many challenges of becoming a parent is the shift in one's social life. As HCI researchers have begun to investigate the intersection of sociotechnical system design and parenthood, they have also sought to understand how parents' social lives can be best supported. We build on these strands of research through a qualitative study with new parents regarding the role of digital technologies in their social lives as they transition to parenthood. We demonstrate how sociotechnical systems are entangled in the ways new parents manage their relationships, build (or resist building) new friendships and ad hoc support systems, and navigate the vulnerabilities of parenthood. We discuss how systems designed for new parents can better support the vulnerabilities they internalize, the diverse friendships they desire, and the logistical challenges they experience. We conclude with recommendations for future design and research in this area.
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| 38. |
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| 39. |
- Vines, L, et al.
(författare)
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Effect spatial defect distribution on the electrical behavior of prominent vacancy points defects in swift-ion implanted Si
- 2009
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 79:7, s. 075206-
-
Tidskriftsartikel (refereegranskat)abstract
- Samples of epitaxially grown n-type silicon have been implanted at room temperature with low doses (10(6)-10(9) cm(-2)) of He, C, Si, and I ions using energies from 2.75 to 46 MeV. Deep level transient spectroscopy studies reveal that the generation of divacancy (V-2) and vacancy-oxygen (VO) pairs has a distinct ion mass dependence. Especially, the doubly negative charge state of the divacancy, V-2(=/-), decreases in intensity with increasing ion mass compared to that of the singly negative charge state of the divacancy, V-2(-/0). In addition, the measurements show also a decrease in the intensity of the level assigned to VO compared to that of V-2(-/0) with increasing ion mass. Carrier capture cross-section measurements demonstrate a reduction in the electron capture rate with increasing ion mass for all the three levels V-2(-/0), V-2(=/-), and VO; but a gradual recovery occurs with annealing. Concurrently, the strength of the V-2(-/0) level decreases in a wide temperature range starting from below 200 degrees C, accompanied by an increase in the amplitudes of both the VO and V-2(=/-) peaks. In order to account for these results a model is introduced where local carrier compensation is a key feature and where two modes of V-2 are considered: (1) V-2 centers located in regions with a high defect density around the ion track (V-2(dense)) and (2) V-2 centers located in regions with a low defect density (V-2(dilute)). The V-2(dense) fraction does not give any contribution to the V-2(=/-) signal due to local carrier compensation, and the amplitude of the V-2(=/-) level is determined by the V-2(dilute) fraction only. The spatial distributions of defects generated by single-ion impacts were simulated by Monte Carlo calculations in the binary collision approximation, and to distinguish between the regions with V-2(dense) and V-2(dilute) a threshold for the defect generation rate was introduced. The model is shown to give good quantitative agreement with the experimentally observed ion mass dependence for the ratio between the amplitudes of the V-2(=/-) and V-2(-/0) peaks. In particular, the threshold value for the defect generation rate remains constant (similar to 1.2 vacancies/ion/A) irrespective of the type of ion used, which provides strong evidence for the validity of the model. Annealing at temperatures above similar to 300 degrees C is found to reduce the spatial localization of the defects and migration of V-2 occurs with subsequent trapping by interstitial oxygen atoms and formation of divacancy-oxygen pairs.
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| 40. |
- Vines, L, et al.
(författare)
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Formation and annealing behavior of prominent point defects in MeV ion implanted n-type epitaxial Si
- 2009
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Ingår i: Materials Science & Engineering. - : Elsevier BV. - 0921-5107 .- 1873-4944. ; 159-160, s. 177-181
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Tidskriftsartikel (refereegranskat)abstract
- Samples of epitaxially grown n-type Si have been implanted with low doses (< 1 x 10(9) cm(-1)) of He, C, Si, and I ions using energies from 2.75 to 48 MeV. Deep level transient spectroscopy (DLTS) analysis of the implanted samples reveals a stronger signal for the signature of the singly negative charge state of the divacancy (V-2(-/0)) as compared to that of the doubly negative charge state of the divacancy (V-2(=/-)). Isochronal annealing for 20 min ranging from 150 to 400 degrees C results in a gradual decrease ill the DLTS peak amplitude of the V-2(-/0) signature, accompanied by an increase in the peak amplitudes of both the vacancy oxygen pair (VO) and the V-2(=/-) levels, as well as an increase in the carrier Capture rates for the levels. A model based on local compensation of charge carriers front individual ion tracks is proposed in order to explain the results, involving two fractions of V-2: (1) V-2 centers localized in regions with high defect density around the ion track (V-2(dense)) and (2) V-2 centers located in regions with a low defect density (V-2(dilute)).
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| 41. |
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| 42. |
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| 43. |
- Vines, L., et al.
(författare)
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Scanning probe microscopy of single Au ion implants in Si
- 2006
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Ingår i: Materials science & engineering. C, biomimetic materials, sensors and systems. - : Elsevier BV. - 0928-4931 .- 1873-0191. ; 26:07-maj, s. 782-787
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Tidskriftsartikel (refereegranskat)abstract
- We have studied 5 MeV Au2+ ion implantation with fluences between 7 x 10(7) and 2 x 10(8) cm(-2) in Si by deep level transient spectroscopy (DLTS) and scanning capacitance microscopy (SCM). The DLTS measurements show formation of electrically active defects such as the two negative charge states of the divacancy (V-2(=/-) and V-2(-/0)) and the vacancy-oxygen (VO) center. It is observed that the intensity of the V-2(=/-) peak is lower compared to that of V-2(-/0) by a factor of 5. This has been attributed to a highly localized distribution of the defects along the ion tracks, which results in trapping of the carriers at V-2(-/0) and incomplete occupancy of V-2(=/-). The SCM measurements obtained in a plan view show a random pattern of regions with a reduced SCM signal for the samples implanted with fluence above 2 x 10(8) cm(-2). The reduced SCM signal is attributed to extra charges associated with acceptor states, such as V-2(-/0), formed along the ion tracks in the bulk Si. Indeed, the electron emission rate from the V-2(-/0) state is in the range of 10 kHz at room temperature, which is well below the probing frequency of the SCM measurements, resulting in freezing of electrons at V-2(-/0).
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| 44. |
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| 45. |
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| 46. |
- Vines, L., et al.
(författare)
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Visualization of MeV ion impacts in Si using scanning capacitance microscopy
- 2006
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 73:8
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Tidskriftsartikel (refereegranskat)abstract
- Scanning capacitance microscopy (SCM) of 3 MeV Au2+ ion implanted Si have been performed for doses between 2x10(8) and 5x10(9) cm(-2). The measurements show a random pattern of reduced SCM signal (charge trapping) correlated with the ion impacts. These features have a lateral dimension of 150-600 nm and reveal a pronounced dose dependence. It is argued that the Fermi level near the impacts and along the ion tracks is modified (pinned) due to deep acceptor states formed by the penetrating ions. Substantial evidence for this argument is provided by SCM images obtained at different temperatures, where a strong correlation is revealed between the probing frequency and the emission rate of the single negative acceptor level of divacancy. To the best of our knowledge, this is a direct observation of signatures for individual ion impacts in Si by an electrical scanning technique.
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| 47. |
- Vines, S. K., et al.
(författare)
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EMIC Waves in the Outer Magnetosphere : Observations of an Off-Equator Source Region
- 2019
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Ingår i: Geophysical Research Letters. - : Blackwell Publishing. - 0094-8276 .- 1944-8007. ; 46:11, s. 5707-5716
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Tidskriftsartikel (refereegranskat)abstract
- Electromagnetic ion cyclotron (EMIC) waves at large L shells were observed away from the magnetic equator by the Magnetospheric MultiScale (MMS) mission nearly continuously for over four hours on 28 October 2015. During this event, the wave Poynting vector direction systematically changed from parallel to the magnetic field (toward the equator), to bidirectional, to antiparallel (away from the equator). These changes coincide with the shift in the location of the minimum in the magnetic field in the southern hemisphere from poleward to equatorward of MMS. The local plasma conditions measured with the EMIC waves also suggest that the outer magnetospheric region sampled during this event was generally unstable to EMIC wave growth. Together, these observations indicate that the bidirectionally propagating wave packets were not a result of reflection at high latitudes but that MMS passed through an off-equator EMIC wave source region associated with the local minimum in the magnetic field.
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| 48. |
- Yakimova, Rositsa, et al.
(författare)
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Growth, defects and doping of 3C-SiC on hexagonal polytypes
- 2017
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Ingår i: ECS Transactions. - : Electrochemical Society. - 9781607685395 ; , s. 107-115, s. 107-115
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Konferensbidrag (refereegranskat)abstract
- Technologies for the growth of 3C-SiC with crystalline quality and crystal size similar to hexagonal counterparts (6H- or 4H-SiC) are still at the laboratory stage. There are several challenges in the control of polytype stability and formation of structural defects which have to be eliminated to reveal the full potential of this material. Nevertheless, 3C-SiC has been explored for various energy, environment and biomedical applications which significantly benefit from the intrinsic semiconductor properties of this material. The future of 3C-SiC and its applications depends on the advances which will be made in improving crystalline quality, enlarging crystal size and controlling doping levels which have not been entirely explored due to the lack of high quality 3C-SiC substrates. This paper reviews recent progress in growth and doping of thick 3C-SiC layers on hexagonal SiC substrates using sublimation epitaxy. It covers the growth process on off-axis substrates and defects occurrence, as well as the issue of obtaining high resistivity material.
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