| 1. |
- Kamiyama, S., et al.
(författare)
-
Extremely high quantum efficiency of donor-acceptor-pair emission in N-and-B-doped 6H-SiC
- 2006
-
Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 99:9
-
Tidskriftsartikel (refereegranskat)abstract
- High-efficiency visible light emission in N-and-B-doped 6H-SiC epilayers was observed in photoluminescence measurements at room temperature. The orange-yellow light emission due to the recombination of donor-acceptor pairs (DAPs) has a broad spectrum with a peak wavelength of 576 nm and a full width at half maximum of 110 nm at 250 K. The high B concentration of more than 1018 cm-3 improves the emission efficiency of the DAP recombination at a high temperature. Compared with the photoluminescence spectrum of GaN at 10 K, a high quantum efficiency of 95% was estimated for the highly B-doped sample. From time-resolved photoluminescence measurements, a DAP recombination time of 5.0 ms was obtained, which is in good agreement with the calculated value by the rate equation with the assumption of a 95% internal quantum efficiency. This is quite promising as a light-emitting medium by optical pumping, as well as monolithic light sources combined with nitride-based light-emitting diodes grown on the DA-doped SiC epilayer. © 2006 American Institute of Physics.
|
|
| 2. |
- Tien Son, Nguyen, et al.
(författare)
-
Negative-U System of Carbon Vacancy in 4H-SiC
- 2012
-
Ingår i: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 109:18, s. 187603-
-
Tidskriftsartikel (refereegranskat)abstract
- Using electron paramagnetic resonance (EPR), energy levels of the carbon vacancy (V-C) in 4H-SiC and its negative-U properties have been determined. Combining EPR and deep-level transient spectroscopy we show that the two most common defects in as-grown 4H-SiC-the Z(1/2) lifetime-limiting defect and the EH7 deep defect-are related to the double acceptor (2 - vertical bar 0) and single donor (0 vertical bar +) levels of V-C, respectively.
|
|
| 3. |
|
|
| 4. |
|
|
| 5. |
|
|
| 6. |
- Trinh, Xuan Thang, et al.
(författare)
-
Identification of the negative carbon vacancy at quasi-cubic site in 4H-SiC by EPR and theoretical calculations
- 2014
-
Ingår i: Silicon Carbide and Related Materials 2013, PTS 1 AND 2. - : Trans Tech Publications Inc.. ; , s. 285-288
-
Konferensbidrag (refereegranskat)abstract
- In freestanding n-type 4H-SiC epilayers irradiated with low-energy (250 keV) electrons at room temperature, the electron paramagnetic resonance (EPR) spectrum of the negative carbon vacancy at the hexagonal site, V-C(-)(h), and a new signal were observed. From the similarity in defect formation and the spin-Hamiltonian parameters of the two defects, the new center is suggested to be the negative C vacancy at the quasi-cubic site, V-C(-)(k). The identification is further supported by hyperfine calculations.
|
|
| 7. |
- Trinh, Xuan Thang, et al.
(författare)
-
Negative-U carbon vacancy in 4H-SiC : Assessment of charge correction schemes and identification of the negative carbon vacancy at the quasicubic site
- 2013
-
Ingår i: Physical Review B. Condensed Matter and Materials Physics. - : American Physical Society. - 1098-0121 .- 1550-235X. ; 88:23, s. 235209-1-235209-13
-
Tidskriftsartikel (refereegranskat)abstract
- The carbon vacancy (VC) has been suggested by different studies to be involved in the Z1/Z2 defect-a carrier lifetime killer in SiC. However, the correlation between the Z1/Z2 deep level with VC is not possible since only the negative carbon vacancy (V−C) at the hexagonal site, V−C(h), with unclear negative-U behaviors was identified by electron paramagnetic resonance (EPR). Using freestanding n-type 4H-SiC epilayers irradiated with low energy (250 keV) electrons at room temperature to introduce mainly VC and defects in the C sublattice, we observed the strong EPR signals of V−C(h) and another S = 1/2 center. Electron paramagnetic resonance experiments show a negative-U behavior of the two centers and their similar symmetry lowering from C3v to C1h at low temperatures. Comparing the 29Si and 13C ligand hyperfine constants observed by EPR and first principles calculations, the new center is identified as V−C(k). The negative-U behavior is further confirmed by large scale density functional theory supercell calculations using different charge correction schemes. The results support the identification of the lifetime limiting Z1/Z2 defect to be related to acceptor states of the carbon vacancy.
|
|
| 8. |
|
|
| 9. |
- Alajbeg, Ivan, et al.
(författare)
-
Intraoralelectrostimulator for xerostomia relief : along-term, multicenter, open-label, uncontrolled, clinical trial
- 2012
-
Ingår i: Oral surgery, oral medicine, oral pathology and oral radiology. - : Elsevier. - 2212-4403 .- 2212-4411. ; 113:6, s. 773-781
-
Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: A previous sham-controlled multinational study demonstrated the short-term efficacy and safety for xerostomia treatment of an intraoral device that delivers electrostimulation to the lingual nerve. The objective of this study was to test the hypothesis that those beneficial effects would be sustained over an 11-month period. STUDY DESIGN: The device was tested on a mixed sample of 94 patients with xerostomia in an open-label, uncontrolled, prospective multicenter trial. Statutory outcome assessments were done at 5th, 8th, and 11th months and analyzed by multiple comparisons. RESULTS: Improvements achieved at month 5 from baseline were sustained throughout the follow-up period for the primary outcome, xerostomia severity, and the secondary outcomes resting whole salivary flow rate, xerostomia frequency, oral discomfort, and difficulties in speech, swallowing, and sleeping. No significant side effects were detected. CONCLUSIONS: The beneficial effects of a removable intraoral electrostimulating device were sustained for an 11-month period.
|
|
| 10. |
- Pälike, Heiko, et al.
(författare)
-
A Cenozoic record of the equatorial Pacific carbonate compensation depth
- 2012
-
Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 488:7413, s. 609-614
-
Tidskriftsartikel (refereegranskat)abstract
- Atmospheric carbon dioxide concentrations and climate are regulated on geological timescales by the balance between carbon input from volcanic and metamorphic outgassing and its removal by weathering feedbacks; these feedbacks involve the erosion of silicate rocks and organic-carbon-bearing rocks. The integrated effect of these processes is reflected in the calcium carbonate compensation depth, which is the oceanic depth at which calcium carbonate is dissolved. Here we present a carbonate accumulation record that covers the past 53 million years from a depth transect in the equatorial Pacific Ocean. The carbonate compensation depth tracks long-term ocean cooling, deepening from 3.0-3.5 kilometres during the early Cenozoic (approximately 55 million years ago) to 4.6 kilometres at present, consistent with an overall Cenozoic increase in weathering. We find large superimposed fluctuations in carbonate compensation depth during the middle and late Eocene. Using Earth system models, we identify changes in weathering and the mode of organic-carbon delivery as two key processes to explain these large-scale Eocene fluctuations of the carbonate compensation depth.
|
|
| 11. |
- Strietzel, Frank P, et al.
(författare)
-
Efficacy and safety of an intraoral electrostimulation device for xerostomia relief : A multicenter randomized trial
- 2011
-
Ingår i: Arthritis and Rheumatism. - : Wiley. - 0004-3591 .- 1529-0131. ; 63:1, s. 180-190
-
Tidskriftsartikel (refereegranskat)abstract
- Objective: The objective of the study was to evaluate the efficacy in treating xerostomia and the safety of an intraoral electrostimulation device, containing stimulating electrodes, an electronic circuit and a power source. The device delivers electrostimulation through the oral mucosa to the lingual nerve, in order to enhance the salivary reflex. Methods: The device was tested on a sample of patients with xerostomia due to Sjögren’s syndrome and other sicca conditions in a prospective randomized multi-center trial consisting of two stages: (I) a double blind, cross-over designed stage to compare the effects of the electrically “active” device with the “sham” device, both used for one month, and (II) a 3- month open label stage to assess the long-term influence of the “active” device. Improvement of xerostomia severity from baseline was the primary outcome. Results: A total of 114 subjects were randomized. In Stage I, “active” device performed better than “sham” for patient-reported xerostomia severity (p<0.002), xerostomia frequency (p<0.05), quality of life impairment (p<0.01) and swallowing difficulty (p<0.02). At the end of Stage II, statistically significant improvements were verified for patient-reported xerostomia severity (p<0.0001), xerostomia frequency (p<0.0001), oral discomfort (p<0.001), speech difficulty (p<0.02) and sleeping difficulty (p<0.001), and for resting salivary flow-rate (p<0.01). Conclusion: Daily use of the device alleviated oral dryness, discomfort and some complications of xerostomia, such as speech and sleeping difficulties, and increased salivary output. The results show a cumulative positive effect of the device over the period of the study, from baseline to the trial’s end.
|
|
| 12. |
|
|
| 13. |
- Wahab, Qamar Ul, et al.
(författare)
-
4H-and 6H-SiC MOSFETs fabricated on sloped sidewalls formed by molten KOH etching
- 2002
-
Ingår i: Materials Science Forum, Vols. 389-393. ; , s. 1215-1218
-
Konferensbidrag (refereegranskat)abstract
- Vertical 4H- and 6H-SiC MOSFETs have been fabricated on sloped sidewalls formed by molten KOH etching, which is expected to be free from the damage onto a channel region caused by a dry etching process. The slope angle could be controlled by adjusting etching temperature, and the anisotropy of inversion channel mobility was investigated. A higher inversion channel mobility and a lower threshold voltage were observed with increasing slope angle of channel region toward (1 (1) over bar 00) or (11 (2) over bar0). The highest mobility was 32 cm(2)/Vs for 6H-SiC, which is relatively high as an inversion channel mobility of UMOSFETs compared to previous works. The dependence of device performance on the slope angle and crystal orientation is discussed.
|
|
| 14. |
- Walsh, Roddy, et al.
(författare)
-
Enhancing rare variant interpretation in inherited arrhythmias through quantitative analysis of consortium disease cohorts and population controls
- 2021
-
Ingår i: Genetics in Medicine. - : Nature Publishing Group. - 1098-3600 .- 1530-0366. ; 23:1, s. 47-58
-
Tidskriftsartikel (refereegranskat)abstract
- Purpose: Stringent variant interpretation guidelines can lead to high rates of variants of uncertain significance (VUS) for genetically heterogeneous disease like long QT syndrome (LQTS) and Brugada syndrome (BrS). Quantitative and disease-specific customization of American College of Medical Genetics and Genomics/Association for Molecular Pathology (ACMG/AMP) guidelines can address this false negative rate.Methods: We compared rare variant frequencies from 1847 LQTS (KCNQ1/KCNH2/SCN5A) and 3335 BrS (SCN5A) cases from the International LQTS/BrS Genetics Consortia to population-specific gnomAD data and developed disease-specific criteria for ACMG/AMP evidence classes-rarity (PM2/BS1 rules) and case enrichment of individual (PS4) and domain-specific (PM1) variants.Results: Rare SCN5A variant prevalence differed between European (20.8%) and Japanese (8.9%) BrS patients (p = 5.7 x 10(-18)) and diagnosis with spontaneous (28.7%) versus induced (15.8%) Brugada type 1 electrocardiogram (ECG) (p = 1.3 x 10(-13)). Ion channel transmembrane regions and specific N-terminus (KCNH2) and C-terminus (KCNQ1/KCNH2) domains were characterized by high enrichment of case variants and >95% probability of pathogenicity. Applying the customized rules, 17.4% of European BrS and 74.8% of European LQTS cases had (likely) pathogenic variants, compared with estimated diagnostic yields (case excess over gnomAD) of 19.2%/82.1%, reducing VUS prevalence to close to background rare variant frequency.Conclusion: Large case-control data sets enable quantitative implementation of ACMG/AMP guidelines and increased sensitivity for inherited arrhythmia genetic testing.
|
|
| 15. |
- Zetterling, Carl-Mikael, et al.
(författare)
-
SiC MISFETs with MBE-grown AlN gate dielectric
- 2000
-
Ingår i: Materials Science Forum. - : Trans Tech Publications Inc.. - 0255-5476 .- 1662-9752. ; 338-342, s. 1315-1318
-
Tidskriftsartikel (refereegranskat)abstract
- Metal-Insulator-Semiconductor Field Effect Transistors (MISFETs) with ion implanted source and drain junctions have been made in 6H silicon carbide (SiC). Aluminum nitride (AlN) was used as the insulating gate dielectric, and was grown using molecular beam epitaxy (MBE). Gate controlled transistor operation was shown with an inversion layer mobility of 10-20 cm2/Vs. However, due to relaxation of the AlN film, the gate leakage was excessive, which precluded a thorough investigation of the transistor characteristics. This paper describes the manufacturing process and current voltage characteristics, and an improved process sequence is also proposed.
|
|
